floral biology of hesperantha crocoideae): how minor shifts in floral

ANN. MISSOURI BOT. GARD. 91: 186–206. 2004.

FLORAL BIOLOGY OFHESPERANTHA (IRIDACEAE:CROCOIDEAE): HOW MINORSHIFTS IN FLORALPRESENTATION CHANGETHE POLLINATION SYSTEM1

Peter Goldblatt,2 Ingrid Nanni,3 PeterBernhardt,4 and John C. Manning5

ABSTRACT

Field observations, floral dissections of a representative range of Hesperantha species, and pollen load analyses ofinsects captured on many of them indicate that flowers of this African genus are cross pollinated by a relatively broadrange of insects. The pollination ecology of Hesperantha can be divided into four overlapping systems that exploitinsects of four orders (Coleoptera, Diptera, Hymenoptera, and Lepidoptera). Species of the H. falcata type have erector nodding, salver-shaped, strongly fragrant, white flowers that open in the mid to late afternoon and evening and arepollinated by long-tongued apid bees and/or noctuid moths. Species of the H. pauciflora type have a virtually identicalfloral morphology, but the perianth is yellow or pink to mauve or blue and the flowers are usually unscented and areopen during the day, closing between midday and late afternoon, ca. 16:30 H. Flowers of this type are also pollinatedby apid bees, but in the southern African winter-rainfall zone other effective pollinators include nemestrinid flies(Prosoeca) with relatively short probosces and hopliine scarab beetles. In H. latifolia type flowers the perianth is pinkto magenta or red (rarely pale yellow), odorless, opens during the day but has an elongate perianth tube exceeding 18mm in length. These flowers are pollinated mainly by long-proboscid flies in the genera Prosoeca and Stenobasipteron(Nemestrinidae) or Philoliche (Tabanidae), but the red flowers of H. coccinea are pollinated by a guild of large butterfliesincluding Papilio and the satyrid Aeropetes. Lastly, H. vaginata has odorless and nectarless, short-tubed yellow flowers,usually with contrasting dark markings, that open only during the day and are pollinated exclusively by the hopliinescarab beetle, Clania glenlyonensis. The taxonomic distribution of plant species with these pollination systems makesit clear that shifts in pollination systems have occurred repeatedly across Hesperantha, although floral morphology andnectar biochemistry are relatively conservative. Whether flowers are nocturnal, crepuscular, or diurnal, only four vari-ables affect the floral ecology: length of the perianth tube, presence or absence of floral fragrance, timing of anthesis,and the closely associated trait of perianth color. Thus, species with pink, magenta, red, or yellow flowers close at nightand are rarely fragrant, whereas those with white or pale yellow flowers are nearly always fragrant and either open latein the day or only at sunset and remain open for most of the night. Species show considerable variation in nectarvolume and sugar concentration, closely correlated with pollination system, while two long-tubed species with floralcharacters typical of long-proboscid fly pollination produce no nectar and are inferred to be Batesian or guild mimicsthat achieve pollination by deception.

Key words: bees, floral ecology, Hesperantha, hopliine beetles, Iridaceae, long-proboscid flies, nectar, pollinationsystems, settling moths.

The radiation and diversification of the AfricanIridaceae depend to a greater or lesser extent onthe plasticity of pollination mechanisms, and all thelarger genera of the family exhibit a wide range offloral adaptations and correlated sets of insect oravian pollinators (Bernhardt & Goldblatt, 2000).

1 Support for this study by grants 5408-95, 9554-97, and 6704-00 from the National Geographic Society is gratefullyacknowledged. We thank Robert Brooks, Holger Dombrow, Douglas Kroon, H. Kruger, and Kim E. Steiner for theirhelp with the identification of insects; Margo Branch and John Manning for the illustrations; John Donaldson and hisgroup for sharing field facilities at Nieuwoudtville; Neil MacGregor for allowing us to conduct our research on hisproperty; and Cameron McMaster and Lendon Porter for assistance with fieldwork. Collecting permits were providedby the Nature Conservation authorities of Mpumalanga, Western Cape and Northern Cape Provinces, South Africa.

2 B. A. Krukoff Curator of African Botany, Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A. [email protected].

3 National Botanical Institute, P. Bag. X7, Claremont 7735, South Africa. [email protected] Department of Biology, St. Louis University, St. Louis, Missouri 63103, U.S.A. [email protected] Compton Herbarium, National Botanical Institute, P. Bag. X7, Claremont 7735, South Africa. manning@nbict.

nbi.ac.za.

For example, Lapeirousia is pollinated by long-pro-boscid flies, or bees and butterflies, or moths (Gold-blatt et al., 1995). Romulea exploits scarab beetles,pollen-collecting bees or, in at least two species,long-proboscid nemestrinid flies (Goldblatt et al.,1998a; Manning & Goldblatt, 1996, and unpub-

Volume 91, Number 12004

187Goldblatt et al.Floral Biology of Hesperantha

lished). The majority of species of Gladiolus appearto be pollinated primarily by nectar-feeding apidand anthophorine bees (Goldblatt et al., 1998b),but some red-flowered species are pollinated by thelarge butterfly Aeropetes (Johnson & Bond, 1994),while others are dependent on andrenid bees, acombination of bees and hopliine beetles (Goldblattet al., 1998a), long-proboscid flies, moths, or birds(Goldblatt & Manning, 1998; Goldblatt et al., 1999,2001).

Hesperantha, a mid-sized genus of subfamilyCrocoideae (syn. Ixioideae), comprises approxi-mately 80 species (Goldblatt, 1984, 1986, 1987,1993, 2003; Hilliard & Burtt, 1986; Goldblatt &Manning, 1996) distributed from the southern tipof Africa through the eastern African mountains asfar north as Ethiopia and Cameroon. Diversity isgreatest in southern Africa, where there are twocenters of diversity and regional endemism: theDrakensberg of South Africa and Lesotho; and thewest coast and near interior of Northern Cape andWestern Cape Provinces of South Africa. Comparedwith the approximately 260 species of Gladiolus,the 50 species each of Ixia or Watsonia, or the 40species of Lapeirousia, Hesperantha species have aconservative floral morphology. The relatively smallflowers (tepals typically 10–25 mm long, exception-ally to 37 mm) are radially symmetric, have sube-qual tepals, and are arranged in slender to compactspicate inflorescences. The flowers of most specieshave a symmetrical androecium and a style thatdiverges at the mouth of the floral tube into threelong, spreading branches. Interspecific floral vari-ation is restricted to perianth tube length and de-gree of curvature, perianth color (uniformly whiteto cream vs. various shades of pink to purple, oryellow, sometimes with dark markings), the pres-ence or absence of fragrance, the type of floral odor,and the timing of anthesis (Goldblatt, 1984, 2003).

A particularly unusual aspect of floral variationwithin this genus is the close linking of floral pig-mentation with the presence of floral odor and tim-ing of anthesis. White- or cream-flowered speciesof the southern African winter-rainfall zone are cre-puscular or nocturnal and produce a strong floralfragrance, whereas species with flowers of othercolors, and the white-flowered species of easternsouthern Africa, are typically odorless, at least tothe human nose. Field studies of the pollinationsystems of a selection of Hesperantha species wereundertaken to define and compare intragenerictrends in the evolution of pollination mechanismsand the function(s) of floral traits.

MATERIALS AND METHODS

INFLORESCENCE PHENOLOGY AND FLORAL LIFE

SPAN

Direct observations are presented on 34 Hesper-antha species made in the field from 1993 to 2002(Table 1) and supplemented by living collections atKirstenbosch Botanic Gardens, Cape Town, and theMissouri Botanical Garden, St. Louis. Observationswere made in the southern spring, summer, or au-tumn at sites in southern Africa (August to April).Observations of insect foraging involved 4 to 10hours per plant species (or occasionally more) andincluded recording of floral attractants (pigmenta-tion, scent), rewards (nectar), the mode and timingof anthesis (opening of individual buds), daily phe-nology, anther dehiscence patterns, expansion ofstigmatic lobes, the behavior of insects on the flow-er, and the taxonomic diversity of floral foragers.Floral scent was noted in the field and in cultivatedplants. Scents too weak to be immediately dis-cerned by the human nose were recorded after in-dividual flowers were picked and placed in clean,lidded glass jars and stored in a warm place. Thecontents of each jar was smelled after a minimumof 60 minutes (Buchmann, 1983). Plant voucherspecimens are deposited in the herbaria at the Mis-souri Botanical Garden (MO) and Kirstenbosch Bo-tanic Gardens (NBG) (Table 1).

COMPATIBILITY

Compatibility relationships were examined intwo species, Hesperantha quadrangula and H. pal-lescens, both maintained in the laboratory and iso-lated from possible pollinators. Fruit and seed setwere compared in five hand-selfed flowers and fiveflowers crossed with pollen of another individual ofthe same species. In the Iridaceae hand-selfing ofas few as five flowers is usually sufficient, as resultsare seldom mixed. Either all self crosses result inseed set or none do. Likewise, xenogamous crossesalways succeed.

NECTAR ANALYSIS

Nectar volume measurements were taken pri-marily from unbagged flowers in the field, soon afterthey opened, reflecting both rates of secretion anddepletion. To collect nectar, mature flowers werepicked and nectar was withdrawn from the base ofthe perianth tube with 3 ml capillary tubes afterseparating the ovary from the perianth base. Thepercentage of sucrose equivalents in fresh nectarwas measured in the field or laboratory using a Bel-lingham and Stanley hand-held refractometer (0–

188 Annals of theMissouri Botanical Garden

Table 1. Study sites and voucher information for Hesperantha species studied. Vouchers are housed at MO (Goldblatt& Manning) or at NBG (other collectors). All study sites are in South Africa.

Species Study site Voucher

H. acuta (Lichst. ex Roem. & Schult.) KerGawl.

Western Cape, foot of Vanrhyn’s Pass Goldblatt & Manning 11070

H. bachmannii BakerH. baurii BakerH. brevicaulis (Baker) G. J. Lewis

Glenlyon, NieuwoudtvilleFree State, The SentinelMpumalanga, God’s Window

Goldblatt & Nanni 11152Goldblatt & Manning 11051Goldblatt 72

H. coccinea (Backh. & Harv.) Goldblatt & J.C. Manning

site 1site 2site 3

Mpumalanga, near Lunsklip fallsKwaZulu-Natal, KarkloofKwaZulu-Natal, Highmoor

Goldblatt s.n. no voucherGoldblatt & Nanni 11242Goldblatt & Nanni 11249

H. cucullata KlattH. erecta (Baker) Benth. ex Baker

Northern Cape, NieuwoudtvilleWestern Cape, Vredenburg

Goldblatt 3954Goldblatt & Manning 11084

H. falcata (L. f.) Ker Gawl.site 1site 2

Western Cape, near DarlingWestern Cape, Caledon, Drayton

Goldblatt & Nanni 11096Goldblatt 11161

H. fibrosa BakerH. flava G. J. LewisH. flexuosa KlattH. grandiflora G. J. LewisH. huttonii (Baker) Hilliard & BurttH. lactea Baker

Western Cape, Fairfield, NapierWestern Cape, near MatjesfonteinNorthern Cape, near SpringbokFree State, The SentinelEastern Cape, Kologha ForestKwaZulu-Natal, Inchanga

Goldblatt & Nanni 10251Goldblatt 6074Goldblatt & Porter 12086Goldblatt s.n. no voucherGoldblatt & Porter 12007Goldblatt & Nanni 11235

H. latifolia (Klatt) M. P. de VosH. leucantha BakerH. luticola GoldblattH. marlothii R. C. FosterH. oligantha (Diels) GoldblattH. pallescens Goldblatt

Northern Cape, KamiesbergFree State, The SentinelNorthern Cape, near MiddelposNorthern Cape, near NieuwoudtvilleNorthern Cape, HantamsbergWestern Cape, Piekeniers Kloof

Goldblatt & Manning 9723Goldblatt & Nanni 11232Goldblatt 6067Goldblatt 11403Goldblatt & Manning 10043Goldblatt & Nanni 11161

H. pauciflora G. J. Lewis (pink flowers)site 1site 2

H. pauciflora (yellow flowers)

Northern Cape, OorlogskloofNorthern Cape, near NieuwoudtvilleNorthern Cape, Papkuilsfontein south

of Nieuwoudtville

Goldblatt & Manning 9975Goldblatt s.n. no voucherGoldblatt 11102

H. pilosa (L. f.) Ker Gawl. (blue flowers) Northern Cape, Bokkeveld Mts. Goldblatt 6272H. pilosa (white flowers)

site 1site 2site 3

Western Cape, DarlingWestern Cape, Viljoen’s PassWestern Cape, Rooisand, Bot River

Goldblatt & Nanni 11162Goldblatt 11113Goldblatt 11148

H. pseudopilosa GoldblattH. pubinervia HilliardH. quadrangula Goldblatt

Northern Cape, near NieuwoudtvilleFree State, The SentinelNorthern Cape, near Middelpos

Goldblatt 11108Goldblatt & Manning 11052Goldblatt 11157

H. radiata (Jacq.) Ker Gawl.site 1site 2

Western Cape, MalmesburyNorthern Cape, near Nieuwoudtville

Goldblatt s.n. no voucherGoldblatt & Nanni 11104A

H. rivulicola GoldblattH. scopulosa HilliardH. similis (N. E. Br.) R. C. FosterH. spicata (Burm. f.) Ker Gawl.H. stenosiphon GoldblattH. sufflava GoldblattH. vaginata (Sweet) GoldblattH. woodii Baker

Northern Cape, near NieuwoudtvilleFree State, The SentinelMpumalanga, Long Tom PassWestern Cape, MalmesburyEastern Cape, Cathcart districtWestern Cape, MalmesburyNorthern Cape, Glenlyon FarmEastern Cape, Naude’s Nek

Goldblatt & Nanni 11104Goldblatt & Manning 9856Goldblatt & Manning 10480Goldblatt 11087BGoldblatt & Porter 12995Goldblatt & Nanni 11087Goldblatt 4035Goldblatt & Manning 11067



50%) from five or more individuals per population,unless fewer individuals were available. Additionalnectar samples were dried on Whatman filter paperno. 1 and sent to B.-E. van Wyk, Rand AfrikaansUniversity, Johannesburg, for HPLC nectar sugaranalysis.

INSECT OBSERVATION AND POLLEN LOAD ANALYSES

Behavior of insects on Hesperantha flowers wascarefully observed to see whether insects contactedanthers and stigmas while foraging. Insects ob-served probing the floral tube or brushing the an-thers or stigmas were captured and killed in a jarusing ethyl acetate fumes. Pollen was removed frominsects after specimens were pinned. To preventcontamination of the body of an insect with pollencarried by another in the same jar, each insect waswrapped in tissue as soon as it was immobilized byjar fumes. Body length and proboscis length of in-sects was recorded from captured specimens.Night-flying moths are difficult to capture simplybecause darkness makes them difficult to locate.Use of flashlights covered with translucent red cel-lophane paper for illumination significantly assistedobservation and capture. Capturing some insects(especially long-proboscid flies) at some sites ap-peared to reduce the population significantly, so wetherefore killed as few of these insects as necessaryto obtain specimens for identification and pollenload analysis.

Removal of pollen from an insect involved gentlyscraping pollen off the body with a dissecting nee-dle (see Goldblatt et al., 1998a, b). The residuefrom needle probes was collected on glass slidesand mounted in 1 to 2 drops of Calberla’s fluid(Ogden et al., 1974). In the case of long-proboscidflies, which are large insects, sites of pollen depo-sition are often quite discrete for each plant visited,and pollen species can often be identified withoutrecourse to microscopic examination due to pollencoloration and position. Pollen grains were identi-fied microscopically by comparison with a tempo-rary reference set of pollen grain slides made fromplants flowering at study sites. Hesperantha pollengrains are distinguished from co-blooming species,other than members of Iridaceae subfamily Crocoi-deae, by their large size, perforate-scabrate exine,and monosulcate aperture with prominent 2-bandedoperculum (Goldblatt et al., 1991).

Insect specimens were identified by R. W.Brooks, University of Kansas (Apidae), H. Dom-brow, Worms, Germany (Scarabaeidae), D. Kroon,Sasolburg, South Africa, and H. Kruger, TransvaalMuseum, Pretoria (Lepidoptera—moths), J. C.

Manning (Diptera, Lepidoptera—butterflies), andKim E. Steiner, National Botanical Institute, CapeTown (Mellittidae, Scarabaeidae). Voucher speci-mens are deposited at the Snow Entomological Mu-seum, Lawrence, Kansas.

RESULTS

INFLORESCENCE PHENOLOGY AND FLORAL LIFE

SPAN

Most Hesperantha species have an erect inflores-cence reaching a height of 5–30 cm, but a few spe-cies of rocky habitats and cliffs, including H. brev-icaulis and H. scopulosa, have weak, droopingstems and a nodding spike (Fig. 1). Individuals pro-duce one or, in some species, two or more, simplespicate inflorescences annually, and flowering isclosely synchronized within the same species orpopulation both seasonally and diurnally. Flowerbuds are arranged more or less helically along thespike (Goldblatt, 1984, 2003). In six species, in-cluding H. flava, H. humilis, and H. latifolia, theflowering stem is mostly or entirely subterranean sothat the flowers are borne close to ground level (Fig.1B). Flowering periods broadly subdivide into aspring season (August and September, or Octoberin a few species) in the southern African winter-rainfall zone or a summer–autumn season (Decem-ber to April) in the summer-rainfall zone (Table 2).This coincides with the period of optimal plantgrowth during or soon after the main rainy seasonfor the geographical area. A few species of the sum-mer-rainfall zone flower in early to late spring (Hil-liard & Burtt, 1986), sometimes before foliageleaves have been produced, but for logistical rea-sons we did not study these early flowering species.

The pattern of flower buds opening on an inflo-rescence is acropetal. In all Hesperantha species amature flower expands and closes again within 12hours at specific times characteristic of the speciesor population. White, cream, or pale yellow flowersof the southern African winter-rainfall zone are fra-grant (Table 2) and typically open in the mid to lateafternoon or at sunset and close at specific timesin the night, always before daylight (Table 3). Flow-ers of other colors, and white- to cream-floweredspecies of the summer-rainfall zone, are scentless(Table 2) and open either in the early morning (H.ciliolata, H. pilosa blue-flowered form, as well asmost pink-flowered species of eastern southern Af-rica) and close soon after midday, or open after themiddle of the day (H. pauciflora) and close beforesunset (Table 3). The red flowers of H. coccineaopen in the early morning and close shortly beforesunset. Examples of perianth color and form, re-


Table 2. Floral characteristics of Hesperantha species arranged according to flower type. Measurements of theperianth tube include the wider upper portion that accommodates the head of a long-tongued insect; 1 5 presence,2 5 absence, trace 5 amount too little to measure volumetrically; salver 5 salverform. White-flowered populations ofH. falcata and H. pilosa are listed in the first group, while yellow-flowered or blue-flowered populations respectivelyare included in the second group. Examples of flower color in Hesperantha species are available in Manning et al.(2002) and at http://www.mobot.org/MOBOT/Research/Hesperanthapollination.pdf.

SpeciesFlowershape

Flowercolor

Tubelengthmm Scent Nectar

Floweringtime

Hesperantha falcata groupH. acutaH. bachmanniiH. cucullataH. erectaH. falcata

(also see below)

salvernodding tubesalversalversalver

whitewhitewhitewhitewhite

8–118–107–98–107–9

yesyesyesyesyes

11111

Aug.–Sep.Aug.–Sep.Aug.–Sep.July–Sep.Aug.–Sep.

H. flavaH. flexuosaH. marlothiiH. pilosa (also see below)H. pseudopilosaH. quadrangulaH. radiataH. rivulicolaH. spicataH. sufflava

tube-salversalvernodding tubesalversalversalvernodding tubesalversalversalver

yellowwhitewhitewhitewhitewhitewhite to creamwhitewhiteyellow

20–267–9

ca. 129–108–10ca. 3

10–129–114–5

12–16

yesyesyesyesyesyesyesyesyesyes

11111

trace1111

June–JulyAug.–Sep.July–Aug.Aug.–Sep.Aug.–Sep.Sep.Aug.–Sep.Aug.–Sep.Aug.–Oct.July–Aug.

Hesperantha pauciflora groupH. bauriiH. ciliolataH. falcata

(also see above)H. fibrosaH. humilis

salversalversalver

salvertube-salver

pinkpinkyellow

pinkpink

8–104–57–8

7–918–22

noyesno

nono

trace1?

12

Jan.–Feb.Sep.Aug.–Sep.

Aug.–Sep.June–July

H. leucanthaH. lacteaH. luticola

salversalvertube-salver

pale pinkcreamy yellowwhite with large dark

marks on the tepals

10–157–8

30–45

nonono

11

trace

Jan.–Feb.Jan.–Feb.July–Aug.

H. pauciflora salver pink to purple, or yellow 6–8 no trace or1

Aug.–Sep.

H. pilosa (also see above)H. similis

salversalver

bluepink

7–94–5

nono

1trace

Aug.–Sep.Jan.–Feb.

Hesperantha latifolia groupH. brevicaulisH. coccineaH. grandifloraH. huttoniiH. latifoliaH. oliganthaH. pubinerviaH. scopulosaH. stenosiphonH. woodii

tube-salvertube-salvertube-salvertube-salvertube-salvertube-salvertube-salvertube-salvertube-salvertube-salver

pinkred (or pink)pink, anthers brownpale pinkpurplepurplesalmon-pinkpinkpink, anthers blackpink

22–30(25–)30–38

28–3222–3520–2725–3520–2532–4245–6033–40

nononononononononono

1111112211

Mar.–Apr.Dec.–MayJan.–Feb.Feb.–Mar.Aug.–Sep.Sep.Jan.–Feb.Feb.–Mar.Feb.–Mar.Feb.–Mar.

Hesperantha vaginata groupH. vaginata cup yellow with brown

markings5–7 no 2 Aug.–Sep.

Unplaced speciesH. pallescens tube-salver pale yellow 18–22 no 1 Sep.



Table 3. Contrasted timing of floral opening and closing in selected Hesperantha species. Only species for whichprecise information is available are included, and data are for study populations only (as in Table 1). Timing varieswithin populations according to weather conditions, and other populations of the same species may have differentopening and closing patterns. Flowers of H. scopulosa do not fully close and have the tepals fully expanded for alldaylight hours and partially so at night. N/a 5 not assessed.

Species Opening Closing Days open

White-, cream-, or pale yellow-flowered species

H. bachmanniiH. cucullataH. erectaH. falcata

16:00–16:30(15:00–)16:00–16:30(14:00–)15:00–15:30(12:30–)15:30–16:30

or 17:30–18:00

6:30–7:00(19:00–)20:00–20:30(17:00–)18:30–19:0021:00–21:30 or

after 2:00

4n/a4–54–5

H. flavaH. lacteaH. marlothiiH. pallescensH. pilosa (white-flowered)

16:00–17:0011:45–12:3017:00–17:308:00–8:30

17:30–18:00

n/a16:00–16:30

4:00–4:3018:30–19:00

3:30–4:30

n/an/an/an/a4

H. pseudopilosaH. quadrangulaH. radiata

sample 2H. rivulicolaH. spicataH. sufflava

(15:00–)18:00–18:3016:00–16:3018:00–18:3017:00–17:3016:15–16:4518:00–18:3015:30–16:00

after 0:0019:00–19:30

5:30–6:305:30–6:00

after 0:000:00–0:30

after 0:30

n/a3–46–7n/an/a4–54–5

Pink-, blue-, or deep yellow-flowered species

H. baurii 7:30–8:00or 11:00–11:30

11:30–12:00or 16:30–17:00

3–4

H. brevicaulisH. coccineaH. humilisH. oliganthaH. paucifloraH. pilosa (blue-flowered)H. vaginataH. woodii

ca. 11:007:30–8:008:00–9:00

n/a(13:00–)14:00–14:308:30–9:00

14:30–15:009:00–9:30

n/a18:00–19:0016:00–16:3014:00–14:3017:00–17:3012:30–13:0016:30–17:0014:00–14:30

n/a3–4n/an/an/an/an/an/a

produced in color, are available in Manning et al.(2002). Representative photographs of Hesperanthaflowers are also posted at the following URL to-gether with this article: http://www.mobot.org/MOBOT/Research/Hesperanthapollination.pdf.

A flower typically lasts four days before collapseof the perianth, but in a few species with a whiteperianth, flowers last six or seven days (e.g., Hes-perantha radiata, H. spicata), yet maintain the pat-tern of opening and closing at specific times (Table3). Flower buds on the same inflorescence opensequentially, usually one day apart; hence, theremay be three or four flowers open at any time onan inflorescence for species with flowers lastingfour days, but up to eight flowers open in speciesin which flowers last six or seven days. When flow-ers close, the tepals cloak the anthers and stigmascompletely. Ambient temperature influences anthe-sis. On cold (, 158C), heavily overcast, or misty

days, flowers may not open completely for the entireday or the normal timing of opening may be delayeduntil conditions are more favorable. The only ex-ception we have encountered is H. scopulosa, theflowers of which do not close completely, but thetepals half close at sunset, and re-open fully to be-come extended at 908 to the tube after 7:00 H thenext morning.

Flowers of all species studied are weakly protan-drous. The anthers dehisce longitudinally withinone to three hours after the tepals of a new budfirst unfold, but this depends to some extent onambient temperature and humidity (see above) andanthers dehisce later in the day under wet-coolconditions. The three stylar arms, the adaxial sur-faces of which comprise the stigmatic surfaces, areheld erect when the flower first opens but they di-verge later during the same day, in most speciesspreading outward below the erect or divergent an-


thers, coming to lie over the extended tepals. In allspecies the style divides at (or in a few speciesbelow) the mouth of the perianth tube into threelong, slender arms (a generic synapomorphy forHesperantha, see Goldblatt, 1984, 2003) that ex-tend between the filaments. Open flowers are typ-ically held erect to suberect with the tepals spread-ing horizontally with the stamens symmetricallydisposed. Anthers are developmentally extrorsewith loculicidal dehiscence, and the pollen adheresto the dehisced anther locules. The filaments twistslightly in the open flower so that the anthers cometo face inward or upward, depending on whetherthey are held erect (most species with colored te-pals), or are articulated on the filaments, each onelying horizontally, at right-angles to the filament(crepuscular or nocturnal species with white orcream tepals). Stamens and style branches areasymmetrically disposed and declinate in H. gran-diflora, the only species in the genus with a zygo-morphic flower.

Compatibility varies within the genus. Severalspecies have been reported to be self-compatible(Goldblatt, 1984) following hand-mediated self-pol-linations but with reduced fertility (Hesperanthabachmannii, H. cucullata, H. falcata). Mechanicalautogamy without apparent reduction in fertility oc-curred in H. acuta, H. erecta, H. latifolia, and H.pallescens in the absence of pollinators. Hesperan-tha pauciflora and H. radiata failed to set seed fol-lowing self-pollinations by hand. In the course ofthe present study, self-compatibility was estab-lished for H. quadrangula and confirmed for H. pal-lescens (Goldblatt, 1984).

NECTAR

Nectar glands, when present (Table 4), are sep-tal, as they are in the entire subfamily Crocoideae(Goldblatt, 1990, 1991; Goldblatt & Manning, un-published). Nectar is secreted from three minutepores at the top of the ovary (one per chamber)directly into the base of the perianth tube wherethe accumulated fluid is retained until removed bya foraging insect. In species with the lower part ofthe tube narrow and tightly enveloping the style, asmall amount of nectar may be present in the upperpart of the tube, presumably the result of capillaryaction. Measurable volumes of nectar are producedin most species (Table 4), and volume correlateswith tube length. The long-tubed flowers of Hesper-antha coccinea (tube 25–38 mm long) and H. gran-diflora (tube 28–32 mm long) produced the mostnectar (up to 4.1 ml in the latter in flowers undis-turbed by insects—the perianth had not fully ex-

panded when nectar was measured), while flowersof short-tubed H. baurii, H. falcata, H. fibrosa, H.pilosa, H. quadrangula, and H. radiata producedsmall amounts of measurable fluid (, 1.0 ml ofnectar). The smallest quantities of nectar are pro-duced by H. leucantha and H. baurii (less than 0.1ml in the last species). There is a negative corre-lation between the percentage of sugar solute inHesperantha nectar and nectar volume. Thus, spe-cies that secrete the greatest amount of fluid tendto produce nectars lowest in dissolved sugars (e.g.,H. brevicaulis, H. coccinea, H. grandiflora, and H.woodii), while H. falcata, H. pilosa, H. radiata, andH. spicata secrete less than 0.5 ml of fluid that con-tains 35% to 48% dissolved sugars. Among speciesthat secrete less than 0.5 ml, H. bachmannii ap-pears exceptional in having relatively dilute nectar,with a mean of 21.5% dissolved sugars.

Sugar analyses of Hesperantha flowers (Table 4)indicate that species examined for sugar composi-tion offer nectars that are sucrose rich. White-flow-ered species with flowers open in the late afternoonand evening, e.g., H. falcata, H. pilosa, H. radiata,and H. spicata, have nectar of unusually high sugarconcentrations, 40–50%, while H. baurii has nectarof 48% to . 50% sucrose equivalents. All the spe-cies with white flowers so far examined secrete nec-tar, although there are only trace amounts in H.quadrangula, but nectar presence or absence variesin species with flowers of other colors. The long-tubed flowers of H. pubinervia and H. scopulosa pro-duce no nectar at all.

FLORAL PRESENTATION AND POLLINATION SYSTEMS

Four overlapping pollination systems can be rec-ognized in Hesperantha. Comparative floral traits ofthe four main systems are summarized in Table 2.The pollination systems and associated floral traitsdo not necessarily reflect the natural relationshipsof species.

The Hesperantha falcata Group

In this group, of which Hesperantha falcata andH. cucullata are typical examples, the flowers arecrepuscular or nocturnal and mostly white to creamor exceptionally pale yellow, and the perianth issalver-shaped with horizontally extended tepals(Figs. 1A, 2A) or in three species, nodding (Figs.1D, 2B) with lightly reflexed tepals (H. bachmannii,H. marlothii, and H. radiata). The floral tube iscylindrical, expanding slightly near the apex, andhollow with a narrow, uniform diameter of about 1mm. The tube typically contains nectar in the lower1–3 mm. The perianth tube is usually slightly



Table 4. Nectar properties of Hesperantha species that produce measurable quantities of nectar (see Table 2). SD5 standard deviation, (n) 5 number of individuals sampled, Fru 5 fructose, Glu 5 glucose, n/a 5 not assessed. Nectarsugars were analyzed by B.-E. van Wyk (Rand Afrikaans University, Johannesburg, South Africa). Data marked withan asterisk are from Johnson and Bond (1994). For H. acuta and one population of H. falcata, nectar from three flowerswas pooled to obtain sufficient nectar to register a refractometer reading.

Hesperanthaspecies

Nectar (n)

Volume mlMean % sucrose

equivalents (6SD)

% Nectar sugars

Fructose Glucose Sucrose

MeanSucrose/

Glu 1 Fru(n)

H. acutaH. bachmanniiH. bauriiH. brevicaulis

0.4–0.8 (3)0.2–0.4 (8)trace to 0.1 (6)1.0–1.6 (3)

36 (pooled sample)21.5 (2.6)49–.5019.3 (1.5)

n/an/an/an/a

n/an/an/an/a

n/an/an/an/a

n/an/an/an/a

H. coccineasite 1site 2site 3*

H. cucullataH. falcata

2.4–3.7 (5)2.2–2.9 (10)1.9 (19)0.2–0.6 (8)

20.8 (1.6)15.4 (0.9)17.4 (n 5 11)40.6 (3.7)

n/an/a42n/a

n/an/a43n/a

n/an/a15n/a

n/an/a

0.18 (1)n/a

site 1site 2

H. fibrosaH. grandifloraH. huttoniiH. lactea

0.3–0.5 (3)0.2–0.5 (6)0.3–0.4 (4)2.8–4.1 (5)1.3–2.4 (8)0.1–0.6 (10)

32 (pooled sample)36.2 (3.5)21.3 (2.1)14.8 (1.0)13.7 (1.6)21.6 (3.6)

39n/a

24–25n/an/an/a

38n/a

15–28n/an/an/a

23n/a

47–61n/an/an/a

0.27 (1)n/a

1.17 (2)n/an/an/a

H. latifoliaH. leucanthaH. marlothiiH. oliganthaH. pallescens

0.7–1.1 (10)0.4–1.0 (4)1.4–2.2 (10)1.1–1.8 (5)0.8–1.2 (10)

28.5 (3.4)46.8 (1.0)35.9 (3.8)26.4 (3.9)35.5 (5.6)

23–29n/an/a

19–23n/a

24–30n/an/a

24–25n/a

41–53n/an/a

52–57n/a

0.94 (3)n/an/a

1.20 (2)n/a

H. pauciflora(pink flowers)(yellow flowers)

0.1–0.5 (5)

0.6–0.7 (10)

35.4 (1.7)

23.5 (2.4)

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/aH. pilosa (blue flowers)

(white flowers)site 2site 3

H. pseudopilosa

0.2–0.4 (5)0.1–0.5 (10)0.2–0.4 (3)0.2–0.5 (6)0.2–0.5 (2)

44.2 (1.9)35.7 (3.5)45.0 (6.1)44.8 (2.7)42.0–48.5

n/an/an/an/an/a

n/an/an/an/an/a

n/an/an/an/an/a

n/an/an/an/an/a

H. radiatasite 1site 2

H. rivulicolaH. spicataH. stenosiphonH. sufflavaH. woodii

0.2–0.4 (2)0.2–0.5 (3)0.2–0.5 (3)0.2–0.5 (2)4.2–6.5 (11)0.4–1.2 (10)1.2–1.8 (5)

n/a42.4 (3.9)48.0 (2.0)42–4517.5 (2.0)28.0 (2.6)18.1 (0.9)

11–20n/an/an/an/an/an/a



1.86 (3)n/an/an/an/an/an/a

shorter than the tepals, thus 7–16 mm long (Table2) compared to tepals 12–16 mm long, but the tubeis half again as long as the tepals in H. flava, 20–26 mm long, compared with tepals up to 16 mmlong.

Almost all white- to pale yellow-flowered speciesof the southern African winter-rainfall zone are cre-puscular or fully nocturnal (Table 3). The perianthopens in the late afternoon, typically after 16:00 Hor at sunset, and closes before sunrise. Hesperantha

pauciflora is an exception. A rare, pale yellow-flow-ered form of this otherwise pink-flowered species(Goldblatt, 2003) has the tepals opening soon aftermidday and closing before sunset. Hesperanthaquadrangula is unusual: its white flowers have anunusually short perianth tube, 2–3 mm, comparedto the tepals, 9–12 mm long, and they open at ca.16:00 H and close shortly after sunset but beforedark, ca. 19:00 H. The widespread and common H.falcata is notable for the varied times that flowers


Figure 1. Growth forms and plant habit in Hesperantha. —A. H. acuta. —B. H. humilis. —C. H. oligantha. —D.H. radiata. Scale bar 5 10 mm for A, B, and D; 15 mm for C. (Drawn by Margo Branch, Cape Town.)

of different populations open, some opening as ear-ly as 16:00 H, and others after 17:30 H, but in allpopulations we examined, the flowers remain openafter 21:00 H. In H. erecta, the perianth opens atca. 15:00 H.

The eastern southern African Hesperantha lac-

tea, H. hygrophila Hilliard & Burtt, H. inconspicua(Schltr.) G. J. Lewis, and H. rupestris N. E. Br. exR. C. Foster (the latter three not studied here) haveunscented, diurnal flowers with a white to creamperianth that are open for only a portion of the dayand close fully before sunset, between midday and



Figure. 2. Perianth types in Hesperantha. —A. H. sufflava. —B. H. radiata. —C. H. oligantha. —D. H. coccinea.—E. H. vaginata. Scale bar 5 10 mm. Shading code: dark stippling 5 purple (H. oligantha); light stippling 5 red(H. coccinea); vertical hatching 5 yellow; and solid black 5 brown (H. vaginata). Drawn by John Manning.

late afternoon depending on the species (Hilliard& Burtt, 1986; Goldblatt, 2003). Thus in all re-spects except perianth color they resemble moreclosely species of the next group, the H. paucifloragroup.

When open, the flowers of species belonging tothe Hesperantha falcata group produce a strong,sweet fragrance that is variable between, and some-times within, species. Scents range from light rose(H. quadrangula, H. rivulicola) to jasmine or fran-gipani (Plumeria) (H. cucullata, H. falcata—somepopulations; H. flexuosa, H. pilosa—some popula-tions), narcissus (H. spicata), acrid-musk (H. erecta,H. falcata—some populations; H. pilosa—somepopulations; H. sufflava), or sweet with a strongclove component (H. marlothii, H. radiata).

Hesperantha cucullata, H. pilosa, H. quadran-gula, H. rivulicola, H. sufflava, and sometimes H.falcata are actively visited by large-bodied apid

bees (Tables 5, 6) with probosces 3–10 mm long.Bees forage for both pollen and nectar soon afterthe flowers open in the late afternoon. The whiteflowers are conspicuous in the late afternoon light,and Anthophora species or Apis mellifera can oftenbe seen visiting the flowers of these species. Smallsettling nocturnal moths, mostly noctuids, and mostcommonly Heliotis armigera, but also species ofAdelidae, Drepanogynidae, Geometridae, and Pyr-alidae (Tables 5, 6), with probosces 4–12 mm longare common and active at or after sunset and inthe early evening in the southern African winter-rainfall zone, and regularly visit flowers of all thespecies we observed for pollinators after sunset (H.bachmannii, H. cucullata, H. falcata, H. marlothii,H. pilosa, H. pseudospicata, H. radiata, and H. ri-vulicola). Both bees and moths are polylectic for-agers, and individual bees were found to carry thepollen of co-blooming species (Table 6), including


Table 5. Length of mouth parts of insects captured on Hesperantha flowers, with perianth tube lengths. Measure-ments are ranges for the insect or plant populations studied.

Insect speciesMouth part

mm (n)Plants on whichinsect captured

Tube lengthmm

DipteraProsoeca ganglbauriP. ganglbauriP. peringueyiP. sp. nov. 2Stenobasipteron wiedemannii

27–30 (4)28–32 (4)20–25 (3)

ca. 9 (2)19–23 (3)

H. grandiflora, H. scopulosaH. woodiiH. latifoliaH. paucifloraH. huttonii

28–4235–3815–25

6–825–35

HymenopteraAmegilla capensisAnthophora diversipes

9–10 (3)6.5–8 (4)

H. bauriiH. cucullata, H. pauciflora, H. pilosa,

H. rivulicola,H. sufflava

8–106–12

12–16Apis mellifera 3–4 (10) H. baurii, H. cucullata, H. falcata 7–10

Lepidoptera [butterflies]

AeropetesPapilio demodocusP. nireus

ca. 30 (1)ca. 25 (1)22 (1)

H. coccineaH. coccineaH. coccinea

30–3830–3830–38

Lepidoptera [moths]

Agrotis segetumCeromitia sp.

ca. 11 (1)11–12 (7)

H. rivulicolaH. pseudopilosa, H. radiata,

H. rivulicola

8–118–12

Cucullia terensisDrepanogynis sp.D. dochmoleucaD. rufigrisea

ca. 12 (3)ca. 10 (1)ca. 7 (1)ca. 11 (1)

H. cucullata, H. pilosaH. rivulicolaH. pilosaH. bachmannii

7–108–119–108–10

Heliotis armigera 8–9 (6) H. bachmannii, H. cucullata, H. pseu-dopilosa, H. radiata

8–12

Nomophila noctuella 5–7 (6) H. cucullata, H. pseudopilosa, H. radi-ata

7–12

Perizoma artifexXylopteryx arcuata

ca. 4 (1)ca. 8 (2)

H. pilosaH. cucullata

9–107–9

Bulbinella (Asphodelaceae), Lachenalia (Hyacin-thaceae), Hermannia (Malvaceae), and Iridaceae(including Gladiolus, Moraea) in their scopae orcorbiculae and/or on various parts of their bodies.In contrast, only Hesperantha pollen was found onthe bodies of captured moths except for one visitingH. pilosa, but as there were no other obvious night-flowering species at most of our study sites this isnot surprising.

All moths captured while visiting Hesperanthaflowers settled on the inflorescence and crawledover the flowers. They carried pollen on the under-side of the wings, ventral part of the thorax, legs,and sometimes on the antennae and proboscis. Onemoth captured on Cyphia bulbosa (L.) P. J. Bergius(Campanulaceae) at our H. pilosa study site carriedpollen of that species as well as that of H. pilosa.Pollen loads were light, often only a few grains be-ing present. The bodies of moths are, however, poor

surfaces for carrying pollen, and it is not surprisingthat after capture in a net and transfer to a killingbottle very little pollen remained on their bodies bythe time they had been pinned and then examined.Moth activity was found to be at a maximum forthe first hour and a half after sunset, thus untilabout 20:30 H. After this we noted few, if any, mothvisits and we therefore did not continue our obser-vations. It is possible that other moth species be-come active later, as noted by Johnson et al. (1993)for Crassula fascicularis Lam. (Crassulaceae), butflowers of most crepuscular or nocturnal Hesper-antha species close before 1:00 H, exceptions be-ing H. marlothii, H. radiata, and H. rivulicola, theflowers of which remain open until dawn or day-light.

The pollination by small settling moths in Hes-perantha follows the pattern described by Johnson(1997) for species of the orchid genus Satyrium.



Johnson recorded a similar suite of moths visitingdifferent species of that genus at night: Heliotis ar-migera and Syngrapha circumflexa on S. bicorne(L.) Thunb. and Agrotis segetum on Satyrium ligu-latum Lindl. and S. stenopetalum Lindl. with thebutterfly Vanessa cardui also visiting S. ligulatumduring the day, a pattern paralleled in H. rivulicola.A high nectar sugar concentration of 40.1% wasalso noted for S. stenopetalum, which is comparableto the high nectar sugar concentrations we found inmost settling moth-pollinated species of Hesperan-tha.

Those white-flowered species with flowers open-ing at or after sunset, including Hesperantha flava,H. marlothii, and H. radiata, have not been seento be visited by bees. The long-tubed H. flava mayreceive visits from sphinx moths according to Vogel(1954), but while this is consistent with its longperianth tube (18–28 mm long), we assume thatVogel was only making a suggestion and did notobserve sphinx moths visiting the species. Amongthe white-flowered species of the winter-rainfallzone H. quadrangula is exceptional in having flow-ers that close at about sunset, that is, before mothsare normally active. Thus, although it has whiteflowers that open in the late afternoon, it is evi-dently not pollinated by moths.

The Hesperantha pauciflora Group

The Hesperantha pauciflora group (Table 2) in-cludes the common eastern southern African H.baurii, its allies, H. lactea, H. leucantha, H. similis,and several more, the western Cape H. pauciflora,and western Karoo H. humilis (Fig. 1B). The peri-anth coloration is usually pink to purple, but blueor mauve in some populations of H. pilosa and inH. ciliolata, and cream to pale yellow in H. lactea.Floral structure in this group is virtually identicalto that of the H. falcata group, but the flowers aretypically scentless (Table 2) and the tepals unfoldduring the day, often in the morning, and close atmidday or shortly thereafter (H. baurii, H. pilosa—blue form, H. similis), or in the early afternoon, thenclosing by 17.30 H (H. pauciflora). Hesperantha cil-iolata is exceptional in having fragrant flowers thatproduce an unusual acrid, musky scent reminiscentof that produced by some southern African speciesof the orchid genera Corycium and Pterygodium,and differing markedly from the sweet odors of spe-cies of the H. falcata group. Flowers of the H. pau-ciflora group produce small quantities of nectar,mostly 0.1–0.3 ml in volume (Table 4). Flowers ac-tively visited by bees may, however, contain no de-tectable nectar when sampled in the field. When

sampled later, after placing cut stems in water over-night, flowers yield nectar, indicating that visitinginsects may have removed all available nectar dur-ing their foraging, or alternatively insufficient waterwas available to plants to allow nectar production.

Species in this group are pollinated primarily bylarge-bodied female anthophorine bees or workerhoney bees foraging for pollen or nectar, or for bothrewards. Bees land on the flower and brush boththe anthers and stigma lobes as they crawl over theperianth while scraping pollen into their scopae orcorbiculae. Most apid bees, Amegilla, Anthophora,and most Apis mellifera workers captured on Hes-perantha flowers are polylectic foragers (Table 6),and individuals were found to carry the pollen ofco-blooming Fabaceae, Asphodelaceae, Hyacintha-ceae, Boraginaceae, and Iridaceae in their scopaeor corbiculae and on various parts of their bodies.Perhaps significantly, however, almost half the Apismellifera workers captured, 11 out of 26 individu-als, carried pure loads of Hesperantha pollen, in-dicating temporary floral constancy, unlike otherbees analyzed for their pollen loads (Table 6). Flow-ers of H. pauciflora are occasionally also visited bya relatively short-proboscid Prosoeca species, pres-ently undescribed (Table 6), which behave much asanthophorine bees in search of nectar.

Species of this group may also be visited by ho-pliine beetles, but the significance of these beetlescompared to bees visiting the same species is dif-ficult to assess. Hopliine beetles often visit a rangeof plant species with the large, brightly coloredflowers that are particularly suited to their activities(Picker & Midgely, 1996; Goldblatt et al., 1998b),which include assembly, competitive behavior, andcopulation. Nevertheless, it may be best to regardspecies visited by both bees and hopliine beetlesas exploiting both groups of pollinators.

The Hesperantha latifolia Group (Table 2)

The Namaqualand and western Karoo species,Hesperantha latifolia and H. oligantha, and theeastern southern African H. brevicaulis, H. gran-diflora, H. huttonii, H. scopulosa, H. stenosiphon,and H. woodii exemplify the third pollination cat-egory (Figs. 1C, 2C). In these species the flowersare odorless, have an elongate perianth tube 20–60mm long, and usually a pink to purple (rarely red)perianth. The tepals are shorter than the tube,mostly 15–25 mm long (exceptionally to 42 mm inH. scopulosa and to 38 mm in H. grandiflora), andspread horizontally, or are slightly cupped in H.stenosiphon and H. woodii. Exceptional in the groupand genus, H. grandiflora has the tube sharply bent


Table 6. Pollen load analysis of captured insects on Hesperantha species. Coleoptera: Scarabaeidae: Anisochelus,Anisonyx, Clania. Hymenoptera: Apidae: Allodape, Amegilla, Anthophora, Apis. Colletidae: Scrapter. Halictidae: Patel-lapis. Melittidae: Rediviva. Diptera: Nemestrinidae: Prosoeca, Stenobasipteron. Lepidoptera: Adelidae: Ceromitia. Dre-panogynidae: Drepanogynis. Geometridae: Perizoma, Xylopteryx. Noctuidae: Agrotis, Cucullia, Heliotis. Nymphalidae:Vanessa. Pieridae: Papilio. Pyralidae: Nomophila. Satyridae: Aeropetes. Sphingidae: Hippotion. Data for Hesperanthavaginata are from Goldblatt et al. (1998b) and those for H. latifolia are from Manning and Goldblatt (1996). Sitenumbers refer to study sites as indicated in Table 1.

Plant and insect taxon

Number of insects carrying pollen load(s)

Pollen from host flower alonePollen from host

flower plus other species

H. bauriisite 1

Amegilla capensis /

Patellapis sp. /

Rediviva nelii /

hopliine beetle 1hopliine beetle 21

00003

31613

site 2Apis mellifera 5 0

H. bachmanniiDrepanogynis rufigriseaHeliotis armigeraunidentified noctuid moth

111

000

H. brevicaulisStenobasipteron wiedemannii not captured

H. coccineasite 2

Papilio nireusPapilio demodocus

11

00

site 3Aeropetes tulbaghia 1 0

H. cucullataAnthophora praecox /

A. schulzei 1 / 1 ?

Apis melliferaCucullia terensisHeliotis armigeraNomophila noctuellaXylopteryx arcuata

0031432

1200000

H. erectaApis melliferaAnthophora rufidicaudis /

00

52

H. falcatasite 1

Apis mellifera 1 4site 2

(moths incl. Heliotis armigera seen but not captured)H. flexuosa

Anthophora praecox /

Apis mellifera00

22

H. grandifloraProsoeca ganglbauri 0 3

H. huttoniiStenobasipteron wiedemannii1 0 3

H. lacteaAllodape stellarum / 0 2

H. latifoliaProsoeca peringueyi 0 4



Table 6. Continued.





H. luticolaApis mellifera 0 2

H. marlothiiCuculia terensis 1 0(Hippotion celerio seen but not captured)

H. pauciflora (pink flowers)site 1

Apis melliferasite 2

Anisochelus inornatus1

Anthophora schulzei /

0

20

4

32

Prosoeca sp. nov.(yellow flowers)

Anisochelus inornatusAnthophora diversipes /

Apis mellifera

0

202

2

110

H. pilosa (blue flowers)Apis melliferaAnthophora schulzei /

Anthophora krugeri /

Anthophora diversipes /

(white flowers)

200

0

311

1Anthophora rufidicaudis /

Cucullia terensisDrepanogynis dochmoleucaPerizoma artifex

0211

200 (1 with no pollen)0

H. pseudopilosaCeromitia sp.Drepanogynis rufogriseaHeliotis armigeraHeliotis scutuligeraNomophila noctuella

21414

00 (1 with no pollen)0 (5 with no pollen)10 (2 with no pollen)

(Hippotion celerio was captured but did not contact style branches or anthers and carried no Hesperantha pollen)H. quadrangula

Apis melliferaAnthophora diversipes /

Scrapter sp. indet. /

Anisonyx ignitus

0000

2211

H. radiataCeromitia sp.Heliotis armigeraNomophila noctuella

211

000

H. rivulicolaAnthophora diversipes /

Agrotis segetumCeromitia sp.Drepanogynis sp.

0131

400 (1 with no pollen)0

(Vanessa cardui was not captured but individuals were seen to contact anthers and style branches on visits)H. scopulosa

Prosoeca ganglbauri 0 3H. similis

Amegilla capensis / 0 2H. stenosiphon

Apis mellifera1 3 2


Table 6. Continued.





H. sufflavaApis melliferaAnthophora rufidicaudis /

Anthophora krugeri /

Anisonyx ditusScrapter sp. nov. /

Scrapter aff. albitarsis /

000000

221322

H. vaginataClania glenlyonensis2 7 5

H. woodiiProsoeca ganglbauri 2 3

Total 74 105

1 5 more individuals seen but not captured.2 5 Lepisia sp. of Goldblatt et al. (1998b).

near the apex so that the flowers face to the side,with the tepals held more or less vertically. Thestamens and style branches of this species are uni-lateral with the anthers and style arms archingdownward. Flowers of the H. latifolia group typi-cally produce relatively large quantities of nectar(Table 4), mostly 1–4 ml in volume with concentra-tions ranging from 14.8 to 28.5% sucrose equiva-lents. Eastern southern African species have un-usually low nectar concentrations, less than 21%sucrose equivalents and with a mean as low as14.8% in H. grandiflora and 13.7% in H. huttonii.The flowers of H. scopulosa lack nectar, as do thoseof H. pubinervia (for which we have no pollinatorobservations). The long-tubed flowers of the rare H.pubinervia have an unusually narrow tube (Gold-blatt, 2003), which may not accommodate the pro-boscis of a long-proboscid fly.

Flowers of most species in the Hesperantha la-tifolia group are visited and pollinated exclusivelyby long-proboscid flies in the family Nemestrinidae.In the southern African winter-rainfall zone, thelong-tubed H. latifolia is pollinated by the nemes-trinid Prosoeca peringueyi, while H. oligantha andH. purpurea are inferred to be pollinated by a sec-ond and undescribed Prosoeca species, P. sp. nov.(see Goldblatt et al., 1995; Manning & Goldblatt,1996). Long-tubed species of the summer-rainfallzone, including H. grandiflora, H. scopulosa, andH. woodii, are pollinated by P. ganglbauri, whileH. brevicaulis and H. huttonii are pollinated byStenobasipteron wiedemannii. The elongated pro-bosces of these flies are typically slightly shorterthan the length of the perianth tubes of the Hes-perantha species that they visit (Table 5), but these

flies are the only insects that are able to forage onthe nectar held in the lower part of the perianthtube. While flowers of H. stenosiphon seem obvi-ously adapted for long-proboscid fly pollination, wefound no flies at our study site; instead, honeybeeswere visiting the flowers and collecting pollen. Indoing so they were seen transporting pollen fromanthers of one plant to style branches of another,effecting pollination.

An important exception in the Hesperantha la-tifolia group is the red-flowered form of the riverinespecies H. coccinea (Fig. 2D). This plant has twocolor morphs, the more common red-flowered formpollinated by a guild of large butterflies includingAeropetes tulbaghia (Satyridae) and Papilio species(Papilionidae). Visits by Aeropetes have also beenreported by Johnson and Bond (1994). Johnson(pers. comm.) has also seen an unidentified long-proboscid fly visiting the red-flowered form, but thishas been witnessed only once to date. The secondcolor form of H. coccinea has a pink perianth. Wehave no observations on visitors to the pink form.Its pink perianth may indicate a dependence onlong proboscid flies for pollination. Because onlyone color form of one species of Hesperantha ispollinated by large butterflies, it seems unreason-able to recognize an additional pollination group inthe genus.

Flies grasp the tepals with their tarsi and probefor nectar while continuing to vibrate their wings,contacting anthers and stigmas with the ventral orlateral parts of the head and thorax. In the case ofHesperantha grandiflora, pollen deposition is al-ways on the ventral part of the thorax because theunilateral stamens are positioned below the mouth



of the floral tube. Field observations and pollenload analyses show that all fly species visit openflowers of other species during foraging bouts andthat most of these species have morphologicallyconvergent flowers that may be regarded as belong-ing to specific pollination guilds. Thus, Prosoecaperingueyi visits a range of plants with intense redor violet flowers, including Pelargonium magen-teum J. J. A. van der Walt (Geraniaceae) and spe-cies of Iridaceae such as Babiana curviscapa G. J.Lewis, B. dregei Baker, and Lapeirousia silenoides(Jacq.) Ker Gawl. (Manning & Goldblatt, 1996), aswell as H. latifolia in the Kamiesberg of Namaqua-land. Likewise, Prosoeca ganglbauri visits severalpink-flowered species including Gladiolus micro-carpus G. J. Lewis (Iridaceae), Nerine bowdenii S.Watson (Amaryllidaceae), and Zaluzianskya micro-siphon (Kuntze) K. Schum. (Scrophulariaceae) dur-ing foraging bouts on H. grandiflora or H. scopulosain the northern Drakensberg.

The Western Cape Hesperantha pallescens is ex-ceptional in having pale yellow flowers with anelongate perianth tube with the flowers openingsoon after sunrise and closing before sunset. Theflowers conform to the model for species pollinatedby another long-proboscid fly, Philoliche (Tabani-dae) (Goldblatt et al., 1995; Goldblatt & Manning,2000). To date we have not located a study popu-lation at an undisturbed site where the predictedpollinator is active, and we have seen no insectvisitors to the species at our study site during ap-parently ideal conditions for insect activity.

Two patterns of butterfly behavior can result inpollen dispersal and pollen deposition. The first hasbeen described as ‘‘inspection visitation’’ by John-son and Bond (1994). A butterfly making an in-spection visit does not land or feed on a flower, butits comparatively long body and broad wings oftenbrush against the anthers and long style branchesor stigmas as it swoops close to an open flower be-fore moving to another, sometimes of the same spe-cies. In contrast, a true foraging visit requires thatthe butterfly actually grasp the tepals and insert itsproboscis into the floral tube. In doing so, the ven-tral surface of the thorax and proximal abdomenbecome dusted with pollen. Butterflies noted andcaptured visiting red-flowered Hesperantha cocci-nea include Papilio demodocus, P. nereis, and Aero-petes tulbaghia, the latter also reported by Johnsonand Bond (1994) to be a pollinator of this plant.

The Hesperantha vaginata Group

The Hesperantha vaginata group (Table 2) in-cludes only H. vaginata and H. karooica Goldblatt

(not studied), which have unscented, bright yellowflowers, often marked with bold splashes of con-trasting dark brown color (Fig. 2E). These flowershave a relatively short tube, 5–8 mm long, that pro-duces no measurable nectar. The tepals, 30–35 mmlong, much exceed the length of the tube. Theseflowers open during the middle part of the day, 13:00 H in H. vaginata, and close in the late after-noon, ca. 18:00 H in warm weather.

Hesperantha vaginata is visited exclusively bythe hopliine beetle Clania glenlyonensis (identifiedas Lepisia sp. 1 in Goldblatt et al., 1998b) (Table6). The flowers have the stereotyped adaptations forthe hopliine beetle pollination system, a large flow-er with spreading or somewhat cupped tepals, re-duced perianth tube, absence of nectar, and boldcontrasting pigmentation (so-called beetle marks)(Picker & Midgley, 1996; Goldblatt et al., 1998b;Steiner, 1998). Clania individuals spend a consid-erable time in a flower, either crawling about or atrest with their heads pointed toward the center forup to 20 minutes. Sometimes their visits may lastmuch longer, and beetles may even spend the nightin the closed flowers. Hopliine beetles use the flow-ers of H. vaginata and some other species growingnearby, including Romulea monadelpha (Sweet)Baker (Iridaceae) and Arctotis acaulis L. (Astera-ceae), as sites for assembly, intraspecific competi-tion, and mating. They are invariably covered witha combination of pollen of H. vaginata and the co-blooming species listed above. Although these bee-tles feed on pollen and sometimes on tepal tissue,they do little or no damage to flowers (Steiner,1998; Goldblatt et al., 1998b).

DISCUSSION

Pollination biology varies among Hesperanthaspecies but correlates closely with the mode of flo-ral presentation, timing of anthesis, and nectar se-cretion. Contrary to past predictions (Scott Elliot,1891; Marloth, 1915; Vogel, 1954), white-floweredspecies that have flowers opening in the late after-noon and remaining open at night are not exclu-sively pollinated by moths. Indeed, our studies ofthe floral biology of Hesperantha, incomplete asthey are, highlight the danger of inferring the pol-lination systems of plants with limited fieldwork orentirely from floral morphology. Marloth (1915:plate 42) suggested the genus was primarily polli-nated by moths, based on his observation of smallmoths (not identified) seen visiting H. falcata. Vogel(1954) carried this further in suggesting that long-tubed species including H. flava, H. grandiflora, H.longituba (by which he probably meant H. huttonii),


and H. pulchra were pollinated by sphinx moths.The last three species have odorless, pink flowersthat close at night. Vogel also speculated that theyellow and brown, short-tubed flowers of H. vagin-ata (which he knew as H. metelerkampiae) and thepink-flowered H. pauciflora were pollinated by bees(Vogel, 1954: 103). He was partly correct only inhis assessment of H. pauciflora, and possibly of H.flava, for which we await field observations.

At first glance the adaptive radiation of pollina-tion systems in Hesperantha parallels that found inlarger genera of the Iridaceae in southern Africa,but with an unusual emphasis on white flowersopening in the late afternoon or evening, a patternbest developed in the southern African winter-rain-fall zone. Specifically, Bernhardt and Goldblatt(2000) noted the number of pollination systems inan African genus of the Iridaceae correlates posi-tively with the number of species in the genus.Genera containing more than 100 species (e.g.,Gladiolus and Moraea) have the most diverse pol-lination systems exploiting up to eight broad cate-gories of pollen vectors. With the exception of Fer-raria (ca. 12 species) and Sparaxis (15 species),genera of Iridaceae with less than 20 species (e.g.,Micranthus, Nivenia) do not have more than twomodes of animal pollination (Goldblatt et al.,2000a; Bernhardt & Goldblatt, 2000; unpublisheddata). Hesperantha, with 79 species, Geissorhiza (85spp.), Ixia (ca. 50 spp.), and Lapeirousia (40 spp.)each have four or five major pollination modes(Goldblatt et al., 1995, 2000b; Bernhardt & Gold-blatt, 2000).

Four major modes of pollination (bee and cre-puscular settling moth; diurnal bee; hopliine beetle;long-proboscid fly, or large butterfly) are confirmedfor Hesperantha based on our field observations andcollection of floral foragers with analysis of theirpollen loads. A fifth mode of pollination by sphin-gid moths, predicted by Vogel (1954) for H. flava,remains to be confirmed by future field investiga-tion.

Furthermore, pollination systems in Hesperanthaalso subdivide along predictable modes of floralpresentation already described in other genera ofIridaceae. This is most striking in the H. latifoliagroup where tubular, odorless flowers with differentpatterns of floral pigmentation are pollinated by dif-ferent genera or species of two families of long-proboscid flies. As described in the genera Babi-ana, Gladiolus, and Lapeirousia, tubular flowersthat are pink to the human eye (e.g., H. brevicaulis,H. grandiflora, H. huttonii, H. woodii) are mostlikely to be pollinated by the Nemestrinidae Pro-soeca ganglbauri and Stenobasipteron wiedemannii.

In contrast, those with intense blue to purple flow-ers (e.g., H. latifolia, H. oligantha) are pollinatedby Prosoeca peringueyi or an undescribed Prosoceaspecies. Pale yellow to cream, tubular flowers aremore likely to be pollinated by long-proboscid ta-banids in the genus Philoliche (Goldblatt et al.,1995; Goldblatt & Manning, 2000; Manning &Goldblatt, 1996, 1997).

UNIQUE TRENDS IN THE FLORAL ECOLOGY OF

HESPERANTHA

Pollination systems incorporating large-bodiedbees, long-proboscid flies, or hopliine scarab bee-tles have been well described in 14 other generaof the Iridaceae of southern Africa and are not inany manner unusual in Hesperantha (Bernhardt &Goldblatt, 2000). There are, however, two modes ofpollination in this genus atypical of the family.First, pollination by deceit is suggested in the tu-bular, pink flowers of H. pubinervia and H. scopu-losa. While both species have the pigmentation andfloral tube length of nectariferous species pollinatedby long-proboscid flies, both fail to secrete nectar.As this mode of floral presentation is virtually iden-tical in co-blooming species pollinated by the sameflies, H. pubinervia and H. scopulosa evidently rep-resent either Batesian or guild mimics. These twomodes of deceit are more common in the Orchi-daceae (Dafni & Bernhardt, 1989), including thesouthern African genus Disa (Johnson, 1994; John-son et al., 1998). Second, our documentation of pol-lination mechanisms in the Hesperantha falcatagroup is the first record in the Iridaceae of specieseither exploiting both settling moths of five lepi-dopteran families with crepuscular to nocturnal for-aging habits and large-bodied apid bees (Antho-phora and Apis), or settling moths alone. Whilegeneralist pollination systems combining bees andLepidoptera have been described in a few speciesof Lapeirousia (Goldblatt et al., 1995), these speciesdepend on true butterflies and sometimes mothswith diurnal habits. In contrast, full floral presen-tation by species of the H. falcata group begins attwilight. Thus, while several species of the H. fal-cata group attract large-bodied bees, Gladiolus andLapeirousia species receive the majority of theirvisits from bee pollinators from mid morning to ear-ly afternoon, and their flowers often close at night.Bee pollination in the H. falcata group only beginsat the end of the day, and flowers remain open aftersunset to exploit a second group of pollinators thatbelong to another order of insects.

Other genera of the African Iridaceae in whichmoth pollination is known or inferred, Babiana (un-



published data), Gladiolus (Goldblatt et al., 2001;Goldblatt & Manning, 2002), and Lapeirousia(Goldblatt et al., 1995), have larger flowers with arelatively long perianth tube, and are visited eitherby hovering sphinx or noctuid moths with long pro-bosces. The foraging pattern in these species is un-like that shown by small moths on Hesperanthaflowers, in which individuals crawl over the inflo-rescence, visiting one flower after another beforemoving to another plant.

The dark red or brown pigmentation on the re-verse of the outer tepals of most otherwise white-flowered species of the Hesperantha falcata groupmay be a form of crypsis. When the perianth isclosed, only the outside of the outer tepals is visi-ble, and the dark color presumably camouflages theperianth from both herbivorous beetles and nectar-robbing bees. Johnson (1995) postulated a similarreason for the dark red color of the orchid Disa(Monadenia) ophyridea (Lindl.) Bolus, which is alsopollinated by noctuid moths. These flowers cannotclose fully, hence the heightened need for crypticcoloration to prevent nectar and pollen robbers. Inthis species moths evidently locate flowers solelyby olfactory cues.

At first glance, butterfly pollination in Hesper-antha coccinea appears to converge with the Aero-petes tulbaghia pollination system described byJohnson and Bond (1994). These authors have de-scribed a true guild of red-flowered species thatbloom primarily in the southern African winter-rainfall zone and are pollinated almost exclusivelyby the large satyrid butterfly A. tulbaghia. Thisguild includes several species in the Amaryllida-ceae and Iridaceae and is characterized by thelarge, bright red flowers, sometimes with white nec-tar guides, relatively narrow floral tubes and ample,but relatively dilute nectar. Although it occurs inthe southern African summer-rainfall zone, Hesper-antha coccinea appears to fit this profile, but moreimportant, it is not pollinated exclusively by Aero-petes, unlike the guild of large butterfly flowers inthe winter-rainfall zone. The pollination system ofH. coccinea also incorporates some of the largerspecies of butterflies in the family Papilionidae.Thus even though Aeropetes has a strong, innateattraction for red flowers, it is not the only visitorto red butterfly flowers in southern Africa. The lackof pollination by other large butterflies in the win-ter-rainfall zone may simply reflect the seasonalscarcity of other large butterflies there. We note thatother large butterfly flowers of the summer-rainfallzone include red-flowered species such as Bauhi-nia galpinii N. E. Br. (Fabaceae), Gloriosa superbaL. (Colchicaceae), as well as those of other colors

such as blue-flowered Plumbago auriculata Lam.(Plumbaginaceae). In eastern southern Africa Aero-petes seems to have a weaker affinity for red flowersand often visits yellow flowers of Kniphofia (Aspho-delaceae), in addition to the red flowers of plantssuch as Gladiolus saundersii J. D. Hook. (Goldblatt& Manning, 2000, 2002) as well as H. coccinea. Itis unlikely that red pigmentation and tubular flow-ers limit the access of large butterflies other thanA. tulbaghia in the classic definition of butterflypollination (Faegri & van der Pijl, 1979), in whichred pigmentation and a narrow floral tube are rel-atively common.

POLLINATION SHIFTS IN HESPERANTHA

With the exception of species of the Hesperanthafalcata group, pollination systems in this genus re-flect the exploitation of the usual range of southernAfrican insects responsible for pollination in thefamily. In contrast to other genera of Iridaceae,however, we also note that minimal shifts in floralcharacters are all that has been required to changea pollination system.

In particular, the morphological modification ofHesperantha flowers has been limited to the lengthof the perianth tube and the orientation of the te-pals at anthesis. This conservative trend must becompared to the shifts in the pollinations systemsof Moraea requiring severe changes in tepal ori-entation and differentiation of the inner and outertepals and in the morphology of the staminal col-umn and style branches (Goldblatt & Bernhardt,1999). We must also compare the relatively con-servative perianth morphology of Hesperantha withthat of Gladiolus in which floral symmetry and floraltube shape and orientation change with the primarypollinators (Goldblatt & Manning, 1998; Goldblattet al., 1998a). Instead, significant alterations of flo-ral presentation in Hesperantha are limited to rel-atively minor shifts in floral pigmentation, correlat-ed with variation in scent production and nectarsecretion. Indeed, to the human eye Hesperanthaflowers appear to lack the unusually complex, con-trasting patterning of pigmentation typical of theflowers of most other genera of the family in south-ern Africa.

Comparatively minor differences in nectar sugarcomposition and concentration have had a dramaticeffect on which insects are most likely to pollinatea Hesperantha flower, for the important reason thatthese biochemical characters evolved in associationwith shifts in the mechanics of floral phenology.Specifically, the stereotyped opening and closing oftepals in different species, at different seasons, and


at different times of the same day sharply restrictsforaging by prospective pollinators. Mature flowersthat remain closed while particular species of an-thophilous insects are actively searching for ediblerewards are almost as effectively excluded from de-veloping novel interactions as they would be if theybloomed at a time of the year when the same insectsare absent.

A change in pollinator from an insect with rel-atively short mouth parts, such as apid bees, short-proboscid nemestrinids, small moths, and possiblyother polyphagic taxa, to one with longer mouthparts, such as long-proboscid nemestrinids, mayseem a relatively moderate shift and merely one ofdegree. It must, however, be remembered that ashift to a long-proboscid fly pollinator means achange from a system where several species of beeand fly, or several different species of moth, maypollinate a species to one where only a single spe-cies is the primary or sole pollinator. Long-probos-cid flies are particularly effective pollinators of cer-tain plants because relatively few plants offer thema reliable source of nectar, and they usually carryheavy loads of pollen on specific parts of their bod-ies, limiting or avoiding stigma clogging (Goldblatt& Manning, 2000). The shorter-tongued insects,however, visit many species, sometimes in a non-constant pattern, and they usually carry mixedloads of pollen that are often randomly scatteredover their bodies. These contrasting patterns of pol-lination must have important consequences for thereproductive systems of the two plant groups. Ashift to a specialist pollination system using justone pollinator species presumably has importantconsequences for the radiation of a genus despitethe apparently trivial shift in morphology and phys-iology.

DISTRIBUTION OF POLLINATION SYSTEMS

In the absence of any phylogenetic hypothesesabout the radiation of Hesperantha, the origin andevolution of pollination systems in the genus re-mains a speculative topic. Small white, crepuscularor nocturnal flowers are unknown in subfamily Cro-coideae outside the genus, and this pollination sys-tem must be derived. Flowers in Geissorhiza, thegenus to which Hesperantha is most closely related(Lewis, 1954; Goldblatt, 1984; Reeves et al., 2001),may be pink, blue, violet, or white, but are alwaysdiurnal. The most common, and presumably ances-tral pollination system in Geissorhiza is a general-ized one (Nanni, unpublished data) in which thesmall, short-tubed flowers are open during the dayand offer both pollen and small quantities of nectar.

They are visited by a range of insects includingApis mellifera, hopliine beetles, butterflies, bee flies(Bombyliidae), and short-proboscid tabanid and ne-mestrinid flies, and these species may be consid-ered generalists. The pollination system in Hesper-antha that most closely resembles this system isthe large-bodied Apis mellifera–anthophorine bee,hopliine beetle, and short-proboscid nemestrinid flysystem found in the winter-rainfall zone H. pauci-flora, and the anthophorine bee system in sucheastern southern African species as H. baurii, H.lactea, and H. similis.

The long-proboscid fly pollination system in Hes-perantha is, we assume, derived, since it is a morespecialized system than those using a wider rangeof pollinators. The taxonomic distribution of thestrategy in the genus makes it clear that it has hadmultiple origins (Goldblatt, 2003). The easternsouthern African species pollinated by Prosoecaganglbauri or Stenobasipteron wiedemannii mayshare a common ancestry. However, the Namaqua-land H. latifolia, pollinated by Prosoeca peringueyi,and the western Karoo H. oligantha, inferred to bepollinated by an undescribed Prosoeca species, be-long to different taxonomic sections of Hesperantha(according to Goldblatt, 1984, 2003). Long-probos-cid fly pollination is also inferred for two apparentlyunrelated species of Hesperantha sect. Radiata, theeastern Cedarberg H. elsiae and the southern CapeH. muirii, based on flowers with an elongate peri-anth tube and pink coloration. These two speciesare most likely local derivatives of the widespreadH. radiata, the nocturnal flowers of which are pol-linated by moths. Thus, while we can say littleabout the origins of moth pollination in Hesperanthaflowers, it is clear that long-proboscid fly pollina-tion evolved several times in the genus and involvesdifferent species of nemestrinid (and possibly ta-banid) flies across the range of the genus in south-ern Africa. This mirrors the pattern in Gladiolus(also belonging to the Crocoideae), in which long-proboscid fly pollination may have evolved at least10 and possibly 12 times in this genus of 165 spe-cies in southern Africa (Goldblatt & Manning,1999; Goldblatt et al., 2001).

The shift to butterfly pollination in red-floweredpopulations of Hesperantha coccinea is unique inthe genus. Although butterflies may share this riv-erine species with long-proboscid flies, it seemslikely that only the rare pink-flowered populations,which Occam’s razor suggests must be ancestral,are normally pollinated by long-proboscid flies. Thered-flowered populations, which extend from theAmatola Mountains in Eastern Cape Province,South Africa, to Zimbabwe, are pollinated largely,



if not exclusively, by a range of large butterflies,including species of Papilionidae and the satyridAeropetes.

The shift to exclusive hopliine beetle pollinationin Hesperantha vaginata (and perhaps its close allyH. karooica) is likewise unique in the genus, butflowers shared by apid and anthophorine bees andhopliines occur in a few other species of Hesper-antha, notably H. pauciflora. The evolution of astrictly hopliine pollination system is thus not par-ticularly surprising.

In summary, the radiation of pollination systemsin Hesperantha, a mid-sized genus of subfamilyCrocoideae of the Iridaceae, is not unexpected inview of the diversity of pollination systems in mostother genera of any size in the subfamily. Each ge-nus, however, appears to exploit the available spec-trum of pollinators in different ways and to differentdegrees. Ixia exhibits a remarkable pattern of ra-diation based on hopliine beetle pollination andsecondarily on long-proboscid flies, whereas Glad-iolus exploits in particular anthophorine bee polli-nation, with secondary emphasis on long-proboscidflies, Lepidoptera, or passerine birds. Lapeirousiahas exploited a range of different long-proboscidflies as pollinators, while a few species have flowersadapted for sphinx or other moth pollination, butsome species are pollinated by a combination ofbees, wasps, and butterflies.

The pattern of radiation in Hesperantha showsparticularly marked exploitation of long-proboscidfly pollination in eastern southern Africa, where 11of the 34 species there (Goldblatt, 2003) have flow-ers that display the typical adaptations for thisstrategy. In contrast, species of the southern Africawinter-rainfall zone have exploited small moth pol-lination (or a combination of moths and apid andanthophorine bees) at the expense of most otherpollination systems. Hopliine beetle, exclusive an-thophorine bee, and long-proboscid fly systems arelimited to only a few species there. Some 22 of the44 species in the winter-rainfall zone have beenshown herein, or may confidently be inferred, tohave this small settling moth pollination system,often associated with foraging by large anthophor-ine bees late in the day, a system not otherwiseknown in the Iridaceae.

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Figure 3. The principal flower types in Hesperantha. A. H. pauciflora (typical bee flower with relatively short perianth tube, pink color, and open in the day). B. H. cucullata (typical settling moth flower with relatively short perianth tube, white color with reddish pigment on outside of outer tepals, opening near sunset and lasting into the night). C. H. woodii (long-proboscid fly flower with elongate perianth tube, pink perianth, open during the day). D. H. vaginata (beetle flower with vestigial tube, cupped perianth, brightly colored with contrasting markings, open in middle of the day) with hopliine beetle Clania glenlyonensis in the flower.

A. B.

C. D.

floral biology of hesperantha crocoideae): how minor shifts in floral

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