sexual or food deception? deconstructing the floral mimicry of cephalanthera rubra (orchidaceae)

Sexual or food deception? Deconstructing Sexual or food deception? Deconstructing the floral mimicry of the floral mimicry of Cephalanthera rubra Cephalanthera rubra

(Orchidaceae)(Orchidaceae)

• Orchidaceae has a vast array of pollination strategies and pollinators1

• Attraction of pollinators:

Reward

Deception

• 1/3 of the estimated 25,000 species are thought to be pollinated by

deceit1,2

• In Europe, 80% of the allogamous species are deceptive3

(1) Van der Pijl & Dodson 1969, (2) Ackerman 1986, (3) Paulus 2005

2

• Sexual deception – insect males seeking for mates Olfactory cues: central role in attracting males1,2

Visual cues: increase attraction of males3 or not4

• Food deception – food-foraging insects Visual cues: color as the main attractant5,6

Olfactory cues: no role5,6

(1) Schiestl 2005, (2) Ayasse 2006, (3) Spaethe et al. 2007, (4) Vereecken and Schiestl 2009, (5) Ackerman 1986, (6) Jersarkova et al. 2012

3

• Distribution: Europe, North Africa, and southwest Asia

• Flowers of this allogamous species do not produce nectar

• Pollinators: males of Chelostoma rapunculi1

• Flight activity of males is strongly associated with

bellflowers (Campanula), where they rest and seek for

nectar and mates

• Ch. rapunculi females are oligoleges on Campanula

4(1) Nilsson 1983

• Ce. rubra flowers mimic color of Campanula and thereby

attract males of Ch. rapunculi1

• Rendezvous attraction: Females not observed

• Experiments testing attractiveness of floral cues of Ce.

rubra against those of Campanula were not performed

• Possible role of floral scents was neglected

• Are females really not attracted to Ce. rubra flowers or

are they only less frequent than males?

(1) Nilsson 1983

5

• To re-evaluate the kind of floral mimicry involved in this deceptive system:

1. Only males visit flowers:

a) Hypothesis 1: sexual deception

b) Hypothesis 2: rendezvous attraction

2. Females do visit flowers:

a) Hypothesis 3: food deception

6

• Bioassays with 1) Ch. rapunculi virgin females extracts 2) orchid flower extracts and 3) pentane (control) in a flight cage

• Extracts applied on bee dummies

• Male reactions recorded for 3 minutes - Approach: flight of the males towards the dummy - Pouncing: antennal inspection - Mounting: male mounts on the dummy - Copulation: copulation attempt

7

Re

spo

nse

of

ma

les

approach pouncing mounting copulation

ControlCe. rubra flower extractVirgin Ch. rapunculi

cuticle extract

*

Mann-Whitney U-test, Benjamini-Hochberg correction, *: P<0.058

Flowers of Ce. rubra do not mimic sex pheromones of Ch. rapunculi females

Hypothesis 1: Sexual deception

Ca. trachelium Ce. rubra

• Two-choice bioassays: Olfactory cues

1,5 m

PumpPump9

30 minFlower-naive bees


1,5 m 10

• Two-choice bioassays: Visual cues



1,5 m


11

• Two-choice bioassays: Visual + olfactory cues

PumpPump

Binominal test, P > 0.05

00009_xvid.avi

And in the nature?

• Three days of observation - eight females carrying pollinia

UV Violet - blue Green - yellow Orange - red

14

• Bee colour hexagon The color locus of Ce. rubra flowers

is within the Campanula color space

Colour locus of Ce. rubra flowers

resemble that of more Campanula

spp. than any of the Campanula spp.

16

• Headspace samples of 11 Campanula species and Ce. rubra

• Species-specific scent pattern (ANOSIM; Global R=0.99, P<0.001)

• MDS with all compounds (ca. 150)

Milet-Pinheiro et al. 2013. Journal of Chemical Ecology

17

a: (E)-β-ocimene + phenylacetaldehyde + 1,6-dioxaspiro[4.5]decane b: (E)-Conophthorinc: 2-nonanone + guaiacol + terpinolene + (E)-linalool oxide (furanoid)d: linalool + nonanal (artifact as also present in ambient controls) e: 2-phenylethanol f: (E)-2-methyl-1,7-dioxaspiro[5.5]undecane +(E)-7-ethyl-1,6-dioxaspiro[4.5]decane g: decanal (artifact as also present in ambient controls) + methyl salicylate h: 2-phenylethyl acetate i: α-copaenej: geranyl acetone

18

• Species-specific scent pattern (ANOSIM; Gl. R=0.94, P<0.001)

• MDS only with EAD-active compounds (16)1

Ce. rubra mimics Campanula compounds that are perceived by Ch. rapunculi bees

Which compounds specifically?



19

a: (E)-β-ocimene + phenylacetaldehyde + 1,6-dioxaspiro[4.5]decane b: (E)-Conophthorinc: 2-nonanone + guaiacol + terpinolene + (E)-linalool oxide (furanoid)d: linalool + nonanal (artifact as also present in ambient controls) e: 2-phenylethanol f: (E)-2-methyl-1,7-dioxaspiro[5.5]undecane + (E)-7-ethyl-1,6-dioxaspiro[4.5]decane g: decanal (artifact as also present in ambient controls) + methyl salicylate h: 2-phenylethyl acetate i: α-copaenej: geranyl acetone


20



21



22

a: (E)-β-ocimene + phenylacetaldehyde + 1,6-dioxaspiro[4.5]decane b: (E)-Conophthorinc: 2-nonanone + guaiacol + terpinolene + (E)-linalool oxide (furanoid)d: linalool + nonanal (artifact as also present in ambient controls) e: 2-phenylethanolf: E-2-methyl-1,7-dioxaspiro[5.5]undecane +E-7-ethyl-1,6-dioxaspiro[4.5]decane g: decanal (artifact as also present in ambient controls) + methyl salicylate h: 2-phenylethyl acetate i: α-copaenej: geranyl acetone


23

a: (E)-β-ocimene + phenylacetaldehyde + 1,6-dioxaspiro[4.5]decane b: (E)-Conophthorinc: 2-nonanone + guaiacol + terpinolene + (E)-linalool oxide (furanoid)d: linalool + nonanal (artifact as also present in ambient controls) e: 2-phenylethanolf: E-2-methyl-1,7-dioxaspiro[5.5]undecane +E-7-ethyl-1,6-dioxaspiro[4.5]decane g: decanal (artifact as also present in ambient controls) + methyl salicylate h: 2-phenylethyl acetate i: α-copaenej: geranyl acetone

Major compound of Ce. rubra, which is produced by 10 Campanula spp.


24

a: (E)-β-ocimene + phenylacetaldehyde + 1,6-dioxaspiro[4.5]decane b: (E)-Conophthorinc: 2-nonanone + guaiacol + terpinolene + (E)-linalool oxide (furanoid)d: linalool + nonanal (artifact as also present in ambient controls) e: 2-phenylethanol f: E-2-methyl-1,7-dioxaspiro[5.5]undecane +E-7-ethyl-1,6-dioxaspiro[4.5]decane g: decanal (artifact as also present in ambient controls) + methyl salicylate h: 2-phenylethyl acetate i: α-copaenej: geranyl acetone

The spiroacetal more commonly produced by Campanula (9 spp.).

Only mixture of spiroacetals (including E-conophthorin) attracts host-naive males and females of Ch. rapunculi1

• Ce. rubra is not pollinated by sexual deception

• Orchid flowers mimic visual and olfactory cues of Campanula flowers to attract both males and females of Ch. rapunculi

• Rendezvous attraction and food deception

• Role of floral scent in food-deceptive flowers may have been frequently underestimated.

25

Thanks to…

• Rebecca Scholz (Ulm)• Team of Botanical Garden in Ulm • Student helpers• German Science Foundation (DFG)

26

sexual or food deception? deconstructing the floral mimicry of cephalanthera rubra (orchidaceae)

Documents