Reproductive ecology and conservation of the rare Dictamnus

V Congreso de Biologia de la Conservacion de Plantas 28 sept. – 1 oct. 2011 - Es Mercadal (Menorca)

Alessandro Fisogni, Martina Rossi, Giovanni Cristofolini & Marta Galloni

Department of Experimental Evolutionary Biology, University of Bologna - Italy

Dictamnus albus L.

- Long-lived perennial herb (up to 30 years)

- Flowering: April-May

- Fruits: star-shaped capsules

- Dissemination: autochory

- Habitat: edges and clearings of warm mediterranean Oak woods (100-800 m a.s.l.)

- Chorotype: eurasiatic

Rare and threatened both in Europe and Asia

Italy: distribution limit

Locally protected (I; EU)

Study site

Land-use change

Suitable habitats fragmented and

surrounded by agricultural landscapes; canopy closure

SCI-SPA IT4050001 Natura 2000 Network

Phenology

Phase ♂: 3.20 ± 0.20 gg Phase ♀: 2.70 ± 0.75 gg

3 steps

1 step

- Dichogamy ?Peroxidase test

In vivo pollen tubes germination

- Peroxidase activity only on upward bending stigmas

- Lack of germinated pollen grains on downward bending stigmas

Heterodichogamy

Yes: protandry

- Herchogamy

Phenology

Asynchronous maturation of flowers on the raceme - from bottom to top

In vivo germination

All pollen tubes were longer than ¾ of - or as much as - the style

0

25

50

75

100

self control

% g

erm

inat

ion

treatment

n=15 n=13

Physiologicalself-incompatibility?

No

Open pollinated controls (C)

Breeding system

Agamospermy Stigma excision

Autogamy Spontaneous (SS)

Hand-pollinated (HS)

Reproductive success

Significant diff.: SS - HS (p=0.02); SS - C (p

♂♀

Nectar analysis

: open racemes: bagged racemes

- Nectar analysis along the raceme

- Comparison between bagged and unbagged racemes

- Higher uptake in older phases

- GBNP (♀ phase)

Fisogni et al. 2011

Visitors vs.

pollinators

- Floral reward

- Flowers visited per plant

- Contact with receptive stigma

: pollinators: visitors: no obs.

Fisogni et al. 2011

Insect nRelative

abundancePollen fidelity PI

Apis mellifera

8 0.13 0.94 0.12

Bombus spp. 11 0.19 0.68 0.13

Megachile sp.

7 0.11 0.72 0.08

Pollinator importance

PI = relative abundance x fidelity

Direct correlation between PI Max and fruit production

Fisogni et al. 2011Galloni et al. 2008

Pollinator directionality

1

3

5

2

4b ≥1 upward

b ≈ 0 random

b < 0 downward

DirectionLine slope

Flowers in different sexual phases at the same time on the raceme

Hp: Possible geitonogamy (b ≤ 0)

Insect n b Modified Student's t

p-value

Apis mellifera 36 1.41 ± 0.35

1.64 0.05

Bombus spp. 10 1.87 ± 0.53

2.35 0.02

Megachile sp. 19 0.24 ± 0.48

- 2.22 0.02

Pollinator directionality

Modified Student’s t = (b - 1) / SEb

- Bombus and Apis: upward visits

- Megachile: random visits

b = 1: threshold beyond which geitonogamy has minor effect

No geitonogamy

Geitonogamy (weak effect)Fisogni et al. 2011

Pollinator limitation

Hand pollen supplementation

: C

: S

2007 (t-test) - Fr:fl: t = 2.15, p = 0.04 S:O: t = 2.35, p = 0.032008 (t-test) - n.s. diff.

0,2

0,4

0,6

0,8

1,0

2007 2008

Fr:fl

Year

0,100

0,325

0,550

0,775

1,000

2007 2008

S:O

Year

* *

43129 60127

In 2008 more flowering plants

Demographic study

Permanent quadrats (3x3 m) – years: 2008-2010

2 ecological situations

Wood edge

Mature wood

Class ages

Seedlings (P)

Juveniles (P2)

Young – 3 leaflets (GT)

Adults – non flowered (A)

Adults – fruited (F)

Demographic study

0

12,5

25,0

37,5

50,0

P P2 GT A F

Margine 2008

Abb

onda

nza

rela

tiva

Classi di età

0,4

15,3

30,2

45,1

60,0

P P2 GT A F

Margine 2009

Abb

onda

nza

rela

tiva

Classi di età

Wood edge2008

2009

0

15

30

45

60

P P2 GT A F

Margine 2010

Abb

onda

nza

rela

tiva

Classi di età

2010

0

15

30

45

60

P P2 GT A F

Bosco maturo 2008

Abb

onda

nza

rela

tiva

Classi di età

0

12,5

25,0

37,5

50,0

P P2 GT A F

Bosco maturo 2009

Abb

onda

nza

rela

tiva

Classi di età

0

12,5

25,0

37,5

50,0

P P2 GT A F

Bosco maturo 2010

Abb

onda

nza

rela

tiva

Classi di età

2008

2009

2010

Mature wood

n=27

n=25

n=25

n=215

n=208

n=239

rela

tive

abun

danc

ere

lativ

e ab

unda

nce

rela

tive

abun

danc

e

class ages class ages