Flower: a specialized shoot with 4 whorls of modified leaves

sepals (calyx)

petals (corolla)

stamen (filament + anther)

pistil (stigma + style + ovary)

sterile

Dimorphic gender expression

the presence of two sexual

mating types in populations

Cosexual gender expression

combine both gender functions

within individuals

Monomorphic

the presence of a single sexual

mating type in a population

H

ca. 10% of all

angiosperm species

F

M

H

F

M

H

M

F

H

H

F

M

F

M

F

M

F H

Male-sterility

mutation

Female-sterility

mutation

•! Modular construction & the “packaging” of gender

•! Dependent on vectors for pollen dispersal

•! Rooted to the ground

•! Lack sophisticated sensory abilities, behaviors

Challenges & complications…

•!Cosexual gender expression & the potential for

self-fertilization

Finding potential mates

•! Use wind/water to move pollen

•! Not very efficient

•! Floral specialization

Abiotic pollination

Finding potential mates

•! Exploit sensory systems of animals

•! Floral specialization

•! Pollination “syndromes”

Biotic pollination

Visual cues (color, nectar guides)

Morphology (symmetry, tubes)

Olfactory

Mimicry (sexual, resource)

Rewards (pollen, nectar)

Stensmyr et al. Nature (2002)

Arum volatiles

Identified active odor compounds

in Arum inflorescences…

Characterized the response of

flies to odor of Arum flowers…

Stensmyr et al. Nature (2002)

Arum volatiles

carrion volatiles Same active odor compounds in

Arum inflorescences and carrion

Stensmyr et al. Nature (2002)

Arum volatiles

carrion volatiles Same active odor compounds in

Arum inflorescences and carrion

Blowfly antennae responded

identically to sulphide odors from

carrion and Arum

Finding potential mates

•! Facilitate finding mates”

Pollination syndromes

OR

Self pollination/fertilization

The evolution of selfing is perhaps the most common transition in angiosperm evolution

world famous selfer, Arabidopsis thaliana

Self-fertilization

within a flower

among flowers

on the same plant

Self-fertilization seems like a good idea

•! Isolated individuals

•! Plants at the edge of a species range

•! In years with poor pollinator service

•! Locally adapted populations Anthoxanthum odoratum (Poaceae)

Ability to self-fertilize

reasonable under some circumstances

Self-fertilization seems like a good idea

reasonable under some circumstances

inbreeding depression often a problem

, but…

IBD in white clover (Trifolium repens)

Outcrossed plants Selfed plants

•! Isolated individuals

•! Plants at the edge of a species range

•! In years with poor pollinator service

•! Locally adapted populations

Flowers do not open;

obligate selfers (e.g., violets)

Some groups tolerate self-fertilization…

and seemingly have adaptations to promote it!

or evolved as a consequence of it (selfing)

Amsinckia spp. (Boraginaceae)

Some lineages of plants

tolerate self-fertilization

outcrosser selfer

Eichhornia crassipes

(Pontederiaceae)

Flowers from selfing populations are

smaller than those in outcrossing pop’lns

outcrossing selfing

Plants from selfing populations make fewer

flowers than those in outcrossing pop’lns

Outcross >200 vs. Selfed <100

(A) Brazil - outbreeding population

5 generations of self-fertilization

5 generations of self-fertilization

Significant

IBD

No

significant

IBD

(B) Jamaica - selfing (inbred) population)

Some lineages of plants

tolerate self-fertilization

Prediction for inbreeding depression?