Download Flower: a specialized shoot with 4 whorls of modified leaves sepals

Flower: a specialized shoot with 4 whorls of modified leaves
sepals (calyx)
sterile
petals (corolla)
stamen (filament + anther)
pistil (stigma + style + ovary)
H
F
Dimorphic gender expression
M
the presence of two sexual
mating types in populations
M
ca. 10% of all
angiosperm species
Cosexual gender expression
H
H
F
F
H
M
combine both gender functions
within individuals
Monomorphic
the presence of a single sexual
mating type in a population
F
M
H
H
F
F
Male-sterility
mutation
F
M
Female-sterility
mutation
M
Challenges & complications…
•! Lack sophisticated sensory abilities, behaviors
•! Rooted to the ground
•! Dependent on vectors for pollen dispersal
•! Modular construction & the “packaging” of gender
•! Cosexual gender expression & the potential for
self-fertilization
Finding potential mates
Biotic pollination
•! Exploit sensory systems of animals
Visual cues (color, nectar guides)
Morphology (symmetry, tubes)
Olfactory
Mimicry (sexual, resource)
Rewards (pollen, nectar)
•! Floral specialization
•! Pollination “syndromes”
Finding potential mates
Abiotic pollination
•! Use wind/water to move pollen
•! Not very efficient
•! Floral specialization
Arum volatiles
Arum volatiles
Identified active odor compounds
in Arum inflorescences…
carrion volatiles
Characterized the response of
flies to odor of Arum flowers…
Stensmyr et al. Nature (2002)
Stensmyr et al. Nature (2002)
Same active odor compounds in
Arum inflorescences and carrion
Finding potential mates
Arum volatiles
Pollination syndromes
carrion volatiles
Same active odor compounds in
Arum inflorescences and carrion
Blowfly antennae responded
identically to sulphide odors from
carrion and Arum
•! Facilitate finding mates”
OR
Self pollination/fertilization
world famous selfer, Arabidopsis thaliana
The evolution of selfing is perhaps the most
common transition in angiosperm evolution
Stensmyr et al. Nature (2002)
Self-fertilization
among flowers
on the same plant
Self-fertilization seems like a good idea
reasonable under some circumstances
•! Isolated individuals
•! Plants at the edge of a species range
•! In years with poor pollinator service
•! Locally adapted populations
within a flower
Anthoxanthum odoratum (Poaceae)
Ability to self-fertilize
Self-fertilization seems like a good idea , but…
inbreeding depression often a problem
Some groups tolerate self-fertilization…
and seemingly have adaptations to promote it!
reasonable under some circumstances
•! Isolated individuals
•! Plants at the edge of a species range
•! In years with poor pollinator service
•! Locally adapted populations
or evolved as a consequence of it (selfing)
Outcrossed plants
Selfed plants
Flowers do not open;
obligate selfers
(e.g., violets)
IBD in white clover (Trifolium repens)
Some lineages of plants
tolerate self-fertilization
Eichhornia crassipes
(Pontederiaceae)
outcrossing
Some lineages of plants
tolerate self-fertilization
selfing
(A) Brazil - outbreeding population
Amsinckia spp. (Boraginaceae)
5 generations of
self-fertilization
Significant
IBD
Flowers from selfing populations are
smaller than those in outcrossing pop’lns
Plants from selfing populations make fewer
flowers than those in outcrossing pop’lns
Outcross >200 vs. Selfed <100
outcrosser
selfer
Prediction for inbreeding depression?
(B) Jamaica - selfing (inbred) population)
5 generations of
self-fertilization
No
significant
IBD