Selection imposed by pollination mode minimally influences evolution of pollen morphology in Thalictrum (Ranunculaceae)
Pollen morphological features such as grain size, grain shape, and number and arrangement of apertures influence the efficacy of the critical processes of pollination and fertilization. Optimal character states also vary with the environment experienced by the pollen grain.
As such, the conditions surrounding pollen transmission and germination may exert specific selective pressures on pollen morphology.
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We used the robust dataset of pollen-grain sizes and aperture numbers in Thalictrum (Humphrey 2016) and a well-resolved phylogeny of the genus Thalictrum (Soza, Haworth and Di Stilio 2013) to test whether evolution of pollen grain morphology is constrained by pollination mode.
Specifically, we examine the hypothesis that evolutionary shifts in pollen grain size and aperture number are correlated with transitions from insect to wind pollination systems.
Hypotheses about probable selective pressures associated with pollen grain transmission, longevity, germination, and competition within the style
