Abstract Detail



Sexual selection in flowering plants: traits, processes, and estimation

Mazer, Susan [2], Hendrickson, Brandon [1], Chellew, Joseph [2], Kim, Lynn [2], Liu, Jasen [2], Vasudevan, Manju [2].

Divergence in pollen tube growth rates between autogamous vs. outcrossing Clarkia sister species: is sexual selection relaxed in selfers?

In angiosperm populations, sexual selection among competing male gametophtyes may influence the evolution of pollen performance traits that are both heritable and associated with siring success. Traits such as the stigma penetrance rate (the proportion of pollen grains adhering to the stigma whose tubes penetrate the stigma within a given time period) and mean pollen tube growth rate (PTGR) are predicted to diverge between selfing and outcrossing sister taxa because stigmas of the latter receive a higher diversity of pollen genotypes, generating a greater opportunity for selection to favor male gametophytes that germinate rapidly and that produce fast-growing pollen tubes. Here we describe the first study designed to test this prediction in multiple populations under controlled conditions. Following hand-pollinations, we examined differences in pollen performance between two Clarkia sister species: the predominantly outcrossing C. unguiculata and the facultatively autogamous C. exilis. Within four populations of each species, groups of 5-8 individuals were reciprocally pollinated in a diallel design (a total of 1153 pollinations were assessed). Using pollen donor means, we examined the independent effects of species, population, self- vs. outcross pollen, the number of competing pollen grains per stigma, stigma penetrance rate, and temperature on pollen performance. C. unguiculata exhibited significantly higher mean PTGR than C. exilis. The two species exhibited similar levels of variation among pollen donors in both stigma penetrance rate and PTGR. The difference between C. unguiculata and C. exilis in PTGR is consistent with predictions of sexual selection theory. Several other observations, however, challenged theoretical predictions.


Related Links:
Divergence in pollen performance between Clarkia sister species with contrasting mating systems supports predictions of sexual selection. Evolution
http://https://onlinelibrary-wiley-com.proxy.library.ucsb.edu:9443/doi/full/10.1111/evo.13429


1 - University of California, Merced, School of Natural Sciences, Merced, CA, 95343, USA
2 - University of California, Santa Barbara, Ecology, Evolution & Marine Biology, Santa Barbara, CA, 93106, USA

Keywords:
Mating system evolution
Clarkia
Sexual selection
Pollen competition
Pollen tube growth rate
Gametophytic selection.

Presentation Type: Colloquium Presentations
Number: 0010
Abstract ID:140
Candidate for Awards:None


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