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Abstract Detail

Speciation Mechanisms in Plants

Moeller, David [1].

Reinforcement and ecological speciation between incipient outcrossing and selfing Clarkia species.

Studies of reproductive isolation often find that prezygotic barriers evolve more rapidly than postzygotic barriers between incipient species. However, it has been challenging to determine whether selection has directly resulted in elevated assortative mating (reinforcement) or whether reproductive isolation has occurred as a by-product of adaptation to alternative environments. In Clarkia xantiana, there is a pronounced pattern of reproductive character displacement (RCD) between incipient plant species that remain cross-compatible, a key signature of reinforcement. Mating is mediated by interactions with specialized bee pollinators whose population dynamics and evolution are linked to that of Clarkia populations. Here, we test whether reinforcement selection has directly caused the evolution of RCD in quantitative floral traits using a series of field experiments. In particular, we examined whether assortative mating was stronger between sympatric populations than allopatric populations. Our results show that assortative mating is very high between sympatric genotypes resulting in few hybrids. Whereas, assortative mating is weaker between allopatric genotypes and hybridization is approximately twice as likely, consistent with the reinforcement hypothesis. Pollinator discrimination largely determines the likelihood of hybridization. We also tested the alternative hypothesis that RCD developed as by-product of adaptation to contrasting pollination environments in the allopatric and sympatric regions. However, we found no evidence for this hypothesis. Overall, these results emphasize an important contribution of mating system divergence to the speciation process in plants.

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1 - Department Of Plant And Microbial Biology, 1479 Gortner Avenue, St. Paul, MN, 55108, United States

Reproductive Isolation
mating system
character displacement
outcrossing and selfing
floral evolution
assortative mating

Presentation Type: Colloquium Presentations
Session: C09, Speciation Mechanisms in Plants
Location: /
Date: Thursday, July 22nd, 2021
Time: 1:30 PM(EDT)
Number: C09004
Abstract ID:133
Candidate for Awards:None

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