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Consequences of multiple mating‐system shifts for population and range‐wide genetic structure in a coastal dune plant
Author(s) -
LópezVillalobos A.,
Eckert C. G.
Publication year - 2018
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.14484
Subject(s) - selfing , biology , outcrossing , mating system , population , evolutionary biology , genetic diversity , range (aeronautics) , mating , isolation by distance , gene flow , genetic variation , ecology , genetics , pollen , gene , materials science , demography , sociology , composite material
Abstract Evolutionary transitions from outcrossing to selfing can strongly affect the genetic diversity and structure of species at multiple spatial scales. We investigated the genetic consequences of mating‐system shifts in the North American, Pacific coast dune endemic plant Camissoniopsis cheiranthifolia (Onagraceae) by assaying variation at 13 nuclear (n) and six chloroplast (cp) microsatellite ( SSR ) loci for 38 populations across the species range. As predicted from the expected reduction in effective population size ( N e ) caused by selfing, small‐flowered, predominantly selfing ( SF ) populations had much lower nSSR diversity (but not cp SSR ) than large‐flowered, predominantly outcrossing ( LF ) populations. The reduction in nSSR diversity was greater than expected from the effects of selfing on N e alone, but could not be accounted for by indirect effects of selfing on population density. Although selfing should reduce gene flow, SF populations were not more genetically differentiated than LF populations. We detected five clusters of nSSR genotypes and three groups of cp SSR haplotypes across the species range consisting of parapatric groups of populations that usually (but not always) differed in mating system, suggesting that selfing may often initiate ecogeographic isolation. However, lineage‐wide genetic variation was not lower for selfing clusters, failing to support the hypothesis that selection for reproductive assurance spurred the evolution of selfing in this species. Within three populations where LF and SF plants coexist, we detected genetic differentiation among diverged floral phenotypes suggesting that reproductive isolation (probably postzygotic) may help maintain the striking mating‐system differentiation observed across the range of this species.