Abstract
We used 32 polymorphic microsatellite loci to investigate how a mixed-mating system affects population genetic structure in Central American populations (N = 243 individuals) of the killifish Kryptolebias marmoratus (mangrove rivulus), 1 of 2 of the world's only known self-fertilizing vertebrates. Results were also compared with previous microsatellite surveys of Floridian populations of this species. For several populations in Belize and Honduras, population structure and genetic differentiation were pronounced and higher than in Florida, even though the opposite trend was expected because populations in the latter region were presumably smaller and highly selfing. The deduced frequency of selfing (s) ranged from s = 0.39-0.99 across geographic locales in Central America. This heterogeneity in selfing rates was in stark contrast to Florida, where s > 0.9. The frequency of outcrossing in a population (t = 1 - s) was tenuously correlated with local frequencies of males, suggesting that males are one of many factors influencing outcrossing. Observed distributions of individual heterozygosity showed good agreement with expected distributions under an equilibrium mixed-mating model, indicating that rates of selfing remained relatively constant over many generations. Overall, our results demonstrate the profound consequences of a mixed-mating system for the genetic architecture of a hermaphroditic vertebrate.
Highlights
We used 32 polymorphic microsatellite loci to investigate how a mixed-mating system affects population genetic structure in Central American populations (N = 243 individuals) of the killifish Kryptolebias marmoratus, 1 of 2 of the world’s only known self-fertilizing vertebrates
For several populations in Belize and Honduras, population structure and genetic differentiation were pronounced and higher than in Florida, even though the opposite trend was expected because populations in the latter region were presumably smaller and highly selfing.The deduced frequency of selfing (s) ranged from s = 0.39–0.99 across geographic locales in Central America.This heterogeneity in selfing rates was in stark contrast to Florida, where s > 0.9.The frequency of outcrossing in a population (t = 1 − s) was tenuously correlated with local frequencies of males, suggesting that males are one of many factors influencing outcrossing
We used 32 microsatellite loci developed for K. marmoratus (Mackiewicz et al 2006a), which were amplified in several multiplex reactions, as described previously (Tatarenkov et al 2012)
Summary
We used 32 polymorphic microsatellite loci to investigate how a mixed-mating system affects population genetic structure in Central American populations (N = 243 individuals) of the killifish Kryptolebias marmoratus (mangrove rivulus), 1 of 2 of the world’s only known self-fertilizing vertebrates. Because the impact of genetic drift is higher with smaller Ne, population structure should be magnified by inbreeding (Maruyama and Tachida 1992; Charlesworth and Pannell 2001), as has been demonstrated in several species of selfing plants and animals (Hamrick and Godt 1996; Jarne 1995; Jarne and Auld 2006). Whereas genetic variation in local populations is expected to be low in selfing species, genetic diversity over the entire species’ range may be exceptionally high due to pronounced population subdivision that conserves distinct genetic variants (Charlesworth and Pannell 2001; Ingvarsson 2002). There is currently no satisfactory explanation why males comprise about 20% of the Twin Cays population, while other locations in Belize and Honduras reportedly have male frequencies as low as 1–2%, similar to those observed in Florida and the Bahamas (Taylor et al 2001; Turner et al 2006; Ellison et al 2012)
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