Genetic Subdivision and Variation in Selfing Rates Among Central American Populations of the Mangrove Rivulus, Kryptolebias marmoratus

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.

Diversity, distribution, and significance of transposable elements in the genome of the only selfing hermaphroditic vertebrate Kryptolebias marmoratus

“…Second, males are typically the result of hermaphrodites that transform into secondary males by ovarian atresia11. Most of the males in natural populations of this kind have been found to have transformed into an early life stage thereby ovarian tissue is typically absent at later life512131415. High levels of inbreeding like those observed in K. marmoratus are considered as maladaptive for a number of reasons like for example susceptibility to diseases1617.…”

Local parasite pressures and host genotype modulate epigenetic diversity in a mixed‐mating fish

“…We found that the different selfing lineages of Kryptolebias hermaphroditus distributed in three sampling sites of northeastern Brazil differed significantly in parasite loads, genetic composition, and DNA methylation patterns, which might indicate specific interactions between host genotypes, epigenotypes, and parasites (Dybdhal & Lively, ; Ebert, ). Previous studies on mangrove killifishes had identified extensive genetic structuring both between (Tatarenkov et al, , ) and within mangrove systems even at close geographical proximity (Ellison et al, ; Tatarenkov, Earley, Taylor, & Avise, ; Tatarenkov et al, ), as a consequence of the self‐fertilizing nature of these fish. We found strong evidence of genetic structuring between sampling sites and selfing lineages using microsatellites, but lower differentiation for AFLP genetic markers (likely due to the different mutation rate of the markers) and epigenetic markers (MS‐AFLPs).…”

Population genetics and evolution of the mangrove rivulus Kryptolebias marmoratus, the world's only self‐fertilizing hermaphroditic vertebrate

“…Two recent studies involving microsatellite loci have documented several of these effects for regional assemblages of K . marmoratus populations from the Florida Keys (Tatarenkov et al ., ) and for several sites in Central America (Tatarenkov et al ., ). In both cases, geographic population‐genetic structure was highly statistically significant and arranged in patterns that were marginally consistent with models of isolation by distance.…”

“…Observed distributions of individual heterozygosities in Central America also showed very good agreement with the distributions expected under an equilibrium mixed‐mating model with the same selfing rates (Fig. ) (Tatarenkov et al ., ). This latter finding suggests that despite pronounced spatial heterogeneity in genotypic frequencies, selfing rates within populations may tend to be rather stable through time.…”

“…Histogram showing the frequency distribution of individual heterozygosities in one Belizean population ( n = 59) of Kryptolebias marmoratus (after Tatarenkov et al , ). The x ‐axis shows the observed number of heterozygous loci (among 32 surveyed) in each individual.…”