Conservation genetics of the alligator snapping turtle: cytonuclear evidence of range-wide bottleneck effects and unusually pronounced geographic structure

Abstract

A previous mtDNA study indicated that femalemediated gene flow was extremely rare among alligator snapping turtle populations in different drainages of the Gulf of Mexico. In this study, we used variation at seven microsatellite DNA loci to assess the possibility of malemediated gene flow, we augmented the mtDNA survey with additional sampling of the large Mississippi River System, and we evaluated the hypothesis that the consistently low within-population mtDNA diversity reflects past population bottlenecks. The results show that dispersal between drainages of the Gulf of Mexico is rare (F STmsat = 0.43, U STmtDNA = 0.98). Past range-wide bottlenecks are indicated by several genetic signals, including low diversity for microsatellites (1.1-3.9 alleles/locus; H e = 0.06-0.53) and mtDNA (h = 0.00 for most drainages; p = 0.000-0.001). Microsatellite data reinforce the conclusion from mtDNA that the Suwannee River population might eventually be recognized as a distinct taxonomic unit. It was the only population showing fixation or near fixation for otherwise rare microsatellite alleles. Six evolutionarily significant units are recommended on the basis of reciprocal mtDNA monophyly and high levels of microsatellite DNA divergence.

Cryptic Population Structuring and the Role of the Isthmus of Tehuantepec as a Gene Flow Barrier in the Critically Endangered Central American River Turtle

“…This turtle also has a high commercial value, and is distributed in different drainages of the Gulf of Mexico in the USA, but shows very low levels of gene flow for both microsatellites and mtDNA markers [73]. In our analysis, D. mawii individuals were frequently assigned to localities far away from their collection sites.…”

Multilocus evidence for globally distributed cryptic species and distinct populations across ocean gyres in a mesopelagic copepod

“…Weaker population genetic structure at nuclear microsatellite markers than mtDNA has also been commonly observed across a wide variety of other marine organisms (e.g. marine fish, Shaw et al 2004;DiBattista et al 2012; freshwater and marine turtles, Bowen et al 2005;Echelle et al 2010;sea snakes, Lukoschek et al 2008;marine mammals, Lyrholm et al 1999;Andrews et al 2010; but for counter examples, see Eble et al 2011;Muths et al 2011). Several explanations have been invoked to account for this discrepancy between marker types, including the greater susceptibility of mtDNA markers to drift than nuclear markers due to their haploid, uniparental inheritance (Birky et al 1983;Wilson et al 1985;Avise 2004); higher mutation rates for microsatellites, which can deflate F ST (Hedrick 1999;Balloux et al 2000;Buonaccorsi et al 2001;O'Reilly et al 2004); increased homoplasy for microsatellites (Estoup et al 2002); male-biased dispersal (e.g.…”

Evaluating the Significance of Paleophylogeographic Species Distribution Models in Reconstructing Quaternary Range-Shifts of Nearctic Chelonians

“…Genetic data reveal strong population bottlenecks for various turtle and tortoise species from the southern US and Mexico [104], [123]–[124], except for species where different refugial ranges became evident during modeling (e.g. [104], [106], [125], but see [126]). For example, SDMs obtained for Emydoidea blandingii , Glyptemys insculpta and Glyptemys muhlenbergii highlight strongly restricted and small refugia over a long time period and,molecular analyses reveal a negative impact on intraspecific diversity.…”