Discriminating between the effects of founding events and reproductive mode on the genetic structure of Triops populations (Branchiopoda: Notostraca)

PLoS One. 2014 May 13;9(5):e97473. doi: 10.1371/journal.pone.0097473. eCollection 2014.

Abstract

Crustaceans that initially colonize a freshwater temporary pond can strongly bias the subsequent genetic composition of the population, causing nearby populations to be genetically distinct. In addition, these crustaceans have various reproductive modes that can influence genetic differentiation and diversity within and between populations. We report on two species of tadpole shrimp, Triops newberryi and Triops longicaudatus "short", with different reproductive modes. Reproduction in the tadpole shrimp can occur clonally (parthenogenesis), with self fertilization (hermaphroditism), or through outcrossing of hermaphrodites with males (androdioecy). For all these reproductive modes, population genetic theory predicts decreased genetic diversity and increased population differentiation. Here we use mitochondrial control region (mtCR) sequences and nuclear microsatellite loci to determine if the difference in reproductive mode affects the high genetic structure typical of persistent founder effects. Previous authors indicated that T. newberryi is androdioecious because populations are composed of hermaphrodites and males, and T. longicaudatus "short" is hermaphroditic or parthenogenetic because males are absent. In our data, T. newberryi and T. longicaudatus "short" populations were highly structured genetically over short geographic distances for mtCR sequences and microsatellite loci (T. newberryi: ΦST = 0.644, FST = 0.252, respectively; T. l. "short": invariant mtCR sequences, FST = 0.600). Differences between the two Triops species in a number of diversity measures were generally consistent with expectations from population genetic theory regarding reproductive mode; however, three of four comparisons were not statistically significant. We conclude the high genetic differentiation between populations is likely due to founder effects and results suggest both species are composed of selfing hermaphrodites with some level of outcrossing; the presence of males in T. newberryi does not appreciably reduce inbreeding. We cannot exclude the possibility that males in T. newberryi are non-reproductive individuals and the two species have the same mating system.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • DNA, Mitochondrial / genetics
  • Decapoda / genetics*
  • Founder Effect*
  • Genetic Variation*
  • Genetics, Population*
  • Locus Control Region / genetics
  • Microsatellite Repeats / genetics
  • Molecular Sequence Data
  • Reproduction / genetics*
  • Sequence Analysis, DNA
  • Species Specificity

Substances

  • DNA, Mitochondrial

Grants and funding

The research was supported by the New Mexico Agricultural Experiment Station and by support to DEC from the Cooperative State Research, Education and Extension Service, US Department of Agriculture under Agreement numbers 2008-34461-19061 and 2008-40549-04328 in cooperation with New Mexico State University and the Texas A & M University System. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.