Shallow gene pools in the high intertidal: extreme loss of genetic diversity in viviparous sea stars ( Parvulastra )

Abstract

We document an extreme example of reproductive trait evolution that affects population genetic structure in sister species of Parvulastra cushion stars from Australia. Self-fertilization by hermaphroditic adults and brood protection of benthic larvae causes strong inbreeding and range-wide genetic poverty. Most samples were fixed for a single allele at nearly all nuclear loci; heterozygotes were extremely rare (0.18%); mitochondrial DNA sequences were more variable, but few populations shared haplotypes in common. Isolation-with-migration models suggest that these patterns are caused by population bottlenecks (relative to ancestral population size) and low gene flow. Loss of genetic diversity and low potential for dispersal between high-intertidal habitats may have dire consequences for extinction risk and potential for future adaptive evolution in response to climate and other selective agents.

Low genetic diversity and recent demographic expansion in the red starfish Echinaster sepositus (Retzius 1816)

“…There are no previous studies of echinoderms with lecitothrophic larvae using the same genetic markers and geographical area available for comparison, but the haplotype diversity found for COI data was comparable to that of some other benthic groups, such as some colonial ascidians and molluscs, with very limited dispersal potential 9 60 . Low allelic richness has been explained in other marine species as a result of high levels of inbreeding and/or population decline 61 62 . Nevertheless, for E. sepositus , we did not detect signs of current inbreeding across the whole distribution range, although we did in a few subpopulations, and there was no evidence of recent bottlenecks.…”

Incipient Speciation of Sea Star Populations by Adaptive Gamete Recognition Coevolution

“…We used isolation‐with‐migration models of population demographic history to characterize patterns of gene flow between northern and southern populations using each of those four datasets A through D. We used data from our analyses of egg‐expressed genes and our previously published bindin data. We treated partitions as loci and carried out multilocus analyses in IMa (Hey and Nielsen ; e.g., see Puritz et al ; Keever et al ). We used all partitions of all genes except Rendezvin (Table S1): for this gene, we were unable to infer all recombination sites simultaneously in one analysis; instead, we divided the Rendezvin alignment into three subalignments (with similar numbers of repetitive protein‐coding domains), analyzed each of those subalignments for recombination, and included the longest partition from each as three loci in the IMa dataset.…”

Intraspecific genetic structure, divergence and high rates of clonality in an amphi‐Atlantic starfish

“…The existence of repeated identical multilocus genotypes (MLGs) is a recognizable sign of clonal reproduction, although no exclusive of asexuality. High levels of inbreeding can also generate patterns of low genetic diversity, fixation of alleles and repeated MLGs (Keever et al., ; Puritz et al., ). Other genetic signs, together with the presence of repeated identical MLGs, can be assessed when long‐term clonal reproduction is prevalent in populations, and allow high rates of clonality to be distinguished from inbreeding (Balloux, Lehmann, & De Meeûs, ; de Meeûs et al., ).…”