Discordant Distribution of Populations and Genetic Variation in a Sea Star With High Dispersal Potential

Abstract

Patiria miniata, a broadcast-spawning sea star species with high dispersal potential, has a geographic range in the intertidal zone of the northeast Pacific Ocean from Alaska to California that is characterized by a large range gap in Washington andOregon. We analyzed spatial genetic variation across the P. miniata range using multilocus sequence data (mtDNA, nuclear introns) and multilocus genotype data (microsatellites). We found a strong phylogeographic break at Queen Charlotte Sound in British Columbia that was not in the location predicted by the geographical distribution of the populations. However, this population genetic discontinuity does correspond to previously described phylogeographic breaks in other species. Northern populations from Alaska and Haida Gwaii were strongly differentiated from all southern populations from Vancouver Island and California. Explaining the origin and persistence of large geographical discontinuities in species distributions, such as the antitropical distributions of many temperate-zone animals and plants, is one of the original goals of evolutionary ecology (Darwin 1859;Ekman 1953;Briggs 1987;Wiley 1988;Lindberg 1991). Such range disjunctions may be initiated and maintained by a complex combination of factors, encompassing extrinsic geological and climatic barriers to dispersal and colonization, and intrinsic biological properties of organisms including habitat preferences 4 Current address: Populations from Vancouver

Extraordinarily rapid life-history divergence between Cryptasterina sea star species

“…C. pentagona has relatively modest levels of genetic diversity when compared with other asterinid sea stars with planktonic development [32,50]; however, C. hystera shows a dramatic reduction in nucleotide diversity, allelic diversity and most notably heterozygosity (see electronic supplementary material, table S1). Only one microsatellite locus is polymorphic across the entire known range of this species, and this locus is completely fixed within populations.…”

“…DNA extraction, PCR amplification, sequencing and genotyping all followed the protocols in Keever et al [32,33]. All individuals were genotyped at five microsatellite loci (including three shared between species): a108, b202, b227, b231 and c219 were used in C. pentagona; loci a102, b202, b227, c219 and d8 were used for C. hystera.…”

Coastal pollution limits pelagic larval dispersal

“…In these situations, the only evolutionary force acting on allele frequencies in these populations will be genetic drift, which has larger effects on smaller effective population sizes 38 , and has been shown to be rampant in artificially fragmented populations 39 . Therefore, considering the high genetic diversity of P. miniata and previous connectivity 17 , we would expect to see a more pronounced signal of anthropogenic isolation in the mtDNA markers, which have an effective population ~1/4 the size of the nDNA markers 38 . In all population structure models tested, we observed that R 2 values were ~1.5-30 times higher for mtDNA markers relative to nDNA markers (Tables 2-4), although results from nDNA genetic diversity regressions were consistent with anthropogenic isolation (Fig.…”

“…17 with the exception of using dye-labelled primers and an ABI 3730XL for genotyping. Two mtDNA loci were sequenced, a tRNA region and part of the cytochrome oxidase subunit I gene (COI) 17 and control region (CR) 42 . The two mtDNA loci were analysed as a LD marker (COI) and as a full mtDNA marker (COI + CR).…”

“…P. miniata is a ubiquitous omnivore found along the subtidal and intertidal west coast of North America. It has a 6-10-week pelagic larval development period, a potential yearround breeding season that may peak in summer 15,16 , and has been shown to have both high genetic diversity and high genetic connectivity between populations over 1,000-km apart 17 . Moreover, P. miniata is a non-fished, non-harvested species relatively free from any direct human impact, making it a conservative system to test for human-mediated effects on connectivity.…”