Range‐wide genetic homogeneity in the California sea mussel (Mytilus californianus): a comparison of allozymes, nuclear DNA markers, and mitochondrial DNA sequences

Abstract

We tested for genetic differentiation among six populations of California sea mussels (Mytilus californianus) sampled across 4000 km of its geographical range by comparing patterns of variation at four independent types of genetic markers: allozymes, single-copy nuclear DNA markers, and DNA sequences from the male and female mitochondrial genomes. Despite our extensive sampling and genotyping efforts, we detected no significant differences among localities and no signal of isolation by distance suggesting that M. californianus is genetically homogeneous throughout its range. This concordance differs from similar studies on other mytilids, especially in the role of postsettlement selection generating differences between exposed coastal and estuarine habitats. To assess if this homogeneity was due to M. californianus not inhabiting estuarine environments, we reviewed studies comparing allozymes with other classes of nuclear DNA markers. Although both types of markers gave broadly consistent results, there was a bias favouring studies in which allozymes were more divergent than DNA markers (nine to three) and a disproportionate number of these cases involved marine taxa (seven). Furthermore, allozymes were significantly more heterogeneous than DNA markers in three of the four studies that sampled coastal and estuarine habitats. We conclude that the genetic uniformity exhibited by M. californianus may result from a combination of extensive gene flow and the lack of exposure to strong selective gradients across its range.

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

“…Most notably, neither microsatellite (Fenberg et al 2010) nor mitochondrial (Dawson 2001;P. B. Fenberg, unpublished data) markers provide evidence of significant genetic differentiation among the populations sampled here; a pattern commonly observed for broadcast spawning marine invertebrates along the California coast (e.g., Dawson 2001;Gruenthal et al 2007;Addison et al 2008). Second, although our study ranges across 3.9Њ of latitude, the three protected populations are evenly spread across this area and in the case of the Cabrillo National Monument, within 20 km from the nearest sampled exploited site ( fig.…”

Genetic characterization and evaluation of anthropogenic impacts on genetic patterns in cultured and wild populations of mussels (Mytilus galloprovincialis) from Greece

“…Such results are common in Mytilus species and have been reported in a number of studies, including those for populations of M. chilensis along Chilean coasts using RAPD markers (Toro et al, 2004) and for M. californianus from Californian coasts using allozyme, mtDNA, and single-copy nuclear DNA markers (Addison et al, 2008).…”

“…Several types of genetic markers have been frequently applied in population genetic studies of aquatic organisms. In mussels of the genus Mytilus, previous studies dealt with species and hybrid identification (Beaumont et al, 2008) and with their population structure in Western Europe (Daguin and Borsa, 1999) and America (Addison et al, 2008). However, despite its utility for aquaculture purposes, few reports have been published regarding the population genetic structure of M. galloprovincialis along the Greek and Turkish coastlines.…”

The environmentally tuned transcriptomes ofMytilusmussels

“…However, it is pertinent to also study earlier larval and juvenile stages. In particular, as a result of the long pelagic larval durations (Strathmann, 1985) and great distances that larvae and juveniles are transported (Addison et al, 2008), pre-and post- Genes that exhibited statistically significant changes in genes expression in response to heat in the datasets of Lockwood et al (2010) and Connor and Gracey (2011) were ranked according to the sum of their ranks of statistical significance in both datasets, with the most significantly induced genes being positioned at the top of the heatmap. Up-regulated common response genes are shown first followed by the common response down-regulated genes.…”