Pleistocene separation of mitochondrial lineages of Mytilus spp. mussels from Northern and Southern Hemispheres and strong genetic differentiation among southern populations

Abstract

Smooth-shelled mussels, Mytilus spp., have an antitropical distribution. In the Northern Hemisphere, the M. edulis complex of species is composed of three genetically well delineated taxa: M. edulis, M. galloprovincialis and M. trossulus. In the Southern Hemisphere, morphological characters, allozymes and intron length polymorphisms suggest that Mytilus spp. populations from South America and Kerguelen Islands are related to M. edulis and those from Australasia to M. galloprovincialis. On the other hand, a phylogeny of the 16S rDNA mitochondrial locus demonstrates a clear distinctiveness of southern mussels and suggests that they are related to Mediterranean M. galloprovincialis. Here, we analysed the faster-evolving cytochrome oxidase subunit I locus. The divergence between haplotypes of populations from the two hemispheres was confirmed and was found to predate the divergence between haplotypes of northern M. edulis and M. galloprovincialis. In addition, strong genetic structure was detected among the southern samples, revealing three genetic entities that correspond to (1) South America and Kerguelen Island, (2) Tasmania, (3) New Zealand. Using the trans-Arctic interchange as a molecular clock calibration, we estimated the time since divergence of populations from the two hemispheres to be between 0.5 million years (MY) and 1.3 MY (average 0.84 MY). The contrasting patterns observed for the nuclear and the organelle genomes suggested two alternative, complex scenarios: two trans-equatorial migrations and the existence of differential barriers to mitochondrial and nuclear gene flow, or a single trans-equatorial migration and a view of the composition of the nuclear genome biased by taxonomic preconception.

Adaptive genetic variation distinguishes Chilean blue mussels (Mytilus chilensis) from different marine environments

“…2008). Like many marine invertebrates, mussel larvae have a planktonic lifetime of weeks or months, and thereby can be potentially dispersed over large geographical areas by marine currents or human‐mediated activities (Hilbish et al.…”

Genetic composition of Mytilus species in mussel populations from southern Chile

“…Biochemical and molecular characterization divided the morphologically classified Mytilus edulis Linnaeus, 1758 into a complex of three sibling species termed the Mytilus edulis species complex: M. edulis, M. trossulus Gould, 1850 and M. galloprovincialis Lamarck, 1819 (Westfall & Gardner, 2010). The genetic composition of these three taxa, now globally well defined, in the northern hemisphere (Wonham, 2004;Gérard et al, 2008); in contrast, in southern hemisphere the composition is still under analysis.…”

Genetic Diversity and Evolution of Marine Animals Isolated in Marine Lakes

“…Evolutionary aspects of marine lake mussels Genetic diversity of the marine lake mussels, inferred from the haplotype diversity (h = 0.000-0.662) and nucleotide diversity (π = 0.000-0.002), tended to be lower than that reported for other mussels inhabiting seashores, such as Floridian Brachidontes (h = 0.546-0.987) Foighil, 2004, 2005), Mediterranean Brachidontes (h = 0.733-1.000; π = 0.005-0.042) (Terranova et al, 2006(Terranova et al, , 2007 and Mytilus collected from the northern and southern hemispheres (h = 0.600-0.950; π = 0.002-0.021) (Gérard et al, 2008). This indicates a small effective population size and/or past bottlenecking of the marine lake populations.…”

“…The genetic distance between ON-and MC-morphs (average p-distance at the third codon position = 0.0053; 0.022-0.029 million years ago) was as small as the level within a species or among closely related taxa in the M. edulis species complex (Gérard et al, 2008). This may indicate that a rapid change can occur in shell morphology of mussels in the marine lakes.…”