Scorched mussels (BIVALVIA: MYTILIDAE: BRACHIDONTINAE) from the temperate coasts of South America: Phylogenetic relationships, trans-Pacific connections and the footprints of Quaternary glaciations

TROVANT, B.; ORENZANZ, J.M.; RUZZANTE, D.E.; STOTZ, W; BASSO, N. G.

MOLECULAR PHYLOGENETICS AND EVOLUTION

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2015 vol. 82 p. 60 - 74

1055-7903

This study addresses aspects of the phylogeny and phylogeography of scorched mussels (BIVALVIA:MYTILIDAE: BRACHIDONTINAE) from southern South America (Argentina and Chile), as well as theirecophylogenetic implications. Relationships were inferred from sequences of two nuclear (28S and18S) and one mitochondrial (COI) genes, using Bayesian and maximum likelihood analyses. Our resultsindicate that the monophyletic BRACHIDONTINAE include three well supported clades: [i] BrachidontesSwainson (=Hormomya Morch), [ii] Ischadium Jukes-Browne + Geukensia van de Poel, and [iii] AustromytilusLaseron + Mytilisepta Habe (usually considered a member of the SEPTIFERINAE) + Perumytilus Olsson.Species of clade [iii] are distributed along the temperate coasts of the Pacific Ocean. Available evidencesupports divergence between Austromytilus (Australia) and Perumytilus (South American) following thebreakup of Australian, Antarctic and South American shelves. Four brachidontins occur in southern SouthAmerica: Brachidontes rodriguezii (d?Orbigny), B. granulatus (Hanley), and two genetically distinct cladesof Perumytilus. The latter are confined to the Chile-Peru (North Clade) and Magellanic (South Clade) BiogeographicProvinces, respectively warm- and cold-temperate. The South Clade is the only brachidontinrestricted to cold-temperate waters. Biogeographic considerations and the fossil record prompted thehypothesis that the South Clade originated from the North Clade by incipient peripatric differentiation,followed by isolation during the Quaternary glaciations, genetic differentiation in the non-glaciatedcoasts of eastern Patagonia, back-expansion over southern Chile following post-LGM de-glaciation, anddevelopment of a secondary contact zone between the two clades in south-central Chile. Evidence ofupper Pleistocene expansion of the South Clade parallels similar results on other organisms that have colonizedcoastal ecosystems from eastern Patagonia since the LGM, apparently occupying free ecologicalspace. We emphasize that the assembly of communities cannot be explained solely in terms of environmentaldrivers, as history also matters.