Marine surf to freshwater: a molecular phylogeny of Donacidae (Bivalvia: Heterodonta)

Abstract

Donacidae is a commercially important family of heterodont bivalves and one of the few bivalve lineages that has successfully colonised brackish and fresh waters. However, to date, no phylogenetic hypothesis exists for this widely distributed group. Here we turn to molecular data from the nuclear and mitochondrial genomes and combine these with the extensive fossil record of donacids to propose an evolutionary hypothesis for the family. Our analyses strongly support the monophyly of Donacidae, including Galatea, Iphigenia and ‘Plebidonax’ deltoides, but render Donax paraphyletic. The subgenus Latona is therefore elevated to genus to accommodate a clade of Indo-Pacific species, while retaining Donax for a clade of mostly Atlantic and American Pacific species, and a few Indo-Pacific species. This latter clade is sister group to Galatea + Iphigenia. The diversification of Donacidae seems to be tightly connected to the opening of the North and South Atlantic Oceans in the Cretaceous, and to the closing of the Tethys Ocean during the Oligocene. Taxonomic actions: Latona columbella (Lamarck, 1818) comb. nov., L. deltoides (Lamarck, 1818) comb. nov., L. dysoni (Reeve, 1854) comb. nov., L. madagascariensis (W. Wood, 1828) comb. nov., L. semisulcata semigranosa (Dunker, 1877) comb. nov., L. spinosa (Gmelin, 1791) comb. nov., L. sordida (Hanley, 1845) comb. nov., L. siliqua (Römer, 1870) comb. nov., L. trifasciata (Linnaeus, 1758) comb. nov. and L. victoris (Fischer-Piette, 1942) comb. nov.