Invasive and non-invasive lineages in Xenostrobus (Bivalvia: Mytilidae)

Abstract

The mussel genus Xenostrobus comprises eight named extant species from the Indo-West Pacific, including Xenostrobus inconstans, Xenostrobus pulex and Xenostrobus securis from Australia, the latter two also occurring in New Zealand. Xenostrobus species are predominantly restricted to estuaries or sheltered marine habitats although X. pulex inhabits the rocky intertidal on open coasts. Xenostrobus has recently been suggested to be congeneric with the freshwater invasive species Limnoperna fortunei. Xenostrobus securis is itself invasive in the Far East and Europe. This study employed DNA sequences from cytochrome c oxidase (COI), the D1 expansion region of 28S rRNA and the internal transcribed spacers of the ribosomal cistrons to investigate species relationships and habitat transitions in Australasian Xenostrobus. It is unlikely that Xenostrobus and Limnoperna are congeneric as their COI sequences are very different. There was unexpected complexity in defining Xenostrobus species. Xenostrobus pulex from New Zealand is probably a distinct species to the Australian taxon of that name with the name X. neozelanicus available for that taxon. Xenostrobus inconstans and Australian X. pulex were not reciprocally monophyletic in COI analyses. The phylogeography of the COI haplotypes of X. securis suggests that it may be a cryptic species complex, although this possibility could not be confirmed by sequences of the other genes.

Keywords:

• cytochrome c oxidase
• internal transcribed spacer
• mussels
• biological invasions
• habitat transitions

Acknowledgements

We thank two anonymous referees for comments on a previous version of this manuscript. We are grateful to Drs Rosemary Golding, Francesco Criscione and Peter Middelfart for assistance with collection and Ms Tina Reutelshöfer for assistance with DNA extractions. We thank Sue Lindsay for specimen photography. We thank the Australian Museum and the N.S.W. Environmental Trust (Grant 2008/RD/0071) for supporting this research financially. Collections for this project were undertaken under Permits F86/2163(A) (New South Wales Fisheries Research Permit), 7118 (Tasmania DPIW permit) and RP972 (Victoria General Research Permit).