Mytilus mitochondrial DNA haplotypes in southeastern Australia

Abstract

Mitochondrial DNA (mtDNA) analyses suggest that Southern Hemisphere mussels of the Mytilus edulis species complex include an endemic lineage and invasive genetic elements derived from the Northern Hemisphere species M. galloprovincialis and M. edulis. Haplotypes from these species have been reported in substantial frequencies from South America, South Africa, Western Australia and New Zealand, but only at very low frequencies in Tasmania and the coast near Melbourne in Victoria, the only regions studied in southeastern Australia. Here we investigate cytochrome c oxidase sequences from a wider region in southeastern Australia. Substantial frequencies of Northern Hemisphere Mytilus haplotypes of the female form of the mtDNA were observed, particularly in southern New South Wales. These haplotypes represented a broad range of divergent lineages among the Northern Hemisphere clades. All 3 haplotypes of the male form of mtDNA belonged to the lineage previously identified as the 'European' clade of M. edulis.

Twin introductions by independent invader mussel lineages are both associated with recent admixture with a native congener in Australia

“…Our results confirm that diagnostic methods used to identify hemisphere origins based on mitochondrial loci (e.g. Ab Rahim et al, 2016;Colgan & Middelfart, 2011;Dias et al, 2014) are not a reliable method for differentiating native and introduced…”

Invasive blue mussels threaten regional scale genetic diversity in mainland and remote offshore locations: the need for baseline data and enhanced protection in the Southern Ocean

“…The very clear affinity of the Ocean Patriot (oil rig) mussels with Northern Hemisphere M. galloprovincialis and also the occurrence of Northern M. galloprovincialis genes in some northern NZ populations reveals the extent of the threat posed by nonindigenous species (NIS) in terms of genetic contamination of native mussels at a regional scale in the Southern Hemisphere (e.g. Westfall & Gardner, , ; Colgan & Middelfart, ; Oyarzún et al ., ). The ecological consequences of hybridization and introgression have not been quantified for mussels in most places, but where such work has been conducted the results point to significant fitness differences between the two parental types and also for the hybrids and backcrosses (Gardner, , ; Gardner & Thompson, ; Oyarzún et al ., ).…”

“…The identification in the present study of a distinct Southern Ocean genetic lineage of blue mussels adds to the list of Southern Hemisphere regions, including mainland New Zealand, Australia, and Chile that are either threatened by or are now experiencing hybridization and introgression between native and introduced lineages (e.g. Toro et al ., ; Westfall & Gardner, , ; Colgan & Middelfart, ; Oyarzún et al ., ). This threat is particularly pronounced for remote Southern Ocean islands where population sizes are small compared to mainland populations, there is a history of ship wrecks with the associated risk of accidental introductions (e.g.…”

The coastal marine mollusc fauna of King Island, Tasmania

“…For one of these, Mytilus galloprovincialis, its taxonomic and native status remains uncertain locally, because some Australian populations bear the genetic signature of both native and European ancestry (Colgan & Middelfart 2011). Overall, three species represents a small proportion of the feral species pool in Tasmanian waters, which comprises at least ten shelled species and four nudibranchs (Grove 2014).…”

“…Only two of our species are non-native -the screwshell Maoricolpus roseus and the oyster Crassostrea gigas; and our checklist contains no others, with the possible exception of Mytilus galloprovincialis, whose taxonomic and native status remains uncertain (Colgan & Middelfart 2011).…”