Patterns of genetic variation in Pacific island land snails: the distribution of cytochrome b lineages among Society Island Partula

Abstract

The radiation of Partula land snails has produced a large array of distinct morphological, ecological and behavioural types occupying many tropical volcanic islands in the Pacific Ocean. Within the Society Islands of French Polynesia, the mode of evolution is thought to have involved a single colonization event on each island, with later speciation occurring largely in situ. The present study examines genetic variation in the mitochondrial cytochrome b gene among taxa within the Society Island archipelago. Levels of intraspecific variation are found to be high, but variation among species is sometimes small. Mitochondrial variants do not always cluster according to island and some species are found to be polyphyletic in the cytochrome b tree, despite other morphological and molecular evidence that strongly supports their monophyly. A possible explanation for the polyphyly of species is that different variants are derived from ancestral mitochondrial polymorphisms that have been retained despite speciation events. Although it is possible that there has been some gene flow among islands, the distribution of mitochondrial lineages across islands strongly indicates that their origins predate the colonization of the islands in the study, and that they are very unlikely to have evolved entirely in situ.

Evaluating DNA barcoding criteria using African duiker antelope (Cephalophinae) as a test case

“…The recent divergence of species within this subfamily (Vrba 1995) presents a challenge to effective species delimitation because recently diverged taxa may fail to constitute reciprocally monophyletic groups. This could be attributed to incomplete lineage sorting and/or ongoing or recent gene flow between sister taxa (Crandall and Fitzpatrick 1996;Funk and Omland 2003;Goodacre and Wade 2001;Renoult et al 2009 Conserv Genet (2011) 12:1173-11821177 Tree based analyses of the COX1 data revealed a lack of monophyly for C. callipygus, C. ogilbyi and C. weynsi, as has been reported in earlier studies using other molecular markers (Jansen van Vuuren and Robinson 2001; Ntie et al 2010). As has also been observed in other studies based on mitochondrial COX1 or 12S ribosomal DNA sequences (Eaton et al 2010;, C. callipygus here appears to be composed of two distinct sub-clades that are sister to one another.…”

The snails the dinosaurs saw: are the pleurocerid populations of the Older Appalachians a relict of the Paleozoic Era?

“…However, double-digit values of % sequence divergence within molluscan populations, such as those shown in Figs 3 and 4, are not entirely unprecedented. The phenomenon has been reported within numerous populations of land snails (Thomaz et al 1996, Goodacre and Wade 2001, Guiller et al 2001, Haase et al 2003 and in the special case of doubly-uniparental inheritance in bivalves (Rawson …”

Evolutionary history of a vanishing radiation: isolation-dependent persistence and diversification in Pacific Island partulid tree snails

“…Consistent with this view, examples of Moorean/Tahitian mt polyphyly have been interpreted either as being due to convergent molecular evolution (for restriction fragment length polymorphism data [23,50], or to retained ancestral mt polymorphisms [51-53], rather than being products of inter-island gene flow involving multiple discrete lineages. However, both of these non-gene flow interpretations are problematic.…”

“…The goal of our study was to build on Goodacre’s pioneering molecular phylogenetic work [44,51,55] by constructing higher-resolution broad scale (range wide) and fine scale (within-Society Island archipelago) partulid phylogenetic relationships for nuclear and mitochondrial genetic markers. Although our geographically- and taxonomically-enhanced sampling scheme was far from exhaustive, and heavily weighted toward Moorean and Tahitian taxa (Table 1), the incorporation of museum and captive (zoo) samples allowed us to genotype numerous extinct and extirpated taxa that span the family’s range; the Solomon Islands being the only major archipelago that lacked a representative.…”