Testing the contribution of individual genes in mitochondrial genomes for assessing phylogenetic relationships in Vetigastropoda

Phylogenetic analyses for molluscs frequently make use of the mitochondrial (mt) markers COX1, 12S and 16S, in part because of the availability of universal primers (e.g. Plazzi & Passamonti, 2010; Williams et al., 2010; Aktipis & Giribet, 2011; Plazzi et al., 2011; Wakabayashi et al., 2012). Recent phylogenetic studies have expanded on gene sampling, sequenced entire mt genomes and undertaken phylogenetic analyses using all protein-coding and rRNA genes for determining relationships within Mollusca, generally resulting in well-resolved trees with highly supported nodes (e.g. White et al., 2011; Williams, Foster & Littlewood, 2014; Uribe et al., 2015). However, several papers have pointed out that trees based purely on mtDNA can produce erroneous deep relationships between different molluscan taxa (Stoger & Schrodl, 2013; Bernt et al., 2013a). This is perhaps unsurprising, given that mtDNA generally evolves more quickly than the nuclear genome (Burton & Barreto, 2012), and deeper relationships may therefore be beyond the saturation point of mtDNA. However, with the recent development of next-generation sequencing, entire mt genomes can be sequenced rapidly and relatively cheaply. It is therefore important to determine the utility and reliability of the mt genome as a marker for phylogenetic analysis.