Ten new complete mitochondrial genomes of pulmonates (Mollusca: Gastropoda) and their impact on phylogenetic relationships

The structural features of the 10 new mitochondrial genomes are provided. All genomes share similar gene orders. Phylogenetic analyses were performed including the 10 new genomes and 17 genomes from Genbank (outgroups, opisthobranchs, and other pulmonates). Bayesian Inference and Maximum Likelihood analyses, based on the concatenated amino-acid sequences of the 13 protein-coding genes, produced the same topology. The pulmonates are paraphyletic and basal to the opisthobranchs that are monophyletic at the tip of the tree. Siphonaria, traditionally regarded as a basal pulmonate, is nested within opisthobranchs. Pyramidella, traditionally regarded as a basal (non-euthyneuran) heterobranch, is nested within pulmonates. Several hypotheses are rejected, such as the Systellommatophora, Geophila, and Eupulmonata. The Ellobiidae is polyphyletic, but the false limpet Trimusculus reticulatus is closely related to some ellobiids.Despite recent efforts for increasing the taxon sampling in euthyneuran (opisthobranchs and pulmonates) molecular phylogenies, several of the deeper nodes are still uncertain, because of low support values as well as some incongruence between analyses based on complete mitochondrial genomes and those based on individual genes (18S, 28S, 16S, CO1). Additional complete genomes are needed for pulmonates (especially for Williamia, Otina, and Smeagol), as well as basal heterobranchs closely related to euthyneurans. Increasing the number of markers for gastropod (and more broadly mollusk) phylogenetics also is necessary in order to resolve some of the deeper nodes -although clearly not an easy task. Step by step, however, new relationships are being unveiled, such as the close relationships between the false limpet Trimusculus and ellobiids, the nesting of pyramidelloids within pulmonates, and the close relationships of Siphonaria to sacoglossan opisthobranchs. The additional genomes presented here show that some species share an identical mitochondrial gene