Generation of large mitochondrial and nuclear nucleotide sequences and phylogenetic analyses using high-throughput short-read datasets for endangered Placostylinae snails of the southwest Pacific

Abstract

ABSTRACT Placostylinae are a sub-family of terrestrial land snails endemic to the southwest Pacific. Some species are harvested for food, and others are critically endangered. Here we assemble and characterise complete mitochondrial genomes, as well as three nuclear markers (partial 45S ribosomal cassettes and the histone genes H3 and H4) of five snail species from three geographical regions (New Zealand, New Caledonia and the Solomon Islands). Mitogenomes of Placostylinae snails ranged between 14,544 bp and 14,711 bp, with minor variation in the position of tRNA tyrosine (Y) and tRNA tryptophane (W). The 45S ribosomal cassette contained intra-genomic nucleotide variation in ITS2. Cassettes containing histone genes H3 and H4 and their non-transcribed spacer region were assembled for three species, with the two genes coded in the same direction. Phylogenetic analysis on this large dataset (mitochondrial genome + nuclear markers) supported geographical clustering of species but could not confidently infer monophyly of the four Placostylus species with respect to Eumecostylus cleryi. Analysis based on shorter cytochrome c oxidase sequences with a wider taxon sampling found species representing the genera Eumecostylus and Placocharis were nested within the phylogenetic diversity of Placostylus. Multi-locus phylogenetic analysis containing mitochondrial and nuclear sequences did not support monophyly of Placostylinae.