Mitochondrial genomes and phylogenomic analysis of Plectostylus broderipii and Bostryx erythrostoma (Gastropoda, Stylommatophora, Orthalicoidea) from the Atacama Desert, Chile.

We report the first mitochondrial genomes of two Orthalicoidea land snails from the Atacama Desert of northern Chile, Bostryx erythrostoma and Plectostylus broderipii. Using Illumina short-read sequencing, we assembled and annotated mitochondrial genomes of 15,525 bp and 14,978 bp, respectively, with strong A+T bias (69.75% in B. erythrostoma; 72.08% in P. broderipii). Both genomes retain the standard metazoan mitochondrial complement of 37 genes, including 13 protein-coding genes (PCGs), 22 tRNAs, and two rRNAs, with differences in total length mainly due to variation in non-coding regions rather than coding-gene content. Comparative analysis showed that the two species share the same order of the 13 PCGs, whereas differences are concentrated in local tRNA/rRNA rearrangements and intergenic architecture. Both mitogenomes also exhibit negative AT skew and positive GC skew under a standardized orientation. Phylogenetic inference based on a concatenated 13-PCG nucleotide supermatrix resolved both taxa within Orthalicoidea with strong support: B. erythrostoma grouped with a congeneric Bostryx reference, and this clade clustered with Rabdotus mooreanus and Naesiotus nux, whereas P. broderipii was inferred as sister to this orthalicoid cluster.