Genetic diversity and population genetic structure in giant earthworm Rhinodrilus alatus (Annelida: Clitellata: Glossoscolecidae)

Rhinodrilus alatus (Righi, 1971) is a giant earthworm (“minhocuçu”) endemic to Southeast Brazil savannah that has long been exploited as fishing bait, however such extractive activity results in social and environmental impacts as well as negative effects on the species. Genetic diversity, population genetic and geographic structures of R. alatus were characterized by sequencing of the mitochondrial gene cytochrome c oxidase I (COI) and a nuclear segment including 5.8S rRNA gene and the internal transcribed spacers 1 (ITS1) and 2 (ITS2). We sequenced 75 R. alatus and 6 Rhinodrilus motucu individuals collected at 21 sites. Genetic diversity was evaluated based on haplotype and nucleotide diversity, and average number of nucleotide differences. Population genetic and geographic structure was characterized with Mantel tests, spatial analysis of molecular variance (SAMOVA), and phylogenetic analysis (maximum likelihood, Bayesian inference, and median joining). High genetic diversity was found for this species with 53 haplotypes in the COI gene and 22 haplotypes for the ITS1-5.8S-ITS2 segment suggesting six and four lineages, respectively. Moderate population genetic structure was indicated by the spatial distribution of lineages and Mantel tests results. High genetic diversity associated with genetic and geographic population structure points to a low dispersal rate for the species, as described for other earthworms. We characterized less frequent lineages, which were collected on the periphery of the dispersal area of the species. Conservation of the largest possible number of lineages particularly those less common will be fundamental for maintaining the genetic diversity of the species.