Systematic relationships and taxonomy of Suncus montanus and S. murinus from Sri Lanka

Here we use nuclear and mitochondrial DNA sequence data, combined with morphometric analyses, to clarify the systematic relationships and taxonomy of two complex species of shrews, Suncus montanus and S. murinus, in Sri Lanka. We find that subspecies of S. murinus, Suncus murinus murinus from Anuaradhapura and S. m. caerulescens from Colombo, show little or no genetic difference in the mitochondrial (cytochrome-b and 16SrRNA) and nuclear (Rag 1, aldolase C and EF-1 alpha intron) genes, confirming their classification as a single species. However, two populations of S. murinus from Peradeniya and Udawalawe are identified as putative hybrids of S. murinus and S. montanus. Shrews collected from Peradeniya are best described as a population of S. murinus, but could be identified as S.m. kandianus using morphological features. Nuclear DNA sequence data places this population in a clade with other S. murinus, but mtDNA sequences of the population nests within a clade of S. montanus haplotypes. This discordant pattern of nuclear and mitochondrial genes suggests either hybridization between S. murinus and S. montanus or introgression of S. montanus mitochondrial DNA into S. m. kandianus. S. m. murinus from Udawalawe, which shows no distinct morphological difference from S. m. murinus from Anuradhapura, falls in the clade of S. murinus in both nuclear and mitochondrial trees. In the nuclear gene tree however, S. m.murinus from Udawalawe is placed as a sister taxon to the clade including other S. murinus. Rag 1 gene sequences in Udawalawe individuals suggest recombination of S. murinus and S. montanus DNA within the gene. However, additional nuclear genes are necessary to study the extent of the hybridization of S. murinus and S. montanus.