Phylogeography of the Colombian water snake Helicops danieli Amaral, 1938 (Reptilia, Squamata, Dipsadidae) with comments on the systematics and evolution of the genus Helicops Wagler, 1828

Abstract

The genus Helicops Wagler, 1828 comprises 20 species of semiaquatic snakes. It is mostly distributed in the cis-Andean region of South America, with only two trans-Andean species (H. danieli, H. scalaris). Helicops danieli is endemic to Colombia and occurs through most of the trans-Andean region. Herein two mitochondrial and two nuclear genomic markers were sequenced for 16 samples of H. danieli across most of its distribution range to understand its phylogeography. A dated tree was also generated with additional sequences from previous studies to infer the divergence times between H. danieli and its cis-Andean congeners and of lineages within H. danieli. Using previously published data, ancestral states were estimated for putative phenotypic synapomorphies for the major clades of Helicops. For H. danieli, four clades corresponding to the main river basins within its distribution were recovered. Our dated tree suggests that the ancestor of H. danieli diverged from its closest congeners in the late Miocene (8.7 Mya), which can be associated with the closure of the Andalucia Pass, south of the Eastern Cordillera. Divergence within H. danieli commenced 1.1 Mya. Within the genus Helicops, two distinct hemipenial morphologies were observed, which are suggested as putative synapomorphies for the two most basal clades. Recognition of these two clades as distinct subgenera, Helicops sensu stricto and Tachynectes Fitzinger, 1843 is proposed. For the junior homonym Tachynectes von der Mark, 1863, rarely applied to fossil fishes, the replacement name Ichthyotachynectes nom. nov. is introduced. Furthermore, the evolution of another four phenotypic traits in Helicops and their phylogenetic utility are discussed.