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

The genus <i>Helicops</i> 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 (<i>H.danieli</i>, <i>H.scalaris</i>). <i>Helicopsdanieli</i> 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 <i>H.danieli</i> 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 <i>H.danieli</i> and its cis-Andean congeners and of lineages within <i>H.danieli</i>. Using previously published data, ancestral states were estimated for putative phenotypic synapomorphies for the major clades of <i>Helicops</i>. For <i>H.danieli</i>, four clades corresponding to the main river basins within its distribution were recovered. Our dated tree suggests that the ancestor of <i>H.danieli</i> 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 <i>H.danieli</i> commenced 1.1 Mya. Within the genus <i>Helicops</i>, 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, <i>Helicops</i> sensu stricto and <i>Tachynectes</i> Fitzinger, 1843 is proposed. For the junior homonym <i>Tachynectes</i> von der Mark, 1863, rarely applied to fossil fishes, the replacement name <i>Ichthyotachynectes</i> <b>nom. nov.</b> is introduced. Furthermore, the evolution of another four phenotypic traits in <i>Helicops</i> and their phylogenetic utility are discussed.