Evaluating taxonomic inflation: towards evidence-based species delimitation in Eurasian vipers (Serpentes: Viperinae)

Abstract

<jats:title>Abstract</jats:title> <jats:p>The designation of taxonomic units has important implications for the understanding and conservation of biodiversity. Eurasian vipers are a monophyletic group of viperid snakes (Serpentes, Viperinae), currently comprising four genera (<jats:italic>Daboia</jats:italic>, <jats:italic>Macrovipera</jats:italic>, <jats:italic>Montivipera</jats:italic> and <jats:italic>Vipera</jats:italic>) and up to 40 species. Taxonomic units have been described using a wide variety of methods and criteria, and consequently, considerable controversy still surrounds the validity of some currently listed species. In order to promote a consensus- and evidence-based taxonomy of Eurasian vipers, we analysed published mitochondrial and nuclear DNA sequences for this group to reconstruct phylogenetic relationships among currently recognized viper species. We also compiled information on external morphology to assess their morphological distinctiveness. Phylogenetic inference based on mtDNA sequences shows contrasting levels of divergence across genera and species and identifies several instances of non-monophyly in described species. Nuclear DNA sequences show extremely low levels of genetic variation, with a widespread pattern of allele sharing among distant species, and even among genera. Revision of morphological data shows that most species designations rely on scalation traits that overlap extensively among species of the same genus. Based on our combined assessment, we recognize 15 taxa as valid species, three taxa which likely represent species complexes, 17 taxa of doubtful validity as species, and five taxa for which species status is maintained but further research is highly recommended to assess taxonomic arrangements. We stress the need to implement integrative taxonomic approaches for the recognition of evidence-based taxonomic units in Eurasian vipers.</jats:p>

Thermal melanism explains macroevolutionary variation of dorsal pigmentation in Eurasian vipers

“…1): first, we counted the total number of dorsal marks (DM, quantified as the number of angles of the dorsal pattern at its right side, excluding the head and the tail), which is a classic colouration trait in vipers (e.g. 19,21,27,39 ); second, we calculated a weighed pigmentation index (WPI) that quantified the number of dark-pigmented vs. background light-coloured dorsal scales in a standardized area, by extending the protocol implemented by 19 . Specifically, we delimited a sampling rectangle in the central part of the dorsal area of each specimen, with a length of ten dorsal scales (across the length of the body) and a width (N sample ) proportional to the total number of transversal rows of scales of each species (see Table S1).…”

“…For the phylogenetic reconstruction, we used the mitochondrial DNA dataset and the methodology applied in 21 . The dataset included seven mitochondrial gene fragments (CR-control region; COI-cytochrome c oxidase subunit I; cytb-cytochrome b; ND2-NADH dehydrogenase subunit 2; ND4-NADH dehydrogenase subunit 4; ND5-NADH dehydrogenase subunit 5; 16S-mitochondrial gene coding for 16S rRNA) and 93 evolutionary units representing most species/lineages within the group.…”

“…The dataset included seven mitochondrial gene fragments (CR-control region; COI-cytochrome c oxidase subunit I; cytb-cytochrome b; ND2-NADH dehydrogenase subunit 2; ND4-NADH dehydrogenase subunit 4; ND5-NADH dehydrogenase subunit 5; 16S-mitochondrial gene coding for 16S rRNA) and 93 evolutionary units representing most species/lineages within the group. Sequences were obtained from GenBank or generated by 21 and selected according to their origin (concatenation was only performed when sequences originated from the same lineage or geographic location). Phylogenetic relationships and the time of divergence among species were inferred using Bayesian Inference (BI) as implemented in BEAST v 1.7.5 40 .…”

“…A strict molecular clock and a Yule model were used as tree priors. Molecular dating relied on a single calibration point: the split of Vipera-Daboia and Macrovipera-Montivipera dated at 26 Mya (lognormal distribution: mean = 26, sd = 0.07) 21 . Three independent runs of 100 million generations were performed, sampling trees and parameter estimates every 10,000 generations with 10% of the trees discarded as burn-in.…”

“…Eurasian vipers are a highly diversified group of terrestrial venomous snakes (encompassing 4 genera and about 39 species) distributed across a wide variety of climates and environments (e.g. from arid Mediterranean to boreal, and from lowland to high elevation mountain ranges) in North Africa and Eurasia 20 , 21 . Although with distinct shape configurations (e.g.…”