Molecular phylogeny of the tribe Philodryadini Cope, 1886 (Dipsadidae: Xenodontinae): Rediscovering the diversity of the South American Racers

Abstract

South American racers of the tribe Philodryadini are a widespread and diverse group of Neotropical snakes with a complex taxonomic and systematic history. Recent studies failed to present a robust phylogenetic hypothesis for the tribe, mainly due to incomplete taxon sampling. Here we provide the most extensive molecular phylogenetic analysis of Philodryadini available so far, including 20 species (83% of the known diversity) from which six were not sampled previously. Our results reveal that Philodryadini is not monophyletic, but instead includes a central Andean clade formed by Philodryas simonsii, P. tachymenoides, and P. amaru, and a southern and cis-Andean clade including all remaining philodryadines. This discovery requires resurrection of two genera as well as erection of a new tribe of Xenodontinae for the central Andean clade. Within the southern and cis-Andean radiation, our analyses resolve a basal dichotomy separating two main lineages: Clade A, containing the Common Green Racers P. laticeps and P. viridissima and the South American Vine snakes P. georgeboulengeri and P. argentea; and Clade B, including the remaining species of Philodryas sensu stricto. We resurrect the genera Chlorosoma and Xenoxybelis to better represent the monophyly of lineages within the southern and cis-Andean clade.

There and back again: when and how the world's richest snake family (Dipsadidae) dispersed and speciated across the Neotropical region

“…Similarly, Saphenophis and the recently described trans‐Andean genus Incaspis (not sampled in our analysis) have been recovered as independent and old lineages (tribes Saphenophiini and Incaspidini). The latter is recovered as sister to the cis‐Andean tribes Tropidodryadini and Philodryadini (Arredondo et al., 2020), likely suggesting other dispersal events between both regions in the early Oligocene, before the mountain uplift.…”

“…Similarly, Saphenophis and the recently described trans-Andean genus Incaspis (not sampled in our analysis) have been recovered as independent and old lineages (tribes Saphenophiini and Incaspidini). The latter is recovered as sister to the cis-Andean tribes Tropidodryadini and Philodryadini(Arredondo et al, 2020), likely suggesting other dispersal events between both regions in the early Oligocene, before the mountain uplift.Our results show that current biogeographical patterns of the family Dipsadidae, the most species-rich snake clade in the world, have been shaped by complex evolutionary and geological processes. Our reconstructed model recovered an Asian origin for the Dipsadidae family and potential significant palaeogeographical events such as Eocene land bridges, Andean uplift and the formation of the Panama isthmus.…”

The Venom Composition of the Snake Tribe Philodryadini: ‘Omic’ Techniques Reveal Intergeneric Variability among South American Racers

“…The snake family Dipsadidae belongs to a very diverse clade known as Caenophidia (advanced snakes), and with approximately 700 described species [1], this family accounts alone for 20% of the extant diversity of snake in the world [2]. Dipsadids usually present opisthoglyphous maxillary dentition, which is characterized by grooved teeth located in the posterior region of the mouth, in association with venom glands [3,4]. Despite producing a complex set of toxins [5], Dipsadidae has not been comprehensively studied as other snake families have, such as Viperidae and Elapidae [6].…”

Increasing taxon sampling suggests a complete taxonomic rearrangement in Echinantherini (Serpentes: Dipsadidae)

“…within Dipsadidae. As a consequence, several taxonomic changes at generic and suprageneric levels were advanced as a way to adequately reflect the recovered evolutionary history (e.g., Zaher et al, 2009Zaher et al, , 2018Grazziotin et al, 2012;Pyron et al, 2015;Arredondo et al, 2020;Trevine et al, 2022). However, several tribes that are well-supported molecularly and morphologically are still poorly sampled in molecular phylogenies, hampering any attempt to provide reliable hypotheses of phylogenetic relationships within these groups.…”