Sunday, April 23, 2017

[Herpetology • 2017] Species Delimitation of the Blue-spotted Spiny Lizard within A Multilocus, Multispecies Coalescent Framework, Results in the Recognition of A New Sceloporus Species; Sceloporus gadsdeni


 DOI: 10.1016/j.ympev.2017.04.004 

Highlights
• Reciprocal monophyly supported clades were found for Sceloporus cyanostictus.
• Parametric coalescent-based method confirms two different lineages.
• A new species of Sceloporus is recognized and described.

Abstract
Species delimitation is a major topic in systematics. Species delimitation methods based on molecular data have become more common since this approach provides insights about species identification via levels of gene flow, the degree of hybridization and phylogenetic relationships. Also, combining multilocus mitochondrial and nuclear DNA leads to more reliable conclusions about species limits. Coalescent-based species delimitation methods explicitly reveal separately evolving lineages using probabilistic approaches and testing the delimitation hypotheses for several species. Within a multispecies, multilocus, coalescent framework, we were able to clarify taxonomic uncertainties within S. cyanostictus, an endangered lizard that inhabits a narrow strip of the Chihuahuan Desert in Mexico. We included, for the first time in a phylogenetic analysis, lizards from the three populations of S. cyanostictus recognized so far (East Coahuila, West Coahuila and Nuevo León). Phylogenetic analysis corroborates the hypothesis of two separately evolving lineages, i.e. the East and West Coahuila populations, as proposed in a previous study. We also found a distant phylogenetic relationship between the lizards from Nuevo León and those of East and West Coahuila. Finally, based on the species delimitation results, we propose and describe a new species of SceloporusSceloporus gadsdeni sp. nov.

Keywords: BP&P; Chihuahuan Desert; Molecular data; Systematics; Sceloporus; Taxonomic uncertainties


Fig. 1. Known distribution of Sceloporus cyanostictus. 

Sceloporus gadsdeni Castañeda-Gaytán & Díaz-Cárdenas sp. nov. 
(Lagoon Spiny Lizard)

Diagnosis: This species differs from S. cyanostictus in the dorsal color pattern (live), which is completely green with two dominant tonalities (metallic green and turquoise). The ventral pattern has a blue patch that joins in the middle of the belly and the chest with black borders in males; in contrast, in Scyanostictus the chest and undersurfaces of arms are pale grayish blue with melanin specks, each flank has a poorly defined bluish black belly patch sometimes without contact in the middle of the belly. According to currently available published information, S. cyanostictus from eastern Coahuila has 6 superciliars and 6 infralabials (Axtell and Axtell, 1971), while S. gadsdeni has 4 superciliar scales on each side of the head and 5 infralabials with uncertainty on this character due to sample size (Table 2).

The distribution of S. gadsdeni is restricted to the Sierras Texas, Solis and San Lorenzo mountain ranges in southwestern Coahuila, and this species inhabits rock walls, boulders and canyons. These mountains are separated from the location of S. cyanostictus by ca. 190 km as the crow flies and immersed within the low Mayran Basin.


Etymology: This species is named in honor of Hector Gadsden, a researcher who has made praiseworthy contributions to the ecology and conservation of the herpetofauna of La Comarca Lagunera and the Chihuahuan Desert. The suggested common name alludes to its restricted distribution within the La Comarca Lagunera region.


Brenda Díaz-Cárdenas, Eduardo Ruiz-Sanchez, Patricia Castro-Felix, Gamaliel Castañeda-Gaytán, Sergio Ruiz-Santana and Héctor Gadsden. 2017. Species Delimitation of the Blue-spotted Spiny Lizard within A Multilocus, Multispecies Coalescent Framework, Results in the Recognition of A New Sceloporus Species. Molecular Phylogenetics and Evolution. In Press.  DOI: 10.1016/j.ympev.2017.04.004

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