Quem são as Lygophis (Squamata : Dipsadidae) de Alagoas?: uma abordagem integrativa para elucidar sua identidade taxonômica

Abstract

The snake genus Lygophis includes eight terrestrial and diurnal species, being widely distributed in the Neotropics (from Panama to Argentina). Six species of Lygophis have confirmed records for Brazilian territory, with no records for the state of Alagoas. Furthermore, a recent study did not predict Alagoas as an area with environmental suitability for the occurrence of Lygophis. Researchers from the Natural History Museum of the Federal University of Alagoas (MHN-UFAL) collected individuals of Lygophis in Craíbas and Santana do Ipanema, Alagoas. Therefore, this study aimed to determine the taxonomic identification of these individuals through an integrative approach, combining morphological and molecular data. Ten specimens incorporated into the MHN-UFAL Herpetological Collection and previously identified as Lygophis sp. were analyzed. Ten meristic and four morphometric characters were measured. The number of dorsal scales (17 in the anterior third, 17 in the middle and 15 in the posterior third), eight supralabials, 165 to 172 ventrals, 62 to 74 subcaudals, one preocular, two posttemporals, nine infralabials and the presence of an entire anal plate were the counts obtained and match the diagnosis of Lygophis paucidens proposed by Dixon (1989) and Lema (1989). The snout-vent length of 250 to 380mm, the body length of 66 to 135mm, the head length of 9.8 to 20.63mm and the head width of 4.74 to 10.78mm are measurements also found in L. paucidens. A Univariate Analysis of Variance (ANOVA) was performed to verify the existence of sexual dimorphism. The Lygophis collected in Alagoas did not show sexual dimorphism, as the F and p values were not significant in relation to the morphometric characters analyzed. In the molecular approach, seven tissue samples previously incorporated into the MHN UFAL Tissue Bank were used for amplification of the mitochondrial structural gene 16S rRNA (318 base pairs) and the nuclear c-mos gene (360 base pairs). These sequences were aligned with sequences from congeners and sister genera, and the phylogenetic trees were rooted with Psomophis genimaculatus (16S rRNA) and Magliophis exiguum (c-mos). Bayesian inference analyzes using the TRN+G and HKY evolutionary model for 16S rRNA and c-mos respectively confirmed that Lygophis from Alagoas form a monophyletic group. Furthermore, Lygophis from Alagoas grouped with Lygophis paucidens available in GenBank, showing no genetic divergence between them in the c-mos gene and a genetic divergence of 6.8% with L. dilepis in the 16S rRNA gene fragment. Thus, by integrating morphological and molecular data, this study confirms the first record of Lygophis paucidens for the state of Alagoas. This record expands the geographical distribution of the species by 620 km to the Northeast of its closest occurrence, in the municipality of Gentio do Ouro, in the state of Bahia, and contributes to reducing the Wallacean deficit.