High amphibian diversity related to unexpected environmental values in a biogeographic transitional area in north-western Mexico

Abstract

Amphibian diversity and distribution patterns in Sinaloa state (north-western Mexico) were assessed from the Global Amphibian Assessment database (GAA-2010). A geographic information system (GIS) was used to evaluate diversity based on distribution maps of 41 species, associated with environmental data. The highest α and γ-diversities were identified in the south-eastern portion of the state, in mountain zones with a warm sub-humid climate, whereas the greatest β-diversity (multiplicative formulation) was aggregated in patches in the western portion of the state in mountains with temperate climates. A cluster analysis and Mantel test showed a strong association of Sorensen's dissimilarity (additive formulation of β-diversity) with climate and soil moisture categories rather than physiographic categories. Additionally, the partition of Sorensen´s dissimilarity into its components (turnover and nestedness) showed a gradient of species turnover related to contrasting climate units and a marked pattern of nestedness between the middle mountains and the coastal plain. The results of the study suggest that the highest α and β-diversity values occur in the middle-humidity range as well in the transitional-climate categories. This pattern is unusual for amphibian distributions because the highest global and regional amphibian diversities are typically related to high humidity values and climate stability (warm and wet most of the year). This particular pattern, occurring in a transitional area, encourages further biological and ecological studies to clarify the status of amphibian populations and support conservation measures.

Potential Distribution of the Long-tailed Rattlesnake, <em>Crotalus stejnegeri </em>Dunn 1919 (Squamata: Viperidae): A Rare and Under-sampled Species

“…The observed distribution patterns of C. stejnegeri may align with the typical reproductive behavior of rattlesnake species in North America, as well as the warm and humid conditions characteristic of the south-central region of Sinaloa's tropical dry forest (Serrano et al 2014). These factors likely contribute to shaping the distribution of the species.…”

“…Low probability zones of species presence are represented by blue shades, while reddish colors indicate high habitat suitability, predominantly concentrated in the foothills of the SMO spanning from Sinaloa to the northern part of Nayarit. These regions exhibit high habitat suitability possibly due to the dominance of tropical dry forest (Serrano et al 2014;Woolrich-Piña et al 2016), the prevalent vegetation type where the majority of the species' records have been documented (Figure 2B; GBIF 2024). These results suggest that C. stejnegeri has no affinity for low elevation zones, contrary to the information presented by Campbell and Lamar (2024) for Nayarit.…”

“…After a reassessment of multicollinearity, the variable Bio11 was excluded, but Bio15 was retained due to its representation of seasonality data (see Appendix). Despite its high multicollinearity, it was decided not to exclude this variable because Sinaloa has pronounced seasonality (Serrano et al 2014) and contains the majority of C. stejnegeri records. In this second analysis, none of the variables showed a significant VIF index (< 3) and there was no evidence of a positive linear correlation coefficient ≤ 0.5 between them.…”

Potential Distribution of the Long-Tailed Rattlesnake Crotalus stejnegeri Dunn 1919 (Squamata: Viperidae): A Rare and Under-Sampled Species

“…Following a reassessment of multicollinearity, the variable Bio11 was excluded, but Bio15 (Table 1) was retained due to its representation of seasonality data. Despite its high multicollinearity, we decided not to exclude this variable because Sinaloa exhibits pronounced seasonality (Serrano et al, 2014), and it contains the majority of C. stejnegeri records. Therefore, it is plausible that this bioclimatic variable plays a role in influencing the species' distribution.…”

Pathogen Risk Analysis for Wild Amphibian Populations Following the First Report of a Ranavirus Outbreak in Farmed American Bullfrogs (Lithobates catesbeianus) from Northern Mexico

“…The present study describes an outbreak of ranavirus disease in a captive colony of American bullfrogs ( Lithobates catesbeianus ) in the Mexican province of Sinaloa. Sinaloa is located in a transitional zone in the Pacific coast of Mexico and is home to at least 40 amphibian species, among them, salamanders of the families Ambystomatidae (1 species) and Plethodontidae (1 species), and anurans belonging to Bufonidae (9 species), Craugastoridae (4 species), Eleutherodactylidae (4 species), Hylidae (11 species), Leptodactylidae (1 species), Mycrohylidae (3 species), Pelobatidae (1 species), and Ranidae (5 species) [18]. Around 10% of the species from these families show evidence of population declines, 80% are considered stable and for the remaining 10% no information is available [1].…”