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<p>Environmental and genetic factors play pivotal roles in shaping adaptive evolution and driving phenotypic variation within populations. To assess how varying environmental conditions influence morphological traits, it is essential to analyze populations at a microevolutionary scale. This study investigated Mexican dusky rattlesnakes (<i>Crotalus triseriatus</i>) across three sky island volcanoes in central Mexico: Malinche National Park, Ajusco, and Pico de Orizaba. We examined the variations in body length and head shape among the populations and evaluated their correlations with environmental factors, including bioclimatic variables, land use, proximity to water, vegetation cover, and operative temperatures (species-specific thermal conditions within their habitat). Our findings, collected during monthly visits during active seasons (March to October), revealed that the snakes from Malinche National Park exhibited significantly greater total length (TaL = 47.36 ± 1.44&#xa0;cm, F = 12.69, <i>p</i> &lt; 0.0001) and weight (W = 117.18 ± 6.44&#xa0;g, F = 36.07, <i>p</i> &lt; 0.0001) than did those from Ajusco and Pico de Orizaba. Additionally, this population displayed the most distinct head morphologies, characterized by a 10% greater anterior constriction near the supraocular scale base compared to both other sites. Two-block partial least squares (2B-PLS) analysis revealed significant correlations between phenotypic variation and environmental factors, particularly altitude (r<sup>2</sup> = 0.491), annual precipitation (r<sup>2</sup> = 0.770), aspect (r<sup>2</sup> = 0.284), and proximity to water (r<sup>2</sup> = -0.238). Notably, while proximity to water was negatively correlated with head morphology, the biomass of the species was not directly water dependent. <i>Crotalus triseriatus</i> is a small to medium-sized rattlesnake inhabiting high-altitude forests where it relies on cool, humid conditions and like all predators would depend on prey availability for growth and reproduction. This study underscores the role of local environmental heterogeneity in driving phenotypic divergence among populations and highlights the importance of integrating morphometric and ecological analyses for understanding adaptive strategies in fragmented landscapes.</p>

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Mexican dusky rattlesnakes (Crotalus triseriatus) on Mexican sky islands: Morphometric variation and operative temperature relationships with local environmental variables

  • 期刊论文

  • 发表日期：

    2025年3月10日

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  • Carmen Caballero-Viñas,
  • Sebastián Arenas,
  • José Luis Jaramillo-Alba,
  • Hibraim Adán Pérez-Mendoza,
  • Javier Manjarrez,
  • Hublester Domínguez-Vega,
  • Yuriana Gómez-Ortiz,
  • Jonas Alvarez-Lopetez-Tello,
  • María Elena Estrada-Zúñiga,
  • Armando Sunny

摘要

Environmental and genetic factors play pivotal roles in shaping adaptive evolution and driving phenotypic variation within populations. To assess how varying environmental conditions influence morphological traits, it is essential to analyze populations at a microevolutionary scale. This study investigated Mexican dusky rattlesnakes (Crotalus triseriatus) across three sky island volcanoes in central Mexico: Malinche National Park, Ajusco, and Pico de Orizaba. We examined the variations in body length and head shape among the populations and evaluated their correlations with environmental factors, including bioclimatic variables, land use, proximity to water, vegetation cover, and operative temperatures (species-specific thermal conditions within their habitat). Our findings, collected during monthly visits during active seasons (March to October), revealed that the snakes from Malinche National Park exhibited significantly greater total length (TaL = 47.36 ± 1.44 cm, F = 12.69, p < 0.0001) and weight (W = 117.18 ± 6.44 g, F = 36.07, p < 0.0001) than did those from Ajusco and Pico de Orizaba. Additionally, this population displayed the most distinct head morphologies, characterized by a 10% greater anterior constriction near the supraocular scale base compared to both other sites. Two-block partial least squares (2B-PLS) analysis revealed significant correlations between phenotypic variation and environmental factors, particularly altitude (r2 = 0.491), annual precipitation (r2 = 0.770), aspect (r2 = 0.284), and proximity to water (r2 = -0.238). Notably, while proximity to water was negatively correlated with head morphology, the biomass of the species was not directly water dependent. Crotalus triseriatus is a small to medium-sized rattlesnake inhabiting high-altitude forests where it relies on cool, humid conditions and like all predators would depend on prey availability for growth and reproduction. This study underscores the role of local environmental heterogeneity in driving phenotypic divergence among populations and highlights the importance of integrating morphometric and ecological analyses for understanding adaptive strategies in fragmented landscapes.