Variación de rasgos, trade-offs y su relación con los límites de distribución: el caso de la lagartija andina Proctoporus lacertus (Gymnophthalmidae) de los Andes de Perú.
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Date
2026
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Universidad de Concepción
Abstract
La variación geográfica de rasgos morfológicos, fisiológicos y comportamentales constituye una expresión fundamental de la biodiversidad, ya que refleja cómo los organismos responden a las presiones selectivas impuestas por el ambiente. En especies ampliamente distribuidas, estas diferencias fenotípicas tienden a expresarse de manera más pronunciada y pueden afectar el desempeño local en términos competitivos, energéticos, conductuales y reproductivos, influyendo en conjunto sobre la persistencia de las poblaciones a lo largo del tiempo. En ectotermos, los rasgos morfológicos como el tamaño corporal no responden a las reglas macroecológicas clásicas, sino que reflejan la interacción entre temperatura, estacionalidad climática, humedad, disponibilidad de recursos y presión de depredación. Asimismo, los rasgos térmicos pueden variar en respuesta a presiones selectivas contrastantes impuestas por la heterogeneidad térmica del ambiente. A su vez, esta variación geográfica puede dar lugar a trade-offs, de modo que las adaptaciones que incrementan la tolerancia ambiental pueden implicar costos en otros componentes del desempeño, como la capacidad competitiva, contribuyendo al establecimiento de los límites del rango de distribución de las especies. En este contexto, en el presente estudio evaluamos cómo Proctoporus lacertus, una lagartija que habita los Andes del sureste de Perú, responde a la heterogeneidad ecológica de la Cordillera de los Andes, integrando la variación del tamaño corporal, los rasgos térmicos y las interacciones competitivas con congéneres en los límites de su rango de distribución. Nuestros resultados evidencian una variación significativa en el tamaño corporal, con individuos de menor tamaño asociados a condiciones más áridas. Además, los rasgos térmicos mostraron respuestas mixtas a lo largo del gradiente altitudinal. La población de mayor elevación presentó un rango de tolerancia térmica más amplio y una mayor tolerancia al frío, mientras que la tolerancia al calor se mantuvo relativamente conservada entre localidades. Asimismo, los rasgos térmicos voluntarios permanecieron mayormente constantes a lo largo del gradiente altitudinal, con excepción de VTmin, que fue menor en la población de mayor elevación. Encontramos que la reducción del tamaño corporal asociada a ambientes áridos tiene consecuencias competitivas. En experimentos de jardín común, los individuos pequeños de P. lacertus fueron competitivamente subordinados frente a P. cf. kiziriani, un congénere de mayor tamaño que habita la porción más elevada y húmeda del límite de distribución de P. lacertus. En cambio, los individuos grandes de P. lacertus fueron competitivamente dominantes frente a P. cf. kiziriani. En conjunto, estos resultados sugieren la existencia de un trade-off evolutivo, en el cual el fenotipo pequeño favorecería la persistencia en ambientes áridos, pero a costa de una menor capacidad competitiva en zonas de contacto con congéneres de mayor tamaño, limitando la expansión de su rango de distribución. Por lo tanto, los límites de distribución de P. lacertus no estarían determinados únicamente por restricciones climáticas directas, sino por la interacción entre adaptación local, trade-offs evolutivos e interacciones bióticas.
Geographic variation in morphological, physiological, and behavioral traits constitutes a fundamental expression of biodiversity, as it reflects how organisms respond to the selective pressures imposed by the environment. In widely distributed species, these phenotypic differences tend to be expressed more pronouncedly and may affect local performance in competitive, energetic, behavioral, and reproductive terms, collectively influencing population persistence over time. In ectotherms, morphological traits such as body size do not necessarily conform to classic macroecological rules, but instead reflect the interaction among temperature, climatic seasonality, humidity, resource availability, and predation pressure. Likewise, thermal traits may vary in response to contrasting selective pressures imposed by environmental thermal heterogeneity. These pressures may be particularly intense in high-elevation environments, where intense nocturnal cooling and high daytime solar radiation generate markedly contrasting thermal conditions. In turn, this geographic variation may give rise to trade-offs, whereby adaptations that increase environmental tolerance may entail costs in other components of performance, such as competitive ability, thereby contributing to the establishment of species’ distributional range limits. Therefore, these trade-offs play an important role in establishing species distribution limits. In this context, the present study evaluated how Proctoporus lacertus, a lizard inhabiting the Andes of southeastern Peru, responds to the ecological heterogeneity of the Andean Cordillera by integrating variation in body size, thermal traits, and competitive interactions with congeners at the limits of its distributional range. Our results revealed significant variation in body size, with smaller individuals associated with more arid conditions. In addition, thermal traits showed mixed responses along the elevational gradient. The high-elevation population exhibited a broader thermal tolerance range and greater cold tolerance, whereas heat tolerance remained relatively conserved among localities. Likewise, voluntary thermal traits remained largely constant along the elevational gradient, with the exception of VTmin, which was lower in the high-elevation population. We also found that the reduction in body size associated with arid environments has competitive consequences. In common garden experiments, small individuals of P. lacertus were competitively subordinate to P. cf. kiziriani, a larger congener that inhabits the higher and more humid portion of the distributional limit of P. lacertus. Conversely, large individuals of P. lacertus were competitively dominant over P. cf. kiziriani. Overall, these results suggest the existence of an evolutionary trade-off, in which the small phenotype may favor persistence in arid environments, but at the cost of reduced competitive ability in contact zones with larger congeners, thereby limiting the expansion of its distributional range. Consequently, the distribution limits of P. lacertus may not be determined solely by direct climatic constraints, but rather by the interaction among local adaptation, evolutionary trade-offs, and biotic interactions.
Geographic variation in morphological, physiological, and behavioral traits constitutes a fundamental expression of biodiversity, as it reflects how organisms respond to the selective pressures imposed by the environment. In widely distributed species, these phenotypic differences tend to be expressed more pronouncedly and may affect local performance in competitive, energetic, behavioral, and reproductive terms, collectively influencing population persistence over time. In ectotherms, morphological traits such as body size do not necessarily conform to classic macroecological rules, but instead reflect the interaction among temperature, climatic seasonality, humidity, resource availability, and predation pressure. Likewise, thermal traits may vary in response to contrasting selective pressures imposed by environmental thermal heterogeneity. These pressures may be particularly intense in high-elevation environments, where intense nocturnal cooling and high daytime solar radiation generate markedly contrasting thermal conditions. In turn, this geographic variation may give rise to trade-offs, whereby adaptations that increase environmental tolerance may entail costs in other components of performance, such as competitive ability, thereby contributing to the establishment of species’ distributional range limits. Therefore, these trade-offs play an important role in establishing species distribution limits. In this context, the present study evaluated how Proctoporus lacertus, a lizard inhabiting the Andes of southeastern Peru, responds to the ecological heterogeneity of the Andean Cordillera by integrating variation in body size, thermal traits, and competitive interactions with congeners at the limits of its distributional range. Our results revealed significant variation in body size, with smaller individuals associated with more arid conditions. In addition, thermal traits showed mixed responses along the elevational gradient. The high-elevation population exhibited a broader thermal tolerance range and greater cold tolerance, whereas heat tolerance remained relatively conserved among localities. Likewise, voluntary thermal traits remained largely constant along the elevational gradient, with the exception of VTmin, which was lower in the high-elevation population. We also found that the reduction in body size associated with arid environments has competitive consequences. In common garden experiments, small individuals of P. lacertus were competitively subordinate to P. cf. kiziriani, a larger congener that inhabits the higher and more humid portion of the distributional limit of P. lacertus. Conversely, large individuals of P. lacertus were competitively dominant over P. cf. kiziriani. Overall, these results suggest the existence of an evolutionary trade-off, in which the small phenotype may favor persistence in arid environments, but at the cost of reduced competitive ability in contact zones with larger congeners, thereby limiting the expansion of its distributional range. Consequently, the distribution limits of P. lacertus may not be determined solely by direct climatic constraints, but rather by the interaction among local adaptation, evolutionary trade-offs, and biotic interactions.
Description
Tesis presentada para optar al grado de Doctor/a en Sistemática y Biodiversidad.
Keywords
Liolaemus, Morfología animal, Animales Variación, Biodiversidad