Convergencia incompleta en Alsodidae (Anura: Alsodes Bell 1843) acuáticos de alta montaña: Análisis mediante microtomografía computarizada y métodos comparados filogenéticos
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Date
2024
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Universidad de Concepción
Abstract
La fascinación por la diversidad biológica y cómo las especies se han adaptado a sus entornos ha llevado a explorar fenómenos como la convergencia evolutiva; proceso en el cual diferentes linajes han evolucionado de manera independiente, desarrollando similitudes morfológicas como respuesta a presiones selectivas similares en distintas partes geográficas. Los anuros, con su amplia diversidad y adaptaciones morfológicas específicas, son un grupo ideal para estudiar estos mecanismos. En particular, el género Alsodes, representativo de la biodiversidad de anfibios en Chile, incluye especies adaptadas tanto a bosques templados como a ambientes acuáticos altoandinos. De esta forma, las presiones selectivas diferenciales de estos ambientes, como la disponibilidad de presas, influiría en los mecanismos de alimentación promoviendo evolución de estructuras craneales y rasgos como la orientación ocular que favorecerían la adaptación a estos ambientes. La predicción de esta hipótesis sería la convergencia evolutiva en estos rasgos entre las especies acuáticas altoandinas Alsodes montanus y Alsodes pehuenche. Para evaluar la principal predicción de la hipótesis evolutiva, se actualizó y calibró la hipótesis filogenética de Alsodidae, incluyendo a A. montanus por primera vez. Se midieron características morfológicas usando fotografías dorsales de la cabeza y microtomografía computarizada de alta resolución para analizar la orientación ocular y la forma del módulo integrado del suspensorio con imágenes 3D, respectivamente. La convergencia evolutiva entre especies acuáticas altoandinas se evaluó mediante métodos comparados filogenéticos y se modificó la métrica C1 de Stayton basada en patrones. De esta forma, se determinó una convergencia incompleta entre las especies acuáticas altoandinas, y las adaptaciones sugieren un mecanismo de alimentación por succión inercial, al menos en A. montanus. Finalmente, aunque A. montanus y Alsodes pehuenche presentan rasgos similares, este último se encuentra influenciado tanto por la relación ancestro-descendencia (régimen evolutivo terrestre) como por una colonización más reciente de los ambientes acuáticos extremos altoandinos, lo que indica adaptaciones morfológicas específicas para la supervivencia en estos hábitats.
The fascination with biological diversity and how species has adapted to their environments has led to the exploration of phenomena such as evolutionary convergence; a process in which different lineages have evolved independently, developing morphological similarities as a response to similar selective pressures in different geographical areas. Anurans, with their wide diversity and specific morphological adaptations, are an ideal group to study these mechanisms. In particular, the genus Alsodes, representative of amphibian biodiversity in Chile, includes species adapted to both temperate forests and high Andean aquatic environments. Thus, the differential selective pressures of these environments, such as prey availability, would influence feeding mechanisms promoting the evolution of cranial structures and traits such as eye orientation that would favor adaptation to these environments. The prediction of this hypothesis would be the evolutionary convergence of these traits between the high Andean aquatic species Alsodes montanus and Alsodes pehuenche. To evaluate the main prediction of the evolutionary hypothesis, the phylogenetic hypothesis of Alsodidae was updated and calibrated, including A. montanus for the first time. Morphological characteristics were measured using dorsal photographs of the head and high-resolution computed microtomography to analyze eye orientation and the shape of the integrated suspensorium module with 3D images, respectively. The evolutionary convergence between high Andean aquatic species was assessed using comparative phylogenetic methods, and Stayton's C1 metric was modified based on patterns. In this way, incomplete convergence was determined between the high Andean aquatic species, and the adaptations suggest a mechanism of inertial suction feeding, at least in A. montanus. Finally, although A. montanus and Alsodes pehuenche present similar traits, the latter is influenced both by the ancestor-descendant relationship (terrestrial evolutionary regime) and by a more recent colonization of the extreme high Andean aquatic environments, indicating specific morphological adaptations for survival in these habitats.
The fascination with biological diversity and how species has adapted to their environments has led to the exploration of phenomena such as evolutionary convergence; a process in which different lineages have evolved independently, developing morphological similarities as a response to similar selective pressures in different geographical areas. Anurans, with their wide diversity and specific morphological adaptations, are an ideal group to study these mechanisms. In particular, the genus Alsodes, representative of amphibian biodiversity in Chile, includes species adapted to both temperate forests and high Andean aquatic environments. Thus, the differential selective pressures of these environments, such as prey availability, would influence feeding mechanisms promoting the evolution of cranial structures and traits such as eye orientation that would favor adaptation to these environments. The prediction of this hypothesis would be the evolutionary convergence of these traits between the high Andean aquatic species Alsodes montanus and Alsodes pehuenche. To evaluate the main prediction of the evolutionary hypothesis, the phylogenetic hypothesis of Alsodidae was updated and calibrated, including A. montanus for the first time. Morphological characteristics were measured using dorsal photographs of the head and high-resolution computed microtomography to analyze eye orientation and the shape of the integrated suspensorium module with 3D images, respectively. The evolutionary convergence between high Andean aquatic species was assessed using comparative phylogenetic methods, and Stayton's C1 metric was modified based on patterns. In this way, incomplete convergence was determined between the high Andean aquatic species, and the adaptations suggest a mechanism of inertial suction feeding, at least in A. montanus. Finally, although A. montanus and Alsodes pehuenche present similar traits, the latter is influenced both by the ancestor-descendant relationship (terrestrial evolutionary regime) and by a more recent colonization of the extreme high Andean aquatic environments, indicating specific morphological adaptations for survival in these habitats.
Description
Tesis para optar al grado académico de Magíster en Ciencias con Mención en Zoología
Keywords
Filogenética molecular, Anuros, Anfibios Chile