The role of ancestral monogamy and climate in the evolution of sociality in hystricognath rodents.
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Date
2025
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Universidad de Concepción
Abstract
La evolución de la sociabilidad en animales ha sido un tema central en la sociobiología y la ecología evolutiva. La sociabilidad se define típicamente como la vida en grupo que incluye una amplia gama de formas de organización social, donde individuos animales, invertebrados y vertebrados, pasan parte o toda su vida en asociación con individuos coespecíficos, siendo la eusocialidad, el nivel más avanzado de organización social. En vertebrados, la eusocialidad es excepcionalmente rara y solo ha sido documentada en dos especies de la familia Bathyergidae (Rodentia). Diversas hipótesis han sido propuestas para explicar la transición hacia sistemas sociales. Entre ellas, la hipótesis de la monogamia de por vida postula que la monogamia aumenta la relación genética entre los miembros de un grupo, favoreciendo la cooperación y facilitando la evolución de la eusocialidad. Paralelamente, la hipótesis de las restricciones ecológicas sugiere que factores ambientales, como la aridez, pueden modular la sociabilidad al limitar la dispersión individual y promover la formación de grupos. Los roedores, debido a su diversidad social y amplia distribución, representan un modelo ideal para estudiar estos procesos. En esta tesis, evaluamos estos dos mecanismos en roedores mediante análisis filogenéticos comparativos. En primer lugar, examinamos la evolución de la monogamia en Bathyergidae para evaluar su papel en la transición hacia la eusocialidad. Utilizando reconstrucciones de estados ancestrales y modelos de correlación evolutiva, nuestros resultados indican que la monogamia fue la condición ancestral en especies sociales y eusociales. Sin embargo, no encontramos evidencia de que la monogamia haya sido el factor causal en la evolución de la eusocialidad en este grupo. En segundo lugar, investigamos la relación entre la aridez y la sociabilidad en roedores del infraorden Hystricognathi. Estimamos el tiempo de divergencia de este grupo y caracterizamos las condiciones ambientales de su distribución. No encontramos una asociación significativa entre el índice de aridez y la sociabilidad, lo que sugiere que otros factores ecológicos, como la distribución de recursos y la presión de depredación, podrían ser más relevantes en la evolución de los sistemas sociales. Estos hallazgos aportan nuevas perspectivas sobre los impulsores de la evolución de la sociabilidad en roedores y resaltan la importancia de un enfoque multifactorial que integre historia evolutiva, relaciones filogenéticas y condiciones ecológicas para comprender la diversificación de los sistemas sociales en mamíferos.
The evolution of sociality in animals has been a central topic in sociobiology and evolutionary ecology. Sociality is typically defined as group living, encompassing a wide range of social organization forms in which animal individuals, both invertebrates and vertebrates, spend part or all of their lives associating with conspecifics, with eusociality being the most advanced level of social organization. Among vertebrates, eusociality is exceptionally rare and has only been documented in two species of the Bathyergidae family (Rodentia). Various hypotheses have been proposed to explain the transition to social systems. Among them, the lifetime monogamy hypothesis posits that monogamy increases genetic relatedness among group members, promoting cooperation and facilitating the evolution of eusociality. In parallel, the ecological constraints hypothesis suggests that environmental factors, such as aridity, can shape sociality by limiting individual dispersal and promoting group formation. Due to their social diversity and broad distribution, rodents represent an ideal model for studying these processes. In this thesis, we evaluate these two mechanisms in rodents through phylogenetic comparative analyses. First, we examine the evolution of monogamy in Bathyergidae to assess its role in the transition to eusociality. Using ancestral state reconstructions and evolutionary correlation models, our results indicate that monogamy was the ancestral condition in both social and eusocial species. However, we found no evidence that monogamy was the causal factor in the evolution of eusociality in this group. Second, we investigate the relationship between aridity and sociality in rodents of the infraorder Hystricognathi. We estimate the divergence time of this group and characterize the environmental conditions of its distribution. We do not find a significant association between the aridity index and sociality, suggesting that other ecological factors, such as resource distribution and predation pressure, may be more relevant in the evolution of social systems. These findings provide new insights into the drivers of social evolution in rodents and highlight the importance of a multifactorial approach integrating evolutionary history, phylogenetic relationships, and ecological conditions to understand the diversification of social systems in mammals.
The evolution of sociality in animals has been a central topic in sociobiology and evolutionary ecology. Sociality is typically defined as group living, encompassing a wide range of social organization forms in which animal individuals, both invertebrates and vertebrates, spend part or all of their lives associating with conspecifics, with eusociality being the most advanced level of social organization. Among vertebrates, eusociality is exceptionally rare and has only been documented in two species of the Bathyergidae family (Rodentia). Various hypotheses have been proposed to explain the transition to social systems. Among them, the lifetime monogamy hypothesis posits that monogamy increases genetic relatedness among group members, promoting cooperation and facilitating the evolution of eusociality. In parallel, the ecological constraints hypothesis suggests that environmental factors, such as aridity, can shape sociality by limiting individual dispersal and promoting group formation. Due to their social diversity and broad distribution, rodents represent an ideal model for studying these processes. In this thesis, we evaluate these two mechanisms in rodents through phylogenetic comparative analyses. First, we examine the evolution of monogamy in Bathyergidae to assess its role in the transition to eusociality. Using ancestral state reconstructions and evolutionary correlation models, our results indicate that monogamy was the ancestral condition in both social and eusocial species. However, we found no evidence that monogamy was the causal factor in the evolution of eusociality in this group. Second, we investigate the relationship between aridity and sociality in rodents of the infraorder Hystricognathi. We estimate the divergence time of this group and characterize the environmental conditions of its distribution. We do not find a significant association between the aridity index and sociality, suggesting that other ecological factors, such as resource distribution and predation pressure, may be more relevant in the evolution of social systems. These findings provide new insights into the drivers of social evolution in rodents and highlight the importance of a multifactorial approach integrating evolutionary history, phylogenetic relationships, and ecological conditions to understand the diversification of social systems in mammals.
Description
Tesis presentada para optar al grado de Doctor/a en Sistemática y Biodiversidad.
Keywords
Monogenismo y poligenismo, Evolución, Roedores