L. (Lisheng) Zhang

PhD thesis: The implications of adult sex ratios on evolutionary dynamics of dung beetles - Insights from Onthophagus taurus (2023)

The Adult Sex Ratio (ASR), defining the proportion of adult males to females in a population, is recognized as a cardinal determinant governing ecological interactions and evolutionary trajectories. This thesis delves into the pivotal role of Adult Sex Ratio in ecological and evolutionary processes, leveraging innovative methodologies to elucidate the multidimensional impacts of ASR on behavioural dynamics and breeding systems, primarily using the dung beetle, Onthophagus taurus, as a model organism. The comprehensive analysis reveals that ASR significantly influences contest and courtship competition intensity, correlating with male reproductive success without altering parental investment or female reproductive outcome. It additionally provides novel insights, suggesting that ASR does not directionally impact individual personalities, with social experience emerging as a more determinant factor in shaping behaviours like righting and aggressiveness, but not boldness and foraging behaviours. Further investigations into parental ASR and offspring development indicate no discernible impacts on either developmental outcomes or parental care within a single generational cycle, challenging prevailing hypotheses. Cumulatively, the findings spotlight the necessity for an expanded ASR research framework, advocating for broader applicability in future studies, both in species range and research dimensions, while emphasizing the integration of advanced biotechnologies to unearth intricate ASR-related dynamics. This thesis contributes valuable perspectives to behavioural and evolutionary ecology, underlining the subtle complexities and far-reaching implications of ASR in shaping ecological interactions and evolutionary trajectories.