Body size, mating system, and ecology interact to shape behaviour and cognition in two syntopic pairs of poeciliid fish
This study compares female behaviour and cognition across poeciliid fish with contrasting male mating systems. Using two syntopic species pairs from Texas and Ecuador, the authors measured exploration, shyness, social motivation and cognitive flexibility. Although species differed by mating system, patterns varied by location, and body size and ecology explained more variation than mating system alone. All‑coercive taxa were more exploratory and socially motivated, with cognitive flexibility differing between regions. These results show that mating system cannot fully account for species‑level behavioural and cognitive differences, highlighting ecological factors such as predation regime.
Subject Tags
- Wildlife
- Biodiversity
Abstract
Female traits often covary with male mating tactics. In single-tactic mating systems, males show a restricted range of phenotypes. In contrast, in mixed-tactic species, males vary in behaviour, size and coloration. The consequences of such differences in mating system for female behaviour and cognition are poorly understood. Poeciliid fish are an excellent clade for addressing this question: males of some species have exclusively forced mating (all-coercive), whereas others (mixed-tactic) also display or defend territories. We compared exploration, shyness, social motivation and cognitive flexibility in two syntopic species pairs: all-coercive Gambusia affinis and mixed-tactic Poecilia latipinna (Texas), and all-coercive Pseudopoecilia fria and mixed-tactic Poecilia gilli (Ecuador). Species differed by mating system in social motivation, exploration and inhibitory control at each location. However, directionality diverged from studies in predator-free conditions. All-coercive taxa were more exploratory and socially motivated in both pairs and more cognitively flexible in the Ecuadorian pair. Relationships between shyness, mating system and body size contrasted between the locations, implicating ecology. General linear models revealed size and location to supersede mating system in explaining trait variation. We show that mating system alone cannot explain species-level variation in female behaviour and cognition, and we discuss factors, such as predation regime, that might also shape traits.
Citation
Inman, C., Yeager, J., Jimenez-Prado, P., & Cummings, M. (2025). Body size, mating system, and ecology interact to shape behaviour and cognition in two syntopic pairs of poeciliid fish. Biological Journal of the Linnean Society, 146(3), blaf095. https://doi.org/10.1093/biolinnean/blaf095
TNC Authors
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Pedro Jiménez-Prado
Freshwater Conservation Scientist
The Nature Conservancy
Email: pedro.jimenez@tnc.org