1. Sexual dimorphism driven by intersexual resource competition: Why is it rare, and where to look for it?
- Author
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Li, Xiang‐Yi, Kokko, Hanna, University of Zurich, and Li, Xiang‐Yi
- Subjects
Male ,0106 biological sciences ,Niche ,ecological character displacement ,Biology ,010603 evolutionary biology ,01 natural sciences ,polymorphism ,Sexual conflict ,10127 Institute of Evolutionary Biology and Environmental Studies ,mating system ,Animals ,Mating ,Research Articles ,Ecosystem ,Ecology, Evolution, Behavior and Systematics ,Ecological niche ,Sex Characteristics ,Reproduction ,010604 marine biology & hydrobiology ,Niche differentiation ,bet‐hedging ecological character displacement intersexual resource competition mating system niche partitioning polymorphism sexual dimorphism ,Mating system ,Biological Evolution ,Sexual dimorphism ,1105 Ecology, Evolution, Behavior and Systematics ,Phenotype ,Evolutionary Ecology ,Evolutionary biology ,intersexual resource competition ,sexual dimorphism ,Sexual selection ,570 Life sciences ,biology ,590 Animals (Zoology) ,niche partitioning ,Female ,Animal Science and Zoology ,bet‐hedging ,1103 Animal Science and Zoology ,Research Article - Abstract
Sexes often differ more obviously in secondary sexual characteristics than in traits that appear naturally selected, despite conceivable benefits to intersexual niche partitioning. Genetic constraints may play a role in limiting sex‐specific niche evolution; however, it is not clear why this limit should apply to naturally selected traits more than those under sexual selection; the latter routinely produces dimorphism. We ask whether ecological factors and/or features of the mating system limit dimorphism in resource use, or conversely, what conditions are the most permissible ones for sexual niche differences.The scale of mating competition and spatial variation in resource availability can help predict sexually dimorphic niches or the lack thereof. We investigate why and when dimorphism might fail to evolve even if genetic covariation between the sexes posed no constraint.Our analytical model incorporates the first aspect of spatial interactions (scale of mating competition). It is followed by simulations that explore broader conditions, including multiple resources with habitat heterogeneity, genetic correlations and non‐Gaussian resource‐use efficiency functions.We recover earlier known conditions for favourable conditions for the evolution of niche partitioning between sexes, such as narrow individual niche and low degrees of genetic constraint. We also show spatial considerations to alter this picture. Sexual niche divergence occurs more readily when local mating groups are small and different resources occur reliably across habitats. Polygyny (medium‐sized or large mating groups) can diminish the prospects for dimorphism even if no genetic constraints are present. Habitat heterogeneity typically also disfavours niche dimorphism but can also lead to polymorphism within a sex, if it is beneficial to specialize to be very competitive in one habitat, even at a cost to performance in the other.Sexual conflict is usually used to explain dimorphic traits or behaviours. Our models highlight that introducing conflict (achieved by switching from monogamy to polygamy) can also be responsible for sexual monomorphism. Under monogamy, males benefit from specializing to consume other resources than what feeds the female best. Polygyny makes males disregard this female benefit, and both sexes compete for the most profitable resource, leading to overlapping niches., Why is sexual dimorphism driven by intersexual resource competition so rare in nature? The authors use a set of models and simulations to answer the question, and identify conditions favorable for the evolution of such ecological inter‐sexual character displacement, including small spatial scales of interaction and reliable co‐presence of different resources.
- Published
- 2021