Strength of Sexual Selection and Sex Roles Vary between Social Groups in a Coral Reef Cardinalfish
Rueger, Theresa, MacDonald, Chancey, Harrison, Hugo B., Gardiner, Naomi P., Jones, Geoffrey P., and Mills, Suzanne C. (2024) Strength of Sexual Selection and Sex Roles Vary between Social Groups in a Coral Reef Cardinalfish. American Naturalist, 204 (3).
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Abstract
The strength and direction of sexual selection can vary among populations. However, spatial variability is rarely explored at the level of the social group. Here we investigate sexual selection and sex roles in the paternally mouthbrooding, socially monogamous, and site-attached pajama cardinalfish, Sphaeramia nematoptera. Females were larger and more aggressive and had a longer dorsal fin filament, indicating reversed sex roles. At the scale of social groups, we show that the Bateman gradient and reproductive variance depend on the sex ratio and size of groups. In small and medium-sized groups with balanced or male-biased sex ratios, Bateman gradients were steeper for females, whereas gradients were equally steep for both sexes in large groups or when the sex ratio was female biased. For both sexes, reproductive variance increased with group size and with a higher male-to-female sex ratio. In S. nematoptera, mating opportunities out-side the socially monogamous pair appear to impact sexual selection. We conclude that strength and direction of sexual selection can be masked by social dynamics in group-living species when considering only population and large-scale demographic processes.
| Item ID: | 84316 |
|---|---|
| Item Type: | Article (Research - C1) |
| ISSN: | 1537-5323 |
| Keywords: | Bateman gradients, reproductive skew, reproductive variance, reversed sex roles, sexual dimorphism, sexual selection |
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| Copyright Information: | © 2024 The University of Chicago. All rights reserved. Published by The University of Chicago Press for The American Society of Naturalists. |
| Date Deposited: | 11 Dec 2024 22:59 |
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