Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)

ABSTRACT Sexual size dimorphism (SSD) is a widely observed but poorly understood phenomenon in which male and female animals differ in body size (e.g., length or mass). Despite extensive research on the interspecific distribution of SSD across various lineages, the evolutionary drivers behind male‐b...

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Main Authors: Joel H. Gayford, Scott G. Seamone, Duncan J. Irschick, Andrew Chin, Jodie L. Rummer
Format: Article
Language:English
Published: Wiley 2025-07-01
Series:Ecology and Evolution
Subjects:
Online Access:https://doi.org/10.1002/ece3.71858
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author Joel H. Gayford
Scott G. Seamone
Duncan J. Irschick
Andrew Chin
Jodie L. Rummer
author_facet Joel H. Gayford
Scott G. Seamone
Duncan J. Irschick
Andrew Chin
Jodie L. Rummer
author_sort Joel H. Gayford
collection DOAJ
description ABSTRACT Sexual size dimorphism (SSD) is a widely observed but poorly understood phenomenon in which male and female animals differ in body size (e.g., length or mass). Despite extensive research on the interspecific distribution of SSD across various lineages, the evolutionary drivers behind male‐biased and female‐biased SSD remain contentious. In Elasmobranchii (sharks and rays), it is hypothesised that spatiotemporal differences in reproductive effort distribution between oviparous and matrotrophic species underlie variation in the direction and magnitude of SSD. However, existing studies have focused almost exclusively on sharks, overlooking batoids (rays), which comprise over 50% of elasmobranch diversity. In this study, we analysed published size (total length and disc width) records from 187 batoid species to quantify interspecific SSD variation across batoids and tested for ecological and evolutionary drivers of SSD within a comparative phylogenetic framework. Our findings reveal that, although interspecific trends in SSD among batoids superficially mirror those in sharks, subtle differences emerge in ecological signal and modes of trait evolution between the two. These differences suggest that selection for substantial male‐biased and female‐biased SSD in batoids is weaker than in sharks. The underlying reasons for this remain unclear but may involve variation in fecundity selection between batoids and sharks. Further studies quantifying variation in sexual selection and fecundity selection will be essential to fully clarify the adaptive basis of SSD variation within elasmobranchs.
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spelling doaj-art-76cc3a3e90174311a75b6a60c2a987aa2025-08-20T02:46:16ZengWileyEcology and Evolution2045-77582025-07-01157n/an/a10.1002/ece3.71858Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)Joel H. Gayford0Scott G. Seamone1Duncan J. Irschick2Andrew Chin3Jodie L. Rummer4College of Science and Engineering, James Cook University Townsville Queensland AustraliaDepartment of Marine Sciences Bahamas Agriculture and Marine Science Institute San Andros BahamasDepartment of Biology Morrill Science Center, University of Massachusetts Amherst Massachusetts USACollege of Science and Engineering, James Cook University Townsville Queensland AustraliaCollege of Science and Engineering, James Cook University Townsville Queensland AustraliaABSTRACT Sexual size dimorphism (SSD) is a widely observed but poorly understood phenomenon in which male and female animals differ in body size (e.g., length or mass). Despite extensive research on the interspecific distribution of SSD across various lineages, the evolutionary drivers behind male‐biased and female‐biased SSD remain contentious. In Elasmobranchii (sharks and rays), it is hypothesised that spatiotemporal differences in reproductive effort distribution between oviparous and matrotrophic species underlie variation in the direction and magnitude of SSD. However, existing studies have focused almost exclusively on sharks, overlooking batoids (rays), which comprise over 50% of elasmobranch diversity. In this study, we analysed published size (total length and disc width) records from 187 batoid species to quantify interspecific SSD variation across batoids and tested for ecological and evolutionary drivers of SSD within a comparative phylogenetic framework. Our findings reveal that, although interspecific trends in SSD among batoids superficially mirror those in sharks, subtle differences emerge in ecological signal and modes of trait evolution between the two. These differences suggest that selection for substantial male‐biased and female‐biased SSD in batoids is weaker than in sharks. The underlying reasons for this remain unclear but may involve variation in fecundity selection between batoids and sharks. Further studies quantifying variation in sexual selection and fecundity selection will be essential to fully clarify the adaptive basis of SSD variation within elasmobranchs.https://doi.org/10.1002/ece3.71858allometrybatoidfecundity selectionRensch's rulereproductive modescaling
spellingShingle Joel H. Gayford
Scott G. Seamone
Duncan J. Irschick
Andrew Chin
Jodie L. Rummer
Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)
Ecology and Evolution
allometry
batoid
fecundity selection
Rensch's rule
reproductive mode
scaling
title Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)
title_full Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)
title_fullStr Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)
title_full_unstemmed Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)
title_short Sexual Size Dimorphism in Rays and Skates (Elasmobranchii: Batoidea)
title_sort sexual size dimorphism in rays and skates elasmobranchii batoidea
topic allometry
batoid
fecundity selection
Rensch's rule
reproductive mode
scaling
url https://doi.org/10.1002/ece3.71858
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