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Related Experiment Video

Updated: Sep 14, 2025

Modeling the Size Spectrum for Macroinvertebrates and Fishes in Stream Ecosystems

Modeling the Size Spectrum for Macroinvertebrates and Fishes in Stream Ecosystems

Published on: July 30, 2019

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

Joel H Gayford^1,2, Scott G Seamone³, Duncan J Irschick⁴

¹College of Science and Engineering, James Cook University Townsville Queensland Australia.

Ecology and Evolution

|July 23, 2025

Summary

This summary is machine-generated.

Sexual size dimorphism (SSD) in rays shows subtle differences from sharks, suggesting weaker selection for extreme size differences. Further research is needed to understand the evolutionary drivers in elasmobranchs.

Keywords:

Rensch's rule allometry batoid fecundity selection reproductive mode scaling sexual selection shark

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Published on: May 7, 2016

Area of Science:

Marine Biology
Evolutionary Biology
Ichthyology

Background:

Sexual size dimorphism (SSD) is common in animals but its evolutionary drivers are debated.
Elasmobranchii (sharks and rays) exhibit varied SSD, potentially linked to reproductive strategies.
Previous research on elasmobranch SSD has largely ignored batoids (rays).

Purpose of the Study:

To quantify SSD variation across 187 batoid species.
To investigate ecological and evolutionary drivers of SSD in batoids.
To compare SSD patterns and drivers between batoids and sharks.

Main Methods:

Analysis of published size records (total length, disc width) for 187 batoid species.
Comparative phylogenetic analysis to test for ecological and evolutionary drivers of SSD.
Statistical examination of interspecific SSD variation.

Main Results:

Batoid SSD patterns superficially resemble those of sharks.
Subtle differences in ecological signals and trait evolution were observed between batoids and sharks.
Selection for substantial male-biased and female-biased SSD appears weaker in batoids than in sharks.

Conclusions:

Batoids exhibit unique patterns of SSD compared to sharks, indicating potentially different evolutionary pressures.
Weaker selection for extreme SSD in batoids may relate to variations in fecundity selection.
Future studies should focus on sexual and fecundity selection to fully elucidate SSD evolution in elasmobranchs.