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Geometric morphometrics reveals sex-differential shape allometry in a spider
Carmen Fernández-Montraveta1, Jesús Marugán-Lobón2,3
1Departamento de Psicología Biológica y de la Salud, Universidad Autónoma de Madrid, Madrid, Spain.
Peerj
|August 2, 2017
Summary
Sexual dimorphism in spiders often results from male sexual selection. This study reveals size-independent shape differences in the spider *Donacosa merlini*, challenging traditional hypotheses on sexual selection and spider evolution.
Area of Science:
- Evolutionary Biology
- Zoology
- Arachnology
Background:
- Sexual dimorphism (SD) in spiders is commonly attributed to sexual selection favoring larger males.
- Testing hypotheses like male size hyperallometry has been limited by methodological constraints.
Purpose of the Study:
- To investigate sex-differential shape allometry in *Donacosa merlini*, a species with male-biased sexual size dimorphism.
- To explore the origins of sexual shape dimorphism independent of body size.
Main Methods:
- Geometric morphometrics (GMM) was employed to analyze sex-differential shape allometry.
- Shape differences were assessed in relation to body size and size-independent factors.
Main Results:
- Geometric morphometrics revealed previously undetected sex-differential shape allometry.
- Significant sex-related shape differences were found to be size-independent.
- Sexual shape dimorphism impacts relative carapace-to-opisthosoma size and carapace geometry.
Conclusions:
- Size-independent shape differences arise from distinct selection pressures related to reproductive roles and lifestyles.
- Modular variation in body parts contributes to sex differences in shape, reconciling diverse interpretations of spider SD origins.
