Evolutionary Biology

, Volume 42, Issue 2, pp 223–234

Disentangling the Size and Shape Components of Sexual Dimorphism

Research Article

DOI: 10.1007/s11692-015-9313-z

Cite this article as:
Cheng, RC. & Kuntner, M. Evol Biol (2015) 42: 223. doi:10.1007/s11692-015-9313-z

Abstract

Many organisms are sexually dimorphic, reflecting sex-specific selection pressures. But although sexual dimorphism may consist of different variables from size to shape and physiology, most research emphasizes a single aspect of sexual dimorphism, notably size, without specifying its components and their relationship. Among terrestrial animals, spiders exhibit most extreme sex-specific differences in size and abdominal shape, and therefore represent ideal models to address this question. Here, we dissect sexual dimorphism in spiders at two phylogenetic hierarchical levels. At the species level, we employ comparative phylogenetic tests to explore the association between sexual shape dimorphism (SShD) and sexual size dimorphism (SSD) in the orbweb clade Argiopinae. At the genus level, we then explore such patterns on a phylogeny of orb weavers (Araneoidea). Female argiopines had more diverse abdominal morphotypes than the males and the abdominal shape evolution was only poorly correlated between the sexes. Phylogenetic and comparative data suggested that evolution of SShD in argiopines was related to geographic history, but that sexually shape monomorphic cases arose through selection for male size, perhaps acting against fecundity selection. While in argiopines there was no clear association between SShD and SSD, we detected a significant correlation in all orb weavers at the genus level. The shape and the size components of sexual dimorphism may thus respond independently to selection pressures, but at certain phylogenetic levels SSD may be a prerequisite for SShD. Research on other animal groups is needed to establish whether the here detected patterns on spiders are general.

Keywords

Sexual shape dimorphism Sexual size dimorphism Abdominal shape Sexual selection Intraspecific niche divergence Spiders 

Supplementary material

11692_2015_9313_MOESM1_ESM.txt (182 kb)
Supplementary material 1 (TXT 181 kb)
11692_2015_9313_MOESM2_ESM.xlsx (20 kb)
The size measurement, body shape, SSD and SShD of argiopine spiders. See separate file Tables_S1.xlsx
11692_2015_9313_MOESM3_ESM.xlsx (20 kb)
SSD and SShD scores for araneoid spiders with references. See separate file Tables_S2.xlsx

Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.Evolutionary Zoology LaboratoryBiological Institute ZRC SAZULjubljanaSlovenia
  2. 2.Centre for Behavioural Ecology and Evolution, College of Life SciencesHubei UniversityWuhanChina
  3. 3.National Museum of Natural HistorySmithsonian InstitutionWashingtonUSA

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