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Ecological explanations to island gigantism: dietary niche divergence, predation, and size in an endemic lizard

Author:
  • Anna Runemark
  • Kostas Sagonas
  • Erik Svensson
Publishing year: 2015
Language: English
Pages: 2077-2092
Publication/Series: Ecology
Volume: 96
Issue: 8
Document type: Journal article
Publisher: Ecological Society of America

Abstract english

Although rapid evolution of body size on islands has long been known, the ecological mechanisms behind this island phenomenon remain poorly understood. Diet is an important selective pressure for morphological divergence. Here we investigate if selection for novel diets has contributed to the multiple independent cases of island gigantism in the Skyros wall lizard (Podarcis gaigeae) and if diet, predation, or both factors best explain island gigantism. We combined data on body size, shape, bite force, and realized and available diets to address this. Several lines of evidence suggest that diet has contributed to the island gigantism. The larger islet lizards have relatively wider heads and higher bite performance in relation to mainland lizards than would be expected from size differences alone. The proportions of consumed and available hard prey are higher on islets than mainland localities, and lizard body size is significantly correlated with the proportion of hard prey. Furthermore, the main axis of divergence in head shape is significantly correlated with dietary divergence. Finally, a model with only diet and one including diet and predation regime explain body size divergence equally well. Our results suggest that diet is an important ecological factor behind insular body size divergence, but could be consistent with an additional role for predation.

Keywords

  • Evolutionary Biology
  • bite force
  • body shape
  • diet
  • Greece
  • insularity
  • island biogeography
  • island gigantism
  • Lacertidae
  • Podarcis gaigeae
  • population divergence
  • predation
  • Skyros wall lizard

Other

Published
  • ISSN: 0012-9658
erik_svensson
E-mail: erik [dot] svensson [at] biol [dot] lu [dot] se

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Evolutionary ecology

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Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden