title: The number of competitor species is unlinked to sexual dimorphism.
abstract: Sexual size dimorphism (SSD) can allow males and females of the same species to specialize on different sized food items and therefore minimize intraspecific competition. Interspecific competition, however, is thought to limit sexual dimorphism, as larger competitors in the community will prevent the larger sex from evolving larger size, and smaller species may prevent the smaller sex from becoming even smaller. We tested this prediction using data on the sexual size dimorphism of lizards, and mammalian carnivores, on islands world-wide. Because insular communities are depauperate, and guilds are species-poor, it is often assumed that enhanced sexual size dimorphism is common on islands. The intensity of interspecific competition, hindering enhanced dimorphism, is thought to increase with competitor richness. We tested whether intraspecific sexual size dimorphism of mammalian carnivores and lizards decreases with increasing island species richness. We further computed the average sexual dimorphism of species on islands and tested whether species-rich islands are inhabited by relatively monomorphic species. Within families and guilds across carnivores and lizards, and with both intraspecific and interspecific approaches, we consistently failed to find support for the notion that species-poor islands harbour more sexually dimorphic individuals or species. We conclude that either interspecific competition does not affect the sexual size dimorphism of insular lizards and carnivores (i.e. character displacement and species sorting are rare in these taxa), or that the number of species in an assemblage or guild is a poor proxy for the intensity of interspecific competition in insular assemblages.
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
authors.forename: Shai
authors.initials: S
authors.lastname: Meiri
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Kadison
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
authors.forename: Maria
authors.initials: M
authors.lastname: Novosolov
authors.affiliation: Section of Zoology and Marine Biology, Department of Biology, University of Athens, Panepistimioupolis, Ilissia, Athens, 157-84, Greece.
authors.forename: Panayiotis
authors.initials: P
authors.lastname: Pafilis
authors.affiliation: School of Natural Resources and Environment, University of Michigan, Ann Arbor, Ann Arbor, MI, 48109, USA.
authors.forename: Johannes
authors.initials: J
authors.lastname: Foufopoulos
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Itescu
authors.affiliation: Dipartimento di Scienze della Terra, dell'Ambiente e delle Risorse, Università Federico II, L.go San Marcellino 10, Naples, 80138, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Raia
authors.affiliation: School of Life Sciences, University of Lincoln, Riseholme Park, Lincoln, LN2 2LG, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pincheira-Donoso
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D049628:Body Size; D002335:Carnivora / Q000502:physiology*; D062312:Islands; D008116:Lizards / Q000502:physiology*; D012727:Sex Characteristics
keywords: Carnivora; character displacement; interspecific competition; intraspecific competition; islands; lizards; species sorting