The Nature of Niche Expansion in West Indian Anolis Lizards I: Ecological Consequences of Reduced Competition

Ecological Opportunity in Adaptive Radiation of Galápagos Endemic Land Snails

“…When a species is released from interspecific competition by colonizing a vacant adaptive zone, competition among conspecific individuals for limiting resources is predicted to promote divergence in phenotype and resource use, leading to an increase in intraspecific phenotypic variation (Van Valen 1965;Roughgarden 1972;Lister 1976;Bolnick 2004;Svanback and Bolnick 2007). As the adaptive radiation proceeds and the lineage diversifies into multiple species, the total range of resources used expands, and interspecific competition between newly formed species promotes phenotypic divergence among species but constrains it within species (Arthur 1987).…”

Evolutionary consequences of ecological release in CaribbeanAnolislizards

“…Among trunk-ground derivatives, two of the morphologicallygeneralized taxa, A. scriptus (Laska, 1970) and^l. sagrei nelsoni (Lister, 1976a), appear to be generalized in structural habitat use. The situation is less clear for other trunkground derivatives; published reports are contradictory on whether A. monensis (Gorman & Stamm, 1975;Lister, 1976a) or A. sagrei luteosignifer (Lister, 1976a; this study) are more ecologically generalized than their relatives from larger islands with more complex faunas.…”

“…sagrei nelsoni (Lister, 1976a), appear to be generalized in structural habitat use. The situation is less clear for other trunkground derivatives; published reports are contradictory on whether A. monensis (Gorman & Stamm, 1975;Lister, 1976a) or A. sagrei luteosignifer (Lister, 1976a; this study) are more ecologically generalized than their relatives from larger islands with more complex faunas. Among trunk-crown descendants, the literature also suggests that A. conspersus has unusually broad habitat use (Lister, 1976a), but our data did not indicate that its habitat use, nor that of A. camlinensis brunneus or A. maynardi, is any broader than that of trunk-crown anoles in the Greater Antilles.…”

“…Evolutionary biologists have proposed two theories about the evolutionary outcome of such situations. On one hand, the avauabuity of resources and lack of competitors may lead to 'ecological release' as organisms expand their resource use to incorporate resources they do not normally use in their ancestral environment (Lister, 1976a;Schoener, 1986). Over evolutionary time, this expansion may lead to the evolution of a generalist capable of using a broad range of resources, possibly at the cost of lack of specialization to any particular resource (Lister, 1976b).…”

Sexual dimorphism in Trachylepis vittata (Olivier, 1804) (Sauria: Scincidae) in the Zagros Mountains, western Iran

“…Selection favoring intersexual differences in body shape might result from differences between the sexes in ecology (niche partitioning between the sexes), behavior (territorial or mate choice behavior), or reproduction (physiological or anatomical differences related to different reproductive costs or roles [Darwin, 1859[Darwin, , 1871). Sex differences in ecology (food and/or habitat) associated with shape dimorphism are known from many reptiles (e.g., Schoener, 1967Schoener, , 1968Schoener and Gorman, 1968;Lister, 1970;Schoener et al, 1982;Hebrard and Madsen, 1984;Powell and Russell, 1984;Shine, 1991;Vitt et al, 1996). Behavior can influence dimorphism by the operation of sexual selection, which may result in exaggeration of body proportions in one sex, usually males (Butler and Losos, 2001).…”