What might best explain why anoles on the island of Puerto Rico evolved in different niches of the forest?

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journal article

The Nature of Niche Expansion in West Indian Anolis Lizards II: Evolutionary Components

Evolution

Vol. 30, No. 4 (Dec., 1976)

, pp. 677-692 (16 pages)

Published By: Society for the Study of Evolution

//doi.org/10.2307/2407809

//www.jstor.org/stable/2407809

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Abstract

To determine what evolutionary strategies are involved in niche expansion in West Indian Anolis lizards, the evolution of toe lamellae, dorsal scales and head length were compared among populations known to have different niche widths. The divergence in dorsal scale size, as well as allelic frequencies between forest and open populations suggests that ecotypic variation is a component of habitat expansion in anoles. Within a given habitat, lamellae and dorsal scales showed no tendency toward increased variation in populations having broader niches. Although head length variation was strongly correlated with the width of the food niche in adult male sagrei populations, this tendency was interpreted as a direct consequence of the way lizards grow and the effects of sampling over a range of different size classes. Thus, within-habitat niche expansion does not entail diversifying selection for specialized phenotypes and associated increases in adaptive variation. Rather, the evolutionary component involves selection for a compromise morphology capable of exploiting a variety of perch sites, thermally diverse conditions and an optimal range of prey sizes. These results are viewed as a direct consequence of territoriality which implies fine-grained resource utilization by members of the population and generates phenotypic convergence rather than divergence.

Journal Information

Evolution, published for the Society for the Study of Evolution, is the premier publication devoted to the study of organic evolution and the integration of the various fields of science concerned with evolution. The journal presents significant and original results that extend our understanding of evolutionary phenomena and processes.

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How did the anole lizards on these islands become different species?

One hypothesis is that each type of anole evolved on one of the islands and then migrated to the other islands, where they found similar habitats; over time they speciated and maintained the same body type.

Why have different lizard species evolved to occupy the various niches on an island?

Jonathan Losos said, why have different lizard species evolved to occupy different parts of the habitats? Answer: To minimize competition for food and other resources between different species.

How were the anoles adapted to their environment?

Anoles are renowned for their adaptation to different habitats. One particularly well-documented and ubiquitous axis of adaptation involves the length of the hindlimbs. Both among and within species, lizards that use broader surfaces have longer legs.

How did anole lizards evolve?

Note the lizard's toe pads. Over just 20 generations in 15 years the green anoles evolved larger toe pads equipped with more sticky scales to allow for better climbing (photo 2). The change came after the invasive brown anoles (photo 3) forced them from their ground-level habitat into the trees in order to survive.

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