. Annual report. Harvard University. Museum of Comparative Zoology. Physical Evolution Keeps Pace with Ecological Opportunity. Adaptive radiation—where a single ancestral species gives rise to many descendants, each adapted to a different part of the environment—is possibly the single most important source of biodiversity in the world. One of the best-studied examples of adaptive radiation is the Anolis lizards, which arrived in the islands of the Caribbean around 40 million years ago from South America and evolved into numerous species of dramatically differing body sizes and limb lengths. In
. Annual report. Harvard University. Museum of Comparative Zoology. Physical Evolution Keeps Pace with Ecological Opportunity. Adaptive radiation—where a single ancestral species gives rise to many descendants, each adapted to a different part of the environment—is possibly the single most important source of biodiversity in the world. One of the best-studied examples of adaptive radiation is the Anolis lizards, which arrived in the islands of the Caribbean around 40 million years ago from South America and evolved into numerous species of dramatically differing body sizes and limb lengths. In theory, ecological opportunity—the availability of resources, such as food and territory, and the amount of competition for those resources—is the primary factor regulating the pace of species diversification, so the rate of diversification should slow as opportunity declines. However, does this theory also hold true for the diversification of body size and shape? To investigate the relationship between ecological opportunity and morphological evolution, D. Luke Mahler, Jonathan B. Losos and colleagues employed genetic methods and data from body measurements of around 100 species of Caribbean anoles from Cuba, Hispaniola, Jamaica and Puerto Rico. They found that the earliest species with the greatest resources and little or no competition developed the widest variety of body types and sizes—from foot-long giants that travel the treetops to slender lizards that live in bushes. But as the number of Anolis species increased and their ecological niches became smaller, the resulting adaptations in body type slowed and became more subde. The research was published in Evolution. Mahler DL, Revell LJ, Glor RE, LososJB (2010) Ecological oppormnity and the rate of morphological evolution in the diversification of Greater Antillean anoles. Evolution 64:2731-2745. 16 Museum of Comparative Zoology. Please note that these images are extracted from scanned page images that may have
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