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Carabidae on Tropical Islands, Especially the West Indies

P. J. Darlington, Jr.
Biotropica
Vol. 2, No. 1 (Jun., 1970), pp. 7-15
DOI: 10.2307/2989782
Stable URL: http://www.jstor.org/stable/2989782
Page Count: 9
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Carabidae on Tropical Islands, Especially the West Indies
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Abstract

Carabid beetles that have reached the Greater Antilles are all small (or at least not very large) and winged. The lowland, Central American source fauna of Carabidae also apparently consists chiefly of small, winged species. Factors favoring small size and possession of wings apparently operated on the mainland before dispersal to the islands. Selection in favor of carabids living in waterside habitats apparently has occurred during dispersal. This is an example of an apparent rule: that plants and animals in unstable or marginal habitats and not members of complex communities are most likely to disperse into new places. Carabidae that have reached the Greater Antilles (and New Guinea) have usually not evolved strikingly at low altitudes, although some speciation has occurred and some ecologic shifting, notably from waterside habitats onto the floor of rain forest. However, on the higher mountains on these and other tropical islands strikingly differentiated faunules have evolved characterized by extreme reduction in number of species and by wing atrophy. This is apparently not a result of exposure on mountains, for the Carabidae concerned live in dense wind-free cloud forest. Rather, existence in very small but relatively favorable, stable areas probably modifies population structures and reverses the usefulness of wings and flight. Three actual cases are described on islands of the West Indies illustrating the complexities that underlie the main pattern of dispersal and evolution. A set of "equilibrium models" of ecologic fractions of a carabid fauna, with arrows indicating ecologic shifts, may show what is actually happening on islands like the Greater Antilles and New Guinea.

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