Mammals as a Key to Evolutionary Theory

Abstract

Mammalogy provides exceptionally fertile grounds for advancing evolutionary theory, be~ cause its data base spans from diverse researches on living forms to a rich fossil record. I illustrate this by integrating interdisciplinary evidence and hypotheses in the habitat theory, including: 1) the context of paleoclimatic changes, and how species' distributions responded to them; 2) geographical biases in turnover rates of species; 3) the turnover-pulse hypothesis; 4) breadth of resource use as a cause of phylogenetic turnover rates. Preliminary tests using the late Neogene records of the Americas and Africa suggest that major aspects of the Great American Interchange have parallels in the African record, as predicted by the habitat theory. Comparable forces may have operated in both cases. The habitat theory ofthe Great American Interchange differs from the traditional emphasis on the effects of interspecific competition.

The Geography of Evolution and the Evolution of Geography

“…Some of these species would experience such profound range reductions that they would go extinct (the Turnover phase of her hypothesis). However, for those populations that persisted and stayed isolated in these refugia for long enough, they would diverge and eventually speciate (Vrba 1980(Vrba , 1985(Vrba , 1992) (the Pulse phase of her hypothesis). In this manner, several new species in the same region would evolve at roughly the same time.…”

“…Another major innovation in macroevolutionary theory was Elisabeth Vrba's development of the Turnover Pulse Hypothesis (Vrba 1980(Vrba , 1985(Vrba , 1992. Eldredge (1971) and Eldredge and Gould (1972) in their formulation of punctuated equilibria did rely on allopatric speciation, but they specifically focused on Mayr's (1942Mayr's ( , 1963) discussion of the concept whereby geographic isolation occurred when a population of a species dispersed over a preexisting geographic barrier.…”

“…However, when allopatric speciation transpires in this manner, it usually will involve only a single species at a time; and further, whether or not speciation happens depends to a major extent on the individual ecological characteristics of the organisms in the species. Vrba's (1980Vrba's ( , 1985Vrba's ( , 1992 innovation with the Turnover Pulse Hypothesis was that she recognized the significance of the fact that during intervals of climate change, the geographic ranges of many species would be affected simultaneously. She specifically focused on Neogene tropical mammal species that during times of warmth might have broad geographic ranges.…”

“…Thus, vicariance biogeography provides a means of directly considering and testing the relative roles that geology and climate play as processes that motivate macroevolution. Vrba (1980Vrba ( , 1985Vrba ( , 1992 essentially extended vicariance biogeography directly into the realm of evolutionary theory by focusing on the significant role that climate change plays in causing evolution via the mechanisms of geographic isolation and allopatric speciation.…”

Adaptação do Comportamento Animal e Mundos Emergentes

“…Nesta perspectiva, as linhagens que desaparecem seriam aquelas cujo polimorfismo genético seria limitado demais para permitir adaptar-se aos problemas postos pelo meio ambiente (van Valen, 1973). Mas devemos notar o fato de que um grande número de linhagens de organismos persistem e têm conservado uma mesma morfologia apesar das modificações ocorridas no globo (Gould & Eldredge, 1993;Raup, 1992;Vrba, 1992 Dobzhansky (1973), que dizia que "nada tem sentido na biologia salvo à luz da evolução", em um "nada tem sentido no meio ambiente salvo à luz de um sistema vivo". Os sons, os odores são manifestações fenomenais que não existem em si, mas relativamente a um sujeito cognitivo que vai corporificá-las nas situações vividas.…”