Paleophysiographic and paleoenvironmental histories in northern Latin America - Possible impact on modes of speciation


  • Alan Graham Department of Biological Sciences, Kent State University, Kent, Ohio 44242, U.S.A.



Tertiary, Palynology, Palaeoenvironments, Speciation, Northern Latin America


Although land surfaces between central and southern Mexico and northern South America are presently continuous, the area encompasses three zones that have had different physiographic and environmental histories. In central and southern Mexico highlands were present in the Late Cretaceous, and significant physiographic relief and habitat diversity have existed since the Late Tertiary. Continuous land connections existed to the north throughout the Cenozoic, and to the south after about 3.5 Ma, and these connections provided source areas for the immigration and emigration of temperate and tropical elements, as well as introductions throughout the Cenozoic by long-distance dispersal. The region experienced the global climatic cooling of the Late Cenozoic, which was augmented by coastal upwelling with closure of the Panama land bridge. In contrast, central America has never had the extensive high elevations or habitat diversity of central to southern Mexico; the region consisted of islands and peninsulas for most of the Cenozoic with limited access to source areas both to the north and south until about 3.5 Ma; and the impact of Late Cenozoic climatic change was muted, in part, because of the lower latitude, low physiographic relief, and the insular environment. The Amazon Basin of northern South America has had low physiographic relief throughout the Cenozoic, but it is surrounded by the northern Andes that had attained substantial relief and habitat diversity by the Miocene. Biotas in the Amazon Basin experienced some effects of Late Cenozoic climatic change, and these were augmented by fluctuations in the water table resulting from sea-level changes caused by the expansion and contraction of polar glaciers. The effect was the periodic fragmentation of the lowland biota, accompanied by expansion of drier-habitat communities during intervals of cool glacial climates and lowered water tables. This was followed by periods of warmer temperatures, higher water tables, coalescence of rain forest communities, and restriction of drier-habitat species to the bordering uplands they occupy at present. The pace of these changes produced a dynamism that was not experienced, at least to the same degree, by communities to the north. These differences in physiographic and climatic histories likely had an effect on the nature of speciation mechanisms operating in the three regions through a reordering of the components of the speciation process. Some residue of this reordering may still reside in large speciose genera distributed through northern Latin America in the form of morphological (leaf epidermal cell size, pollen aperture number, pollen sterility) and cytological (polyploidy) characters. If so, recognition of the separate histories may be useful in explaining features in modern taxa that are correlated with geography.


Download data is not yet available.


Metrics Loading ...




How to Cite

Graham, A. (1996). Paleophysiographic and paleoenvironmental histories in northern Latin America - Possible impact on modes of speciation. Journal of Palaeosciences, 45, 143–147.



Research Articles