干旱区生态环境知识资源中心

Aim To assess the correspondence between current avian distributions in the lowlands of northern South America with respect to the hypothesized importance of sea level rise and other events over the past 15 million years on speciation.

Location Tropical lowlands of north-western South America.

Methods To establish which bird taxa may have originated in each area of endemism, I examined the ranges of all bird species occurring in the Pacific and the Caribbean lowlands. To determine land and sea distribution during a sea level rise of 100 m in north-western South America and eastern Central America, I traced the 100 m contour line from the Geoatlas of Georama and the Global 30-Arc-Second Elevation Data (GTOPO30) produced by the US Geological Survey.

Results During a sea level rise of similar to100 m, marine incursions would have occurred from the Caribbean Sea and the Pacific Ocean. Several areas of tropical forest and dry/arid vegetation would have been isolated, currently known as the Darien, Choco, Nechi, Catatumbo, Tumbesian and Guajiran areas of animal and plant endemism.

Main conclusions A large part of the high diversity of forest and nonforest birds and other animals and plants in the Pacific rain forest and the Caribbean woodland likely arose as the result of sea level rises, dispersal and other geological and climatic events.