Population genetics in the American Tropics

Abstract

There are several Colombian populations of Drosophila pseudoobscura which have begun to show divergence. The temporal samples of Torobarroso, one of the local populations identified, demonstrate genetic "resourcefulness" and selective opportunism by fluctuating mortality. The data suggest that both balanced selection and mutational origin are necessary to account for the frequencies of drastic genes encountered. In genetic isolates there seems to exist alternatively a mutational component and a balanced - selection component. These components overcome the damage in the first instance and in the second instance, profit from the recessive load.

Mitochondrial gene divergence of Colombian Drosophila pseudoobscura

“…The smaller the founding population, the more drastic would be the loss of alleles in the first generation (Nei, Maruyama, and Chakrabority 1975). If population growth rate remained small because D. pseudoobscuru in Colombia was divided into several small demic populations, as Hoenigsberg et al (1983) suggest, then nucleotide diversity might have remained at low levels. Hoenigsberg et al (1988) proposed that the population structure of D. pseudoobscuru in Colombia is not panmictic.…”

“…The Colombian populations are separated from the nearest populations that are known in Mexico and Guatemala by 2,400 km. While North American and Guatemalan populations occupy a wide variety of habitats, the isolated Colombian populations inhabit an area of about 40,000 km2 of similar ecology across the high Andean plateau of Cundinamarca, Boyaca, and Santander, known as the cundiboyacense Altiplano (Hoenigsberg et al 1983(Hoenigsberg et al , 1988Cardenas and Hoenigsberg 1989). Other attempts to find the species in Costa Rica, in Panama, or on the other two high Andean plateaus in Colombia have been unsuccessful (Prakash 1972;Hoenigsberg et al 1983).…”

“…They calculated the net nucleotide divergence between the two populations and calibrated this divergence against a rate of 1.7% nucleotide substitutions per Myr (Caccone, DeSalle, and Powell 1988). Their estimated time of divergence between the Californian populations and the Colombian populations was 155,000 years, a result that supports neither a recent introduction (Prakash 1972) nor an ancient divergence (Ayala and Dobzhansky 1974;Dobzhansky 1974;Hoenigsberg et al 1983;Hoenigsberg 1986).…”