Population genetic diversity and fitness in multiple environments.

Background: When a large number of alleles are lost from a population, increases in individual homozygosity may reduce individual fitness through inbreeding depression. Modest losses of allelic diversity may also negatively impact long-term population viability by reducing the capacity of populations to adapt to altered environments. However, it is not clear how much genetic diversity within populations may be lost before populations are put at significant risk.

Genetic isolation and morphological divergence mediated by high-energy rapids in two cichlid genera from the lower Congo rapids.

Background: It is hypothesized that one of the mechanisms promoting diversification in cichlid fishes in the African Great Lakes has been the well-documented pattern of philopatry along shoreline habitats leading to high levels of genetic isolation among populations. However lake habitats are not the only centers of cichlid biodiversity - certain African rivers also contain large numbers of narrowly endemic species. Patterns of isolation and divergence in these systems have tended to be overlooked and are not well understood.

Size-dependent use of territorial space by a rock-dwelling cichlid fish.

Territoriality fundamentally influences animal mating systems and patterns of population structure. Although territory ownership is already known to contribute importantly to male reproductive success and the ecological coexistence of African rock-dwelling cichlids, the significance of variation in territory features has received little attention in these fishes. In Lake Malawi, males of Pseudotropheus tropheops "orange chest" defend territories on either of two substrate classes at Harbour Island: flat rock slabs lacking crevices and caves, or structurally complex boulder fields containing cave shelters.

Convergent evolution of Darwin's finches caused by introgressive hybridization and selection.

Between 1973 and 2003 mean morphological features of the cactus finch, Geospiza scandens, and the medium ground finch, G. fortis, populations on the Galápagos island of Daphne Major were subject to fluctuating directional selection. An increase in bluntness or robustness in the beak of G.

Using nuclear haplotypes with microsatellites to study gene flow between recently separated Cichlid species.

When populations or species have recently separated they often share genetic variation. However, it can be difficult to determine whether shared polymorphisms are the result of gene flow, the result of the persistence of variation in both populations since the time of common ancestry, or both of these factors. We have developed an empirical protocol for using loci that include unique nuclear DNA sequence haplotypes together with linked microsatellites or short tandem repeats (STRs).

Inbreeding and interbreeding in Darwin's finches.

Studies of inbreeding and interspecific hybridization are generally pursued separately with different metrics. There is a need to integrate them because they have the common goal of seeking an understanding of the genetic and ecological basis of fitness variation in populations. We use mean expected heterozygosity as an axis of variation on which to compare the fitness of inbreeding and hybridizing Darwin's finches (Geospiza scandens and G.

Inferring the history of speciation from multilocus DNA sequence data: the case of Drosophila pseudoobscura and close relatives.

The divergence of Drosophila pseudoobscura from its close relatives, D. persimilis and D. pseudoobscura bogotana, was examined using the pattern of DNA sequence variation in a common set of 50 inbred lines at 11 loci from diverse locations in the genome.