Isolated populations within species gradually diverge genetically through the combined effects of mutation, genetic drift, and natural selection. Two types of selection may be important: (1) selection for adaptation to local environments (which has received wide attention), and (2) selection favoring coadapted sets of alleles within each population. The proposed work focuses on the latter process, which has been relatively understudied. Coadaptation is best observed in laboratory crosses between individuals from isolated populations. Such crosses typically result in reduced physiological performance in second-generation hybrids as the coadapted sets of alleles within each population are disrupted by recombination. Using the copepod Tigriopus californicus as a model system, the proposed experiments will assess the level of coadaptation in two physiological/genetic systems: (1) activity of the enzyme cytochrome c oxidase, and (2) rates of transcription of ribosomal RNA genes. Both these systems are known to require extensive gene interaction, making them especially likely to experience selection for coadaptation.
The proposed studies of coadaptation within populations are fundamental to understanding the importance of genetic variation within and between natural populations. Although the maintenance of genetic diversity is often espoused as a primary goal of conservation efforts, the extent to which such variation is vital to the ecology and evolution of species is poorly understood. By focusing on the function of genetic diversity in natural populations, the proposed work may provide a firmer experimental basis for such conservation efforts.
