Significant variation for fitness impacts of ETS loci in hybrids between populations of Tigriopus californicus

The connections between the genes that cause hybrid incompatibilities and the physiological processes disrupted in hybrids by these incompatibilities are not well understood. The interactions between proteins in the electron transport system (ETS) in the copepod, Tigriopus californicus, have emerged as a potential model system to explore such connections. In this study, the effects on hybrid fitness of 3 different nuclear loci encoding proteins of the ETS are examined in hybrid copepods obtained from crosses of genetically divergent populations of this species. The potential interactions between these genes and mitochondrial-encoded proteins of the ETS are also explored; these interactions have been shown to have diverged functionally between these populations in other studies. Large deviations from Mendelian inheritance are found in genotypic ratios at each of the 3 loci in adults but not in nauplii, demonstrating genotype-based selection during development. The length of developmental time of hybrids appears to influence the pattern of deviations in these loci, likely in conjunction with levels of competition in these crosses. The major finding of this study is that in repeated crosses, the nature of deviations at these ETS loci shows dramatic differences suggesting that slight perturbations in initial conditions can dramatically shift the patterns of selection at these ETS loci in interpopulation hybrids.