Gene regulatory divergence among species estimated by altered developmental patterns in interspecific hybrids

Disturbances in the schedules of gene expression in developinginterspecific fish hybrids have been used to draw inferences about theextent of gene regulatory divergence between species and about the degreeto which this gene regulatory divergence is correlated with structural genedivergence, as estimated by genetic distance. Sperm from each of 10different species representing six genera within the family Centrarchidaewas used to fertilize eggs of the Florida largemouth bass (Micropterussalmoides floridanus). The genetic distances (D; Nei 1978) between theparental species used to form the hybrids ranged from 0.133 to 0.974. Thedevelopmental success and temporal patterns of gene expression of each ofthe hybrids were compared with those of the Florida largemouth bass. As thegenetic distance between the paternal species and the Florida largemouthbass increased, there was a general decline in developmental success in thehybrid embryos as demonstrated by the observed reductions in the percentageof hatching and by progressively earlier and more extensive morphologicalabnormalities. Concomitantly, progressively more marked alterations indevelopmental schedules of expression of 15 enzyme loci occurred in thehybrids as the genetic distance between parental species increased.However, observed deviations from this trend for a few species mayrepresent an uncoupling of the rates and modes of evolution of structuralgenes from those for genes regulating developmental processes.