Understanding the Genetics of Speciation

Not in peppered moths but in the geneticists long term workhorse Drosophila. The genes Nup160 and Nup96 which produce proteins involved in the nuclear pore complex have both been shown to cause hybrid incomaptibilites between D. simulans and D. melanogaster (Presgraves et al., 2003;Tang and Presgraves, 2009). This is an example I happen to recall, I'm sure there are others. It is wrong to assume the incompatibilities need to be based on something as major as differences in chromosome number. As my above example shows, small alterations in one or 2 genes may be sufficient. There is a term 'Dobzhansky-Muller genes' which describes pairs of genes fulfilling a set of criteria ... One paper discussing such genes (Brideau et al., 2006) is interesting as it again describes hybrid incompatibility between D. simulans and D. melanogaster. In fact the experiments done in the Nup160/Nup96 papers were performed on hybrids which had had the incompatibility caused by the appropriately named Lethal hybrid rescue gene rescued, protecting the hybrid males from their usual fate of death.This highlights the fact that not one but several different genetic differences have accrued between D. Simulans and D. melanogaster which have caused hybrid incompatibilities.The point about Dobzhansky-Muller genes is that the mutation of one such gene within a population after it has diverged from its sister population will not produce incompatibility, it is in the interaction with genes in the sister population which have themselves diverged from their common ancestor that the incompatibility arises.TTFN,WKEdited by Wounded King, : No reason given.

I haven't read these papers but a quick literature search turned up a few candidates. In this paper the authors describe a series of crosses for 9 lines of Acantocyclops which had well characterised gentics and morphology and measured their comparative reproductive isolation on these bases (Grishanin et al., 2006). This set of species/subspecies showed multiple viable crosses betweeen partners with different chromosome numbers. In this paper the authors describe viable hybrids from 2 subspecies of ant with differing chromosome numbers (Buschinger and Fischer, 1990). Hmm, having just looked back I don't see them actually crossing the hybrids, so maybe this paper doesn't show it at all, oops.I'll keep looking.TTFN,WK

It is wildly misleading to put up the camel and llama as an example where 'Genetic incompatibility doesn't need to occur to develop different organisms adapted to different ecologies'. It is incredibly difficult to produce viable llama/camel hybrids there is a very high rate of spontaneous abortions and no evidence that these hybrids are fertile, these are not the hallmarks of a lack of genetic incompatibility. Indeed in their paper describing one of the successful crosses Skidmore et al. (1999) note ... Your point is good but your example fails to be an example of it.TTFN,WK