The news finally came through this past week that my first Alaska INBRE Pilot grant was awarded. The goal of the proposed research is to develop a general evolutionary theory to understand host-symbiont interactions. This is an important missing component of current investigations of the human microbiome and its interpretation in regard to human health. In terms of human pathogens, we may better understand the conditions for disease emergence as well as those that favor increases and decreases in disease virulence.
Mike Wade and I recently published a population genetics analysis of indirect genetic effects. We found that the coadaptive process between genes and heritable environments is much faster thangenetic adaptation to an abiotic environment. Most interestingly, the effects of increased inbreeding accelerate the adaptive process than equivalent amounts of linkage. We are currently extending this model to other kinds of genome interactions. Below is the abstract, be sure to check out the full paper online at Evolution. and you can find the data online at Dryad.
Populations evolve in response to the external environment, whether abiotic (e.g., climate) or biotic (e.g., other conspecifics). We investigated how adaptation to biotic, heritable environments differs from adaptation to abiotic, non-heritable environments. We found that, for the same selection coefficients, the coadaptive process between genes and heritable environments is much faster than genetic adaptation to an abiotic non-heritable environment. The increased rate of adaptation results from of the positive association generated by reciprocal selection between the heritable environment and the genes responding to it. These associations result in a runaway process of adaptive coevolution, even when the genes creating the heritable environment and genes responding to the heritable environment are unlinked. Although tightening the degree of linkage accelerates the coadaptive process, the acceleration caused by a comparable amount of inbreeding is greater, because inbreeding has a cumulative effect on reducing functional recombination over generations. Our results suggest that that adaptation to local abiotic environmental variation may result in the rapid diversification of populations and subsequent reproductive isolation not directly but rather via its effects on heritable environments and the genes responding to them.