In subdivided populations, adaptation to a local environment may be hampered by
maladaptive gene flow from other subpopulations. We study a continent-island model in
which an ancestral population sends migrants to a colony exposed to a different
environment. At an isolated locus, i.e., unlinked to other loci under selection, a locally
beneficial mutation can be established and maintained only if its selective advantage
exceeds the immigration rate of alternative allelic types. We show that, if a beneficial
mutation arises in linkage to a locus at which a locally adapted allele is already segregating
in migration-selection balance, the new mutant can invade and be maintained under much
higher immigration rates than predicted by one-locus theory. We deduce the maximum
amount of gene flow that admits the preservation of the locally adapted haplotype on the
strength of recombination and selection. We calculate the selective advantage of
recombination-reducing mechanisms, such as chromosome inversions, which often seem to
play a role in speciation. Our analysis provides conditions for the evolution of clusters of
locally adaptive genes, or islands of divergence, as found by some empirical studies. For an
extended model that allows for epistasis, we discuss how much gene flow is needed to
inhibit speciation by the accumulation of Dobzhansky–Muller incompatibilities.
Biography
I obtained my PhD in Mathematics from the University of Vienna in 1979. My dissertation
was in the field of harmonic analysis. In the early 1980s, I started working in mathematical
population genetics, which has been my main field of research since then. After some
postdocs, I got a position as a University assistant at the University of Vienna in 1982. I was
tenured in 1988, promoted to Associate Professor in 1996, and awarded the title University
Professor in 2008. In 1991, I was Visiting Researcher at the Division of Animal Production of
the CSIRO in Prospect, Australia, and in 1992/93, I was Visiting Full Professor at the
University of Oregon, Eugene, OR. Between 2004 and 2009, I spent about 11 months as
Visiting Scholar at Harvard University.
My research area is mathematical population genetics and evolutionary theory. Much of my
research has been devoted to the evolution of multilocus systems and quantitative traits
under the combined action of selection, recombination, and mutation. In recent years, my
work focused on the role of spatially heterogeneous selection in maintaining genetic
variation in geographically structured populations, and on the evolution of local adaptation
and differentiation.