H. Allen Orr

H. Allen Orr
Fields	Evolutionary biology, Genetics
Institutions	University of Rochester
Notable awards	2008 Darwin-Wallace Medal

H. Allen Orr is University Professor and Shirley Cox Kearns Professor of Biology at the University of Rochester.

Orr earned his bachelor's degree in Biology and Philosophy from the College of William and Mary and his Ph.D. in Biology from the University of Chicago. At Chicago, Orr studied under Jerry Coyne. He performed postdoctoral research at the University of California, Davis.

Orr is an evolutionary geneticist whose research focuses on the genetics of speciation and the genetics of adaptation, in particular on the genetic basis of hybrid sterility and inviability. How many genes cause reproductive isolation between species? What are the normal functions of these genes and what evolutionary forces drove their divergence? He studies these problems through genetic analysis of reproductive isolation between species of Drosophila.

In his adaptation work, Orr is interested in theoretical rules or patterns that might characterize the population genetics of adaptation. He studies these patterns using both population genetic theory and experiment. His early work on Drosophila set the terms of much of the current research on speciation. Orr is said to be one of the few evolutionary biologists ever to have made fundamental contributions about how changes occur within lineages over time, and about how lineages split to result in new species.

His book Speciation, co-authored with Jerry Coyne, was hailed in Science as "exceedingly well-written and persuasive". They consider that studying speciation is largely synonymous with studying reproductive isolation, and explore what we know about where, when, and how isolating barriers evolve. Following Ernst Mayr they argue that speciation usually occurs where populations are geographically isolated or allopatric. They present evidence for the primacy of natural and sexual selection over genetic drift in driving speciation. Signatures of positive selection on genes involved in postzygotic isolation and reproductive proteins as well as experimental evidence from both the lab and field connect adaptation and sexual selection to reproductive isolation. They also present evidence for the congruence of the Dobzhansky-Muller model for the evolution of postzygotic isolation with the genetics of hybrid incompatibilities in many natural systems. Results that support their conclusions in the book continue to be published

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