Günter P. Wagner

Population genetics

Wagner's early work was focused on mathematical population genetics. Together with the mathematician Reinhard Bürger at the University of Vienna, he contributed to the theory of mutation–selection balance and the evolution of dominance modifiers. Later Wagner shifted his focus on issues of the evolution of variational properties like canalization and modularity. He introduced the seminal distinction between variation and variability, the former describing the actually existing differences among individuals while the latter measures the tendency to vary, as measured in mutation rate and mutational variance. He published the first mathematical model for the evolution of genetic canalization,^[3] and thus contributed to the renaissance of studies of canalization in the mid 1990s. His more recent work is on the measurement of gene interaction, the evolution of evolvability and how it relates to the evolution of genetic architecture.^[4]

Evolutionary developmental biology

With the advent of comparative developmental genetics in the early 1991 Wagner's research program shifted towards the molecular evolution of developmental genes, initially Hox genes and Hox gene clusters. The Wagner lab was the first to identify major blocks of ultraconserved non-coding sequences in the intergenic regions between Hox genes,^[5] and dated the “fish-specific” Hox cluster duplication to nearly coincide with the most recent common ancestor of Teleostei fish.^[6] This work led to the theory that Hox cluster and genome duplications create a window of opportunity which, if coincidental with ecological changes, can lead to the fixation of these genes and novel gene functions.^[7]

In recent years the Wagner lab has focussed on the evolution of gene regulatory networks, in particular the role of transcription factor protein evolution in evolutionary innovation.^[8] In August 2016, an article by Wagner and Mihaela Pavlicev, gained attention for proposing a possible evolutionary connection between the female orgasm in humans and ovulation induced by copulation in other mammals.^[9]

Homology and innovation

A key conceptual and mechanistic problem in evolutionary biology is the nature of character identity, aka homology. Wagner was an early proponent of a mechanistic understanding of homology,^[10][11] together with Louise Roth at Duke University and Gerd Müller at the University of Vienna. A test case for this approach arose when Wagner and his colleague Jacques Gauthier proposed a solution of the century-old problem of the identity of avian digits.^[12] The core of the problem is that the three digits in the bird wing have the morphology of digits 1, 2, and 3, but develop from the digit condensations 2, 3, and 4, which according to some shows that they should be digits 2, 3, and 4. Wagner and Gauthier proposed that during the evolution of theropod dinosaurs, the closest relatives of birds, digits have "changed place" so that in the bird wing digit 1 develops from position 2 and digit 2 from position 3 and digit 3 from position 4 in the wing bud. This view is now strongly supported by molecular and experimental evidence and shows how mechanistic insights can solve seemingly intractable conceptual problems.

According to Wagner the homology concept has a complementary twin, that of innovation. While homology refers to the historical continuity of character identity, the term innovation refers to the origin of novel characters, i.e. the origin of novel homologues. Therefore, Wagner and Müller argue that the origin and maintenance of character identity is a central goal of evolutionary developmental biology.^[13]