Dr. Werren's area of interest is evolutionary genetics. His research combines genetic, molecular, and population studies to investigate a variety of topics in evolution. Current research topics include: (1) evolution of inherited microorganisms, (2) genetic basis of morphological and behavioral differences between species, and (3) genetic conflict and the evolution of "parasitic" or "selfish" DNA.
Wolbachia are a widespread and common group of cytoplasmically inherited bacteria that cause reproductive incompatibility, parthenogenesis and feminization in their hosts. Studies are underway to investigate genome co-evolution of Wolbachia and their hosts, distribution and movement of Wolbachia in global and local insect communities, and mechanisms of action of Wolbachia. Key questions concern how these bacteria move between host species and whether they promote speciation in invertebrates. This work is part of a five-year multi-institutional NSF grant to investigate evolutionary and ecological genetics of Wolbachia. Dr Werren is the PI and coordinator of this grant.
Nasonia consist of a complex of three closely related species. Research efforts are geared towards investigating the genetic basis of morphological, behavioral, and developmental differences between the species. The ultimate goal is to identify the genes involved in species differences and speciation. The haplodiploid genetics of Nasonia make this complex of species particularly suited for genetic studies of speciation and species differences. We are currently using Nasonia to study the genetic basis of wing size differences. Male wing size differs by 2.5 fold between the species, with small vestigial wings having evolved in one species. The differences are due primarily to differences in cell size. Female wing sizes are similar in the three species. Therefore, this represents the neo-evolution of a sex specific and tissue specific regulation of cell size. Our genetic analysis reveals a few loci of major effect are responsible for the species difference. In Nasonia we can readily introgress genes from one species into the genetic background of another. This approach is being used for fine-scale genetic analysis and positional cloning of wing genes. The goal is to determine the genetic (e.g. sequence) and developmental changes associated with wing size, and the adaptive significance of this trait.
The three Nasonia species also differ in male courtship and female mate preferences. Using similar approaches to those above, we have introgressed loci affecting mate preferences between the species and are using these to investigate the genetic and behavioral underpinnings of mate choice and to test sexual selection theories.
Genetic conflict is an inherent feature of sex determining systems. For example, conflicting selective pressures occur between cytoplasmically and chromosomally inherited genes, and between maternal effect and zygotic sex determining loci. We are combining theoretical and empirical approaches to investigate the genetic basis of sex determination and the role of genetic conflict in sex determination evolution.
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