Speciation typically occurs when two populations split and begin to accumulate genetic differences, which can lead to the evolution of reproductive isolating mechanisms (RIM) that prevent them from interbreeding in the future. Gene flow between species opposes this divergence, since it is a homogenizing force that can swamp genetic and phenotypic differences. Reproductive isolation as a barrier to gene flow must therefore be a key feature in the persistence of species. Species of the Drosophila genus remain some of the best models for the study of speciation. Nonetheless, studies of gene flow during the build up of reproductive isolation in Drosophila have been limited by the fact that very few hybrid zones are known in Drosophila. Our research uses a multi-level approach to discover the genetic mechanisms (within individuals and populations) and evolutionary consequences (for species pairs and for the entire Drosophila genus) of traits involved in reproductive isolation.
The importance of genetic exchange between species (i.e. introgression of genes from one species into another through hybrid intermediates) is a constant subject of debate among evolutionary biologists. While some claim genetic exchange is pervasive, others claim that it is extremely rare. Currently, there is little data quantitatively supporting either of these scenarios. We study naturally occurring hybrid zones and quantify the prevalence of genetic exchange between species to understand the frequency and evolutionary consequences of gene exchange. Fruit flies from the genus Drosophila can be collected in their natural habitat and also maintained under laboratory conditions, and have an unmatched arsenal of molecular genetic and genomic tools. This line of research involves natural collections, development of methods to detect introgression and functional characterization of putatively introgressed alleles. Our results provide a broad view of patterns of introgression in cases where species interbreed in nature.
Examples of lab publications:
Cooper, B.S., Ginsberg, P.S., Turelli, M. and Matute, D.R. 2017. Wolbachia in the Drosophila yakuba complex: pervasive frequency variation and weak cytoplasmic incompatibility, but no apparent effect on reproductive isolation. Genetics, 205: 333-351
Hybrid inviability One way to study the evolution of reproductive isolation is to identify alleles involved in inviability of hybrids. However, hybrid inviability signals more than just the evolution of reproductive isolation: it signals functional divergence in developmental pathways beyond what could be predicted from sequence divergence because it screens for genetic function. Our goal is to understand how function changes as divergence unfolds. We focus on species pairs that are highly diverged (10-15 mya) but still can interbreed and produce viable offspring. Our lab studies multiple hybrid crosses to not only dissect what genes cause inviability but also to reveal precisely how they do it and what are the evolutionary processes that have led to their divergence.
Examples of lab publications:
Miller, C.J. and Matute, D.R. 2017. The effect of temperature on Drosophila hybrid fitness. G3: Genes, Genomes,Genetics 7: 377-385
Matute D.R., Gavin-Smyth J. and Liu, G. 2014. Variable postzygotic isolation in Drosophila melanogaster/D. simulans hybrids. J. Evol. Biol 27: 1691–1705.
Matute D.R. and Gavin-Smyth J. 2014. Fine mapping of dominant X-linked incompatibility alleles in Drosophila hybrids. PLoS Genetics 10: e1004270.
Hybrid speciation, the evolutionary process in which hybrids become reproductively isolated from their parental species is argued to be common in plants but the importance of the process is hotly debated in animals and other clades. The difficulty of obtaining conclusive evidence for animal hybrid speciation has led to two camps in speciation research: those who state that hybrid speciation in animals is extremely rare, and those who consider the process to be rampant (if unproven) across all taxa. The correct answer is bound to lie somewhere in between these two extremes. Our research goal is to use carefully design experiments to understand the importance of controversial mechanisms of speciation. Experimental evolution provides the tools to understand the importance of hybrid speciation because if reproductive isolation evolves in an experimental hybrid lineage, no other explanation but hybrid speciation can be invoked. Drosophila is one of the few animal systems in which this experiment can be done because of its short generation time, sexual mode of reproduction, and availability of multiple hybridizing species pairs. Examples of lab publications:
Comeault A. A. and Matute D. R. An experimental test of hybrid speciation in Drosophila
Comeault, A.A. The genomic and ecological context of hybridization affects the likelihood of hybrid speciation driven by genetic incompatibilities.