Evolution of Reproductive Isolation and Speciation in Neurospora

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The object of the research is to understand how barriers to hybridization evolve as populations diverge into separate species. This problem will be addressed by studying hybrid crosses between two geographically and genetically isolated populations of Neurospora crassa, a filamentous fungus (mold) that is one of the best studied organisms in biology, and between N. crassa and its close relative N. intermedia. This project has two main goals. The first is to identify and measure the individual components of reproductive isolation operating throughout the sexual pathway, from defects in mating interactions between hybridizing parents to inviability of hybrid offspring. The second goal is to map genetic loci controlling reproductive isolation barriers and to test hypotheses about the evolutionary genetics of reproductive isolation under different biogeographic scenarios. The evolution of reproductive isolation is a key event in the origin of new species, and it is hoped that this research will add to our scant understanding of a foundational mechanism that promotes biodiversity on Earth. In Neurospora, as in many species, the intensity of reproductive isolation is geographically structured: for a given species pair, hybridizing parents from disparate locations are more interfertile than hybridizing parents from the same location. This observation suggests that baseline reproductive isolation evolving between geographically isolated species is reinforced by natural selection against hybridization when species occur together. The work undertaken here aims to understand the genetic basis of this process.