Date:
Location:
Catherine Linnen
Associate Professor
University of Kentucky
From genes to species: How ecological divergence causes reproductive isolation
Abstract: Plant-feeding insects are unusually diverse, but the mechanisms that give rise to this pattern remain unclear. To understand these mechanisms, my lab uses pine sawflies in the genus Neodiprion as a model. First, I will summarize comparative and population genomic work documenting a pervasive pattern of host-associated divergence: within populations, among populations, between closely related species, and among 19 eastern North American sawflies adapted to different pines. Then, to characterize the mechanisms that produce this pattern, I will focus on a pair of hybridizing sister species adapted to different pines. Demographic modelling suggests that sister species Neodiprion lecontei (redheaded pine sawfly) and N. pinetum (white pine sawfly) most likely diverged with continuous gene flow. One explanation for how these species have remained morphologically, behaviorally, and genetically distinct in the face of gene flow is that the genes underlying host-use are tightly clustered in the genome, reducing recombination. To test this hypothesis, we used a QTL mapping approach to characterize the genetic architecture of several host-use traits. Contrary to our predictions, we found that host-use loci occur in many different regions of the genome. We also found evidence of host-associated fitness trade-offs for several egg-laying traits. In combination, these traits render hybrid females ecologically sterile. Taken together, our data suggest that causal genes underlying QTL peaks can be considered “speciation genes” and that reduced recombination is not necessary for sympatric speciation via host shift. Together, these data shed light on herbivorous insect diversity.
Host: OEB Graduate Students
Live stream: https://bit.ly/41RwyAz