Diversification linked to larval host plant in the butterfly Eumedonia eumedon

Area of Science:

• Ecology and Evolutionary Biology
• Genetics
• Entomology

Background:

• Insect diversification is influenced by host plant associations.
• Host-associated genetic differentiation (HAD) and reproductive isolation mechanisms in insects are understudied.
• Lepidoptera diversity offers a model for investigating HAD.

Purpose of the Study:

• To investigate HAD processes in the Geranium argus butterfly (Eumedonia eumedon).
• To analyze the genetic structure and reproductive isolation of E. eumedon populations.
• To test for isolation by ecology (IBE) versus isolation by distance (IBD) in this species.

Main Methods:

• Genomic data analysis to reveal genetic structure.
• Investigating host plant relatedness and its correlation with genetic differentiation.
• Comparing IBE and IBD patterns at local and European scales.

Main Results:

• Identification of multiple host races of E. eumedon, some within the Cantabrian Mountains.
• Significant pattern of IBE mediated by HAD at both local and European scales.
• Genetic differentiation correlated with host plant taxonomic relatedness; IBD significant only at the European scale.

Conclusions:

• Host plant relatedness is a key driver of genetic differentiation and reproductive isolation in E. eumedon.
• Allochrony (shifted flight times) may contribute to local HAD between Geranium-feeding populations.
• Other mechanisms beyond allochrony and IBD are likely responsible for reproductive isolation between Erodium- and Geranium-feeding populations.