Wolbachia-driven selective sweep in a range expanding insect species

Area of Science:

• Evolutionary biology
• Genetics
• Symbiosis

Background:

• Spatial genetic signatures can reveal obscured evolutionary processes.
• The maternally inherited bacterium Wolbachia is a widespread insect symbiont.
• Wolbachia manipulates host reproduction, potentially causing mitochondrial haplotype hitchhiking.

Purpose of the Study:

• To investigate Wolbachia prevalence and its impact on the genetic diversity of the common bluetail damselfly (Ischnura elegans).
• To explore Wolbachia's biogeographic variation across Europe and Japan, and in related Mediterranean species.
• To understand how symbiont infections shape host evolutionary genetics during range expansion.

Main Methods:

• Screening for Wolbachia infection across 17 populations of Ischnura elegans in Europe and Japan.
• Analyzing genetic variation in mitochondrial DNA.
• Comparing infection rates and genetic diversity in relation to latitude and geographic origin.

Main Results:

• Multiple Wolbachia strains were identified, with evidence of transfer through hybridization.
• Higher Wolbachia infection rates were observed at higher latitudes.
• North-western European populations of I. elegans showed reduced mitochondrial diversity, consistent with Wolbachia hitchhiking.

Conclusions:

• Endosymbiont infections like Wolbachia can significantly shape spatial variation in host evolutionary genetics.
• Postglacial expansion dynamics are influenced by symbiont prevalence.
• Population genetic studies must account for symbiont infections to accurately interpret mitochondrial genetic diversity patterns.