Patterns of transposable element variation and clinality in Drosophila

Area of Science:

• Evolutionary biology
• Population genetics

Background:

• Natural populations face spatially varying selection across diverse environments.
• Drosophila species (D. melanogaster and D. simulans) inhabit wide environmental ranges in North America, making them ideal models for studying adaptation.
• Transposable elements (TEs) are mobile genetic sequences whose variation can impact evolution.

Purpose of the Study:

• To investigate patterns of transposable element (TE) variation in natural populations of Drosophila melanogaster and Drosophila simulans across North American latitudes.
• To determine if spatial variation in the environment influences TE abundance and allele frequencies.
• To assess the role of local adaptation and demography in shaping TE diversity.

Main Methods:

• Sampling of D. melanogaster and D. simulans from multiple latitudes across North America.
• Characterization of transposable element (TE) variation and abundance.
• Analysis of TE allele frequencies and ancestry.
• Comparison of TE patterns with latitudinal gradients and environmental factors.

Main Results:

• A nearly twofold excess of TEs was observed in D. melanogaster compared to D. simulans, primarily driven by low and high-frequency TEs.
• No significant effect of latitude on total TE abundance or average TE allele frequencies was found in either species.
• Common patterns of TE variation did not correlate with the latitudinal gradient or environmental differences, and ancestry clines were absent for TEs and SNPs in D. melanogaster.

Conclusions:

• While widespread clinality of TEs was not evident in these North American Drosophila populations, TEs may still play a role in adaptation.
• Demographic factors appear to have a limited impact on shaping TE variation patterns.
• Further research is needed to develop models for adaptation to large-scale environmental heterogeneity, particularly concerning TEs.