Genomics Reveals Widespread Ecological Speciation in Flightless Insects

Area of Science:

• Evolutionary Biology
• Genomics
• Speciation Research

Background:

• Ecological gradients, particularly altitude, are increasingly recognized as drivers of parallel evolutionary divergence.
• Wing reduction and flight loss are hypothesized to be key factors in insect diversification, but their role in repeated speciation requires further investigation.
• Montane insect assemblages provide model systems to study the impact of environmental factors on evolutionary trajectories.

Purpose of the Study:

• To investigate the extent to which altitude-driven ecological gradients can lead to repeated speciation events.
• To test the hypothesis that wing reduction is a significant factor in the diversification of hexapods.
• To analyze the genomic basis of parallel speciation in a widespread, wing-polymorphic stonefly species complex.

Main Methods:

• Genomic analyses were performed on nearly 200 specimens of Zelandoperla fenestrata stoneflies.
• Over 50,000 polymorphic genetic markers were identified using a newly generated plecopteran reference genome.
• Genotyping-by-sequencing (GBS) was employed to generate high-resolution genetic data.

Main Results:

• Widespread parallel speciation was revealed between sympatric full-winged and wing-reduced ecotypes of Zelandoperla fenestrata.
• Evolutionary genomic data indicate that wing-reduced upland lineages have speciated repeatedly and independently, refuting the existence of a single widespread flightless taxon.
• A cluster of outlier single-nucleotide polymorphisms (SNPs) in a genomic region containing the doublesex gene suggests a role for this 'island of differentiation' in rapid ecological speciation.

Conclusions:

• Ecological speciation, driven by wing reduction in response to altitude, has occurred repeatedly and recently in Zelandoperla stoneflies.
• Independent evolution of reproductive isolation between ecotypes lacking mitochondrial DNA differentiation supports recent ecological speciation.
• The doublesex 'supergene' region may be a key genetic factor facilitating rapid adaptation and speciation in response to environmental pressures.