Genomic Signatures of Speciation in Butterflies

Area of Science:

• * Evolutionary Biology
• * Genetics
• * Zoology

Background:

• * Species delineation is fundamental to biology but lacks simple, quantitative standards.
• * Ambiguous species boundaries pose challenges in conservation, agriculture, law, and education.
• * Butterflies serve as a model system to investigate species classification challenges.

Purpose of the Study:

• * To establish quantitative criteria for species delimitation using butterfly genetic data.
• * To investigate the role of the Z chromosome in the speciation process.
• * To identify genetic and molecular factors associated with speciation.

Main Methods:

• * Transcriptome sequencing and analysis of 186 butterfly specimens from 25 species pairs.
• * Calculation of fixation index and gene flow on Z-linked genes to assess reproductive isolation.
• * Analysis of protein divergence and positive selection in genes related to key biological functions.

Main Results:

• * A combination of fixation index and gene flow on Z-linked genes robustly separates species from conspecific populations.
• * Nine debated butterfly pairs were identified as distinct species based on these criteria.
• * Elevated divergence and positive selection in specific protein-coding genes correlate with speciation, with a notable role for Z-chromosome genes.

Conclusions:

• * Quantitative genetic criteria can effectively delimit species, resolving taxonomic debates.
• * The Z chromosome plays a significant role in butterfly speciation and shows reduced introgression.
• * Common speciation mechanisms may exist in butterflies, aiding biodiversity exploration and conservation.