Local adaptation fuels cryptic speciation in terrestrial annelids

Area of Science:

• Evolutionary Biology
• Genomics
• Soil Ecology

Background:

• Cryptic speciation, the process of evolutionary divergence without clear morphological distinction, is a key area in evolutionary biology.
• Next Generation Sequencing (NGS) offers powerful tools for identifying genome-wide local adaptation signatures.
• Soil-dwelling organisms, like earthworms, present unique challenges and opportunities for studying cryptic speciation.

Purpose of the Study:

• To investigate the genetic and evolutionary basis of cryptic speciation in the earthworm genus Carpetania.
• To identify genome-wide local adaptation signatures and explore cryptic morphological evolution.
• To understand the role of local adaptation and regulatory divergence in shaping genome evolution in soil fauna.

Main Methods:

• Genotyping-By-Sequencing (GBS) was employed to analyze genome-wide genetic variability across 17 earthworm populations.
• Geometric morphometrics of genital chaetae were utilized to assess cryptic morphological evolution.
• Genomic analyses identified genes under selection and Single Nucleotide Polymorphisms (SNPs) in Untranslated Regions (UTRs).

Main Results:

• Genomic analyses identified three distinct cryptic species within the Carpetania genus.
• Local adaptation was detected in over 800 genes, particularly those involved in reproduction, metabolism, immunological response, and morphogenesis.
• Shared mutations and enrichment of genes related to transcription regulation were observed in species under selection.

Conclusions:

• Local adaptation and regulatory divergence are identified as primary evolutionary forces driving genome evolution in soil fauna.
• Genomic and morphological data provide insights into the processes of cryptic speciation in earthworms.
• The study highlights the utility of integrative taxonomy and NGS in uncovering cryptic biodiversity.