Polygenic evolution drives species divergence and climate adaptation in corals

Area of Science:

• Marine biology
• Genomics
• Evolutionary biology

Background:

• Closely related species exhibit ecological trait differences, but the genomic basis for adaptation is often unclear.
• Understanding the genetic underpinnings of species divergence is crucial for predicting responses to environmental change.

Purpose of the Study:

• To investigate the genomic basis of ecological divergence between two cryptic species of Acropora hyacinthus coral.
• To determine whether adaptation is driven by a few major genes or numerous genome-wide variations.

Main Methods:

• RNA-Sequencing (RNA-Seq) was used to compare gene expression patterns and genetic polymorphism between two Acropora hyacinthus species.
• Analysis focused on allele frequencies, gene expression differences, and types of genetic variants (polymorphisms).

Main Results:

• The two coral species share most polymorphisms but exhibit significant differences in allele frequencies and gene expression.
• Widespread gene expression changes correlate with regulatory variants, though genetic drift may play a role.
• Greater genetic divergence was observed in amino acid replacement polymorphisms than synonymous variants.

Conclusions:

• Polygenic evolution, involving numerous genetic loci, is a major driver of ecological divergence in Acropora corals.
• These genetic differences contribute to distinct environmental traits and resilience to climate change, such as thermal stress tolerance.