Transcriptome-wide patterns of divergence during allopatric evolution

Area of Science:

• Evolutionary Biology
• Genomics
• Marine Biology

Background:

• Species formation involves genomic divergence, with patterns suggesting natural selection targets specific genes.
• Closely related species often share evolutionary constraints limiting genetic variability.
• Studying divergence within a species, like Tigriopus californicus, offers insights into evolutionary processes.

Purpose of the Study:

• To investigate transcriptome-wide divergence and polymorphism in Tigriopus californicus.
• To understand the roles of adaptive and nonadaptive processes in repeatable genomic divergence.
• To identify specific genes and proteins involved in allopatric divergence.

Main Methods:

• Analysis of transcriptome-wide divergence and polymorphism in Tigriopus californicus populations.
• Comparative analysis across five interpopulation comparisons at three divergence stages.
• Examination of nonsynonymous mutation accumulation and signatures of positive selection.

Main Results:

• Small effective population sizes led to rapid loss of shared polymorphisms and fixation of slightly deleterious mutations.
• Nonsynonymous mutations consistently accumulated in specific proteins, including those in mitochondrial DNA (mtDNA) and those under positive selection.
• Both nonadaptive processes (genetic drift, gene expression) and adaptive evolution contribute to repeatable genomic divergence patterns.

Conclusions:

• Repeatable patterns of genomic divergence are driven by a combination of adaptive evolution and nonadaptive processes.
• Specific sets of genes are repeatedly targeted by natural selection during allopatric divergence.
• Evolutionary predictability at the gene level is influenced by both selection and constraints.