Diversity and divergence of two sympatric, sibling octopus species.

Whole-genome analysis reveals that Octopus bimaculatus has experienced stronger positive selection than O. bimaculoides over the past million years, with more adaptive mutations fixed.

• Why it matters: Understanding recent evolutionary processes in cephalopods is limited, especially regarding how population size influences natural selection and trait development in sympatric species.
• What they did: Researchers conducted a comparative population genomic study using whole-genome resequencing of the two octopus species, estimating divergence time and analyzing signatures of positive selection and mutation rates.
• The result: Findings suggest that larger effective population size in O. bimaculatus correlates with more efficient natural selection, particularly on genes related to brain and eye development, and indicate a female-biased mutation rate on the Z chromosome.