Lineage-specific histories rather than shared drivers shape olfactory evolution in New World monkeys

Convergent reductions in olfactory receptor repertoire size across New World monkeys arise via distinct genomic routes, while olfactory bulb size covaries only partially within lineages.

• Why it matters: Prior links between repertoire variation and ecological or sensory drivers are lineage-specific, leaving uncertainty about whether shared drivers or lineage histories dominate olfactory evolution.
• What they did: Using genomic data from 80 New World monkey species plus CT-based olfactory anatomy and ecological measures, the study tested how ecological and sensory variables explain repertoire variation and how repertoire size relates to olfactory bulb volume.
• The result: Ecological and sensory variables explain little variation; titi monkeys show extensive gene inactivation, squirrel monkeys show large structural deletions, owl monkeys retain a large ancestral repertoire and enlarge olfactory bulb, and repertoire–bulb covariation is only partial within lineages.

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