Comparative Genomics Provides Insights into Adaptive Evolution in Tactile-Foraging Birds

Tactile-foraging birds have evolved an enlarged principal sensory nucleus (PrV) but smaller brain regions related to the visual system, which reflects the difference in sensory dependence. The trade-off may exist between different senses in tactile foragers, as well as between corresponding sensory-processing areas in the brain. We explored the mechanism underlying the adaptive evolution of sensory systems in three tactile foragers (kiwi, mallard, and crested ibis). The results showed that olfaction-related genes in kiwi and mallard and hearing-related genes in crested ibis were expanded, indicating they may also have sensitive olfaction or hearing, respectively. However, some genes required for visual development were positively selected or had convergent amino acid substitutions in all three tactile branches, and it seems to show the possibility of visual degradation. In addition, we may provide a new visual-degradation candidate gene PDLIM1 who suffered dense convergent amino acid substitutions within the ZM domain. At last, two genes responsible for regulating the proliferation and differentiation of neuronal progenitor cells may play roles in determining the relative sizes of sensory areas in brain. This exploration offers insight into the relationship between specialized tactile-forging behavior and the evolution of sensory abilities and brain structures.

Automated summary

Tactile-foraging birds have adaptations in their sensory systems, with an enlarged principal sensory nucleus (PrV) and smaller brain regions related to the visual system. There may be a trade-off between different senses in these birds, as well as between corresponding sensory-processing areas in the brain. Olfaction-related genes are expanded in kiwi and mallard, indicating sensitivity to smell, while hearing-related genes are expanded in crested ibis, indicating sensitivity to hearing. However, genes related to visual development show signs of positive selection or convergent amino acid substitutions in all three tactile foragers, suggesting the possibility of visual degradation. Additionally, two genes responsible for regulating the proliferation and differentiation of neuronal progenitor cells may play a role in determining the relative sizes of sensory areas in the brain.