Contrasting patterns of adaptive sequence convergence among echolocating mammals

Area of Science:

• Evolutionary biology
• Molecular evolution
• Comparative genomics

Background:

• Recent studies suggest adaptive sequence convergence in auditory genes between echolocating bats and dolphins.
• Previous findings for Otoferlin (Otof), Cadherin 23 (Cdh23), and Protocadherin 15 (Pcdh15) were based on limited phylogenetic evidence.

Purpose of the Study:

• To clarify whether echolocating bats and dolphins exhibit true adaptive sequence convergence in key auditory genes.
• To investigate the patterns of convergent and divergent amino acid substitutions across a deep mammalian phylogeny for Otof, Cdh23, and Pcdh15.

Main Methods:

• Phylogenetic analysis of 22-32 mammalian species for Otof, Cdh23, and Pcdh15.
• Estimation of convergent and divergent amino acid substitutions along independent evolutionary branches.
• Comparison of convergence patterns between bat suborders (Yangochiroptera, Yinpterochiroptera) and dolphins.

Main Results:

• No significant convergence was found for Pcdh15 between bats and dolphins.
• Minimal convergence for Otof was observed between Yinpterochiroptera and dolphins.
• High convergence for Cdh23 was detected between dolphins and Yinpterochiroptera, and unique convergence between dolphins and high-frequency Yangochiroptera bats.
• Contrasting convergence patterns suggest independent evolution of echolocation in the two bat suborders.

Conclusions:

• Convergent evolution of Cdh23 likely resulted from selection for high-frequency hearing.
• The distinct patterns of gene convergence support the hypothesis of independent origins of echolocation in Yangochiroptera and Yinpterochiroptera bats.
• This study provides molecular evidence for the independent evolution of complex traits like echolocation.