Genomic adaptations for tail-length evolution in arboreal snakes

Area of Science:

• Evolutionary Biology
• Genomics
• Developmental Biology

Background:

• Arboreal adaptation in snakes involves morphological innovations like elongated tails for improved branch gripping.
• The genetic basis for recurrent tail elongation in snakes adapting to arboreal environments is largely unknown.

Purpose of the Study:

• To investigate the genomic underpinnings of recurrent tail elongation in arboreal snakes.
• To identify genes and regulatory elements associated with axial elongation and tail development.

Main Methods:

• Ancestral state reconstruction to identify independent evolution of arboreality and tail elongation.
• Genome assembly of the green cat snake (Boiga cyanea) and comparative genomics with the Asian vine snake (Ahaetulla prasina).
• Analysis of gene evolution, including accelerated evolution and positive selection in somitogenesis genes, and examination of conserved nonexonic elements (CNEs).

Main Results:

• Arboreality and tail elongation evolved independently in multiple snake lineages.
• Accelerated evolution was found in genes related to somite specification, with positive selection in HES7 and TBX18.
• Conserved amino acid substitution in LOXL3 and convergent divergence in CNEs regulating the GDF11-LIN28-HOX13 pathway were observed in arboreal snakes.
• Functional assays confirmed altered regulatory activity of divergent CNEs.

Conclusions:

• Genomic changes in somitogenesis genes and regulatory elements contribute to snake axial elongation and tail length evolution.
• Convergent evolution at the genomic level underlies the recurrent adaptation of tail elongation in arboreal snakes.
• This study provides a genomic framework for understanding how arboreal specialization drives tail length evolution in snakes.