A Tale of Appendages: Investigating Limb and Tail Variation in Salamanders

Area of Science:

• Evolutionary Biology
• Comparative Anatomy
• Phylogenetics

Background:

• Tetrapod limb and tail evolution is crucial for locomotion and balance, traditionally viewed through a life-history lens.
• Existing perspectives may not fully account for the morphological diversity observed in salamanders.
• Understanding these variations requires integrating phylogenetic history with ecological factors.

Purpose of the Study:

• To compare appendage proportions (limbs and tails) across salamander families, ecological groups, and sexes.
• To investigate the roles of phylogeny, ecological adaptation, and convergence in shaping these traits.
• To provide a multi-disciplinary phylogenetic perspective on salamander appendage evolution.

Main Methods:

• Utilized a dataset encompassing 44% of known salamander species.
• Employed a phylogenetic framework to analyze appendage proportions.
• Compared limb and tail morphology across different taxonomic families, ecological niches (aquatic vs. terrestrial), and sexes.

Main Results:

• Plethodontidae family exhibited shorter limbs; aquatic species showed longer limbs.
• Basal salamander families possessed shorter tails, while terrestrial species had wider tails.
• Significant family-specific divergence in limb proportions was observed (e.g., Ambystomatidae vs. Salamandridae).

Conclusions:

• Salamander body form is influenced by a combination of evolutionary history (phylogeny) and ecological drivers.
• Ecological adaptation and convergent evolution contribute to the observed patterns in appendage morphology.
• Further research incorporating traits like caudal vertebral number and foot shape can enhance understanding of Caudata appendage evolution.