Coupling molecular evolution with macroevolutionary transitions in a pheromone system including the three amphibian...

Area of Science:

• Evolutionary biology
• Chemical ecology
• Amphibian biology

Background:

• Sodefrin precursor-like factors (SPFs) are key pheromones in amphibian reproduction, with origins traced to their last common ancestor.
• Previous research on SPF gene family evolution has largely excluded caecilians (Gymnophiona), leaving their diversity and evolutionary history incomplete.

Purpose of the Study:

• To investigate the molecular evolution of SPF pheromones in amphibians, incorporating data from caecilians.
• To understand the evolutionary history and gene duplication events within the SPF gene family across all three amphibian orders.

Main Methods:

• Inferred orthology relationships of amphibian SPFs from transcriptome data of 35 salamanders, five frogs, and eight caecilians.
• Performed phylogenetic comparative analyses to link pheromone delivery evolution, transmission environment, and SPF gene duplication events.

Main Results:

• Identified several orthologous groups within SPFs, suggesting multiple ancestral gene duplications.
• Discovered candidate caecilian SPFs clustering with Alpha and Beta SPFs, with Alpha SPFs previously found only in salamanders.
• Proposed that ancestral amphibians may have used terrestrial pheromone delivery, with aquatic courtship linked to SPF gene expansion in salamanders but not caecilians.

Conclusions:

• The inclusion of caecilians is vital for a comprehensive understanding of amphibian biology and pheromone system evolution.
• SPF gene evolution and associated reproductive behaviors differ between amphibian lineages, influenced by environmental factors and gene duplication events.