Deforestation-induced Hybridization in Philippine Frogs Creates a Distinct Phenotype With an Inviable Genotype

Area of Science:

• Evolutionary Biology
• Genomics
• Herpetology

Background:

• Hybridization significantly impacts evolutionary trajectories and can obscure species boundaries.
• The taxonomy and evolutionary history of Philippine narrow-mouthed frogs (Kaloula) are poorly understood, particularly within the Kaloula conjuncta complex.
• Kaloula conjuncta stickeli, a rare subspecies, has unique characteristics but unclear evolutionary relationships.

Purpose of the Study:

• To empirically demonstrate how hybridization confounds phylogenetic inference, species boundaries, and taxonomy.
• To investigate the evolutionary history and taxonomic status of the Kaloula conjuncta complex.
• To assess the taxonomic validity of Kaloula conjuncta stickeli.

Main Methods:

• Target-capture sequencing was employed to analyze genetic data.
• A robust analytical framework integrating morphological, phylogenomic, clustering, and distance-based methods was used.
• Network multispecies coalescent and population genetic approaches were utilized to infer reticulate evolutionary history.

Main Results:

• Kaloula conjuncta stickeli shares alleles with Kaloula conjuncta meridionalis and Kaloula picta.
• Despite a distinct phenotype, K. c. stickeli is identified as an inviable F1 hybrid between K. c. meridionalis and K. picta.
• Standard systematic inference methods produced misleading results for hybrid identification, while coalescent and population genetic methods accurately inferred reticulate evolution.

Conclusions:

• Kaloula conjuncta stickeli does not warrant taxonomic recognition as it is a hybrid.
• Hybridization can create artefactual branch effects, misleading phylogenetic analyses and taxonomic assessments.
• Deforestation-induced hybridization is a potential phenomenon with significant conservation implications in Southeast Asia.