Caught in the Act: Human-Mediated Dispersal Induces a Viable Reptile Hybrid Population

Unintentional species translocations can trigger hybridization with profound evolutionary and conservation consequences. The very onset of such processes is rarely documented. The recent discovery of a novel Cryptoblepharus skink population on the remote island of Tromelin prompted investigation into its origins and genetic identity. Population genomic analyses reveal that this lineage arose from immediate hybridization between two vicariant species, C. bitaeniatus and C. caudatus. Both species were likely introduced in very small numbers during supply rotations of the logistics vessel Marion Dufresne in 2011 and 2019. Genomic evidence indicates the establishment of a viable, self-sustaining hybrid population characterized by near-equal ancestry proportions, strong founder effects, and genetic divergence from both parental taxa. The emergence of this independent hybrid lineage in an isolated environment offers proof-of-principle for human-mediated insular hybridization, distinct from the common scenario of an invading genome introgressing into a resident species. These findings underscore that inadequate biosecurity measures not only threaten native biodiversity but may also inadvertently unlock novel evolutionary trajectories.