An integrated DNA barcode and ecological trait dataset for the Tuscan Archipelago butterflies: a resource to understand the evolution and extinction of island biodiversity

Islands disproportionately contribute to biodiversity, but their restricted habitats amplify the impacts of stochastic events and human-induced effects. Although island biogeography postulates the importance of integrating molecular data with species traits in order to understand the evolution of endemic taxa, the persistence of relicts and the extinction of populations, very few such studies exist for species-rich animal groups over entire archipelagos. Results: We assembled a comprehensive DNA barcode dataset for the 52 butterfly species reported from the Tuscan Archipelago in the western Mediterranean, including comparative material from neighbouring areas (Sardinia, Corsica, and Tuscany). We also compiled data on 10 species traits and on the disappearance of some of the butterfly species from the main islands of this archipelago in the last 115 years. We assessed (i) the phylogeographic structure of each species across the study area, as well as (ii) the overall phylogeographic pattern in the same region, and (iii) identified the traits associated with population diversification, uniqueness, or recent extinction from specific islands. There was a considerable degree of population diversification in many species, which confirms that the Tuscan Archipelago hosts highly diverse butterfly communities. Phylogenetic regressions showed that smaller-sized and more specialized species, with a preference for drier regions, display greater genetic structure and (or) uniqueness. Moreover, species adapted to colder and wetter areas and with shorter flight periods are more likely to become extinct. Significance: For the butterfly fauna of the Tuscan Archipelago, we analyzed fine-scale diversity patterns, their probable origins and the vulnerability of taxa to current and future environmental changes. The methodology used here represents a practical tool for evidence-based conservation prioritization, while the dataset provided serves as a resource for further research on island ecology and biodiversity.