Study of the phylogenetic relationships between freshwater planarians from Chile, unknown species found in extreme and little-explored areas
Background. Planarians are bilateral triploblastic invertebrates from the phylum Platyhelminthes, with characteristics that make them valuable for research in regeneration biology, ecology of invasive species, ecotoxicology and systematics. Despite Chile's rich biodiversity and diverse ecosystems, including extreme environments like the Atacama Desert, Patagonia, and the Andes, the triclad fauna has been poorly studied, with only five freshwater Dugesiidae species reported. This study initiates a systematic exploration of planarians in unexplored areas, including the Chilean Altiplano, with the aim of beginning to elucidate the status of dugesid biodiversity in Chile.   Results. Based on morphological traits, such as head and auricle shapes, coupled with molecular studies of cytochrome oxidase I and elongation factor 1-a nucleotide sequences, we confirm that all species found in our survey belong to the genus Girardia. Phylogenetic analyses reveal three clades with independent evolutionary histories linked to their geographical distribution. Finally, using three single-locus species delimitation methods, we propose six new species present in Chile's territory. Conclusion. We reveal a broad presence of planarians in Chile with a higher diversity than previously reported, and we propose a number of new species. Our results indicate that planarians in Chile are widely distributed, inhabiting even extreme habitats, and suggest that more exhaustive studies may reveal even more diversity in this group.