Study of the phylogenetic relationships between freshwater planarians from Chile, unknown species found in extreme and little-explored areas
Background. Planarians have 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 represents the findings from a set of contrasting and environmentally interesting unexplored areas, including the Chilean Altiplano, that show several distinctive genetic clusters, an indicative of a much larger dugesid diversity waiting to be discovered.   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 several new species. Our results indicate that planarians in Chile are widely distributed, even inhabiting extreme habitats, and suggest that more exhaustive studies may reveal even more diversity within this group.