One, two or three? Integrative species delimitation of short-range endemic Hemicycla species (Gastropoda: Helicidae) from the Canary Islands based on morphology, barcoding, AFLP and ddRADseq data

Hemicycla mascaensis and H. diegoi are short-range endemics that occur allopatrically in small areas in the Teno Mountainis in the western part of Tenerife (Canary Islands). Both taxa have been recognised as distinct species based on differences in shell morphology and genital anatomy. Preliminary molecular analyses using mitochondrial markers suggested a potential paraphyly of H. diegoi with regard to H. mascaensis. We here use multilocus AFLP data and ddRADseq data as well as distribution data and previously published data on shell morphology and genital anatomy to assess the status of the two taxa using phylogenetic analyses, species tree reconstruction and molecular species delimitation based on the multispecies coalescent as implemented in BFD* and BPP in an integrative approach. Our analyses show that, based on the analysis of multilocus data, the two taxa are reciprocally monophyletic. Species delimitation methods however tend to recognise all investigated populations as distinct species, albeit neither lending unambiguous support to any of the species hypothesis. This highlights the need for a balanced weighting of arguments from different lines of evidence to determine species status and calls for cautious interpretation of the results of molecular species delimitation analyses, especially in organisms with low active dispersal capacities and expected distinct population structuring such as land snails. Taking all available evidence into account, we favour to recognise H. mascaensis and H. diegoi as distinct species, acknowledging however that the recognition of both taxa as subspecies would also be an option as morphological differentiation is within the limits of other land snail species that are subdivided into subspecies.