Seasonal abundance and spatio-temporal distribution of the troglophylic harvestman Ischyropsalis ravasinii (Arachnida, Opiliones, Ischyropsalididae) in the Buso del Valon ice cave, Eastern Italian Prealps

Abstract

We explore the population of the troglophilic harvestman Ischyropsalis ravasinii inhabiting the Buso del Valon ice cave located in the Italian Prealps. Spatial and temporal distributions of the specimens are investigated in relation to the variation of environmental abiotic conditions in the cave, such as the seasonal temperature and substrate surface typology. Our results show that I. ravasinii is distributed unevenly in the cave, most of individuals being present in the scree-covered section of the cave with superficial activities limited to the warm seasons only. In addition, our data suggests that the presence of a thick layer of rocky debris, together with high humidity and cold temperatures, are important limiting factors for the species. Seven additional species of harvestman are recorded in the cave, including the congeneric troglophilic species Ischyropsalis strandi. This is the first known record of these two troglophilic Ischyropsalis species coexisting within the same cave. An updated map of the distribution of I. ravasinii and I. strandi in the Italian Prealps is provided.