Distribution of Terrestrial Cave-Dwelling Arthropods in Two Adjacent Prealpine Italian Areas with Different Glacial Histories

The aim of this study was to investigate the distribution of cave-dwelling arthropod communities in 2 adjacent karst areas with different glacial histories. Endemic and obligate cave-dwelling faunas were recorded in 60 caves located in 2 adjacent Prealpine areas (in Veneto, northeastern Italy): the Baldo and Lessinia Mountain groups were compared. During the last glacial period, the Baldo Mountain group was completely surrounded and isolated from the Lessinia group by the Adige glacier, while the Lessinia was only partially surrounded. The effect of glacial isolation, both geographically (cave locations) and elevationally (cave elevation), on the faunal distribution was tested using the number of troglobiont and endemic species collected in each area. The Lessinia hosts a higher number of troglobiont species and a lower number of endemic species compared to those of the Baldo area. Furthermore, results indicated that the similarity in species assemblages in caves was not driven by their geographic location, but by colonization patterns caused by isolation created by the Adige glacier during the last ice age. This suggests that the geographic isolation of the Baldo area during Quaternary climatic fluctuations determined the species which colonized the caves and consequently prevented multiple colonizations during warm periods. Glacier-induced isolation during the last ice age can therefore be considered one of the main factors which determined terrestrial arthropod colonization of caves in the Prealps area.