From local to regional: Assessing the spatial extent and regional representativeness of Holocene mollusc assemblages in Central Europe

Terrestrial mollusc assemblages are an important Quaternary proxy due to their local deposition and their usefulness for detailed habitat reconstruction; however, it is uncertain whether single or limited number of assemblages provide reliable information about larger spatial scales. In this paper, we report Holocene mollusc assemblages from four regions of Central Europe to determine the number of profiles required for a reliable assessment of past regional biodiversity. The study regions span a range of different geomorphological and environmental conditions, and show varied histories of human impact. For each study region, we examined the proportion of the modern species pool represented by different numbers of Holocene profiles. Our results indicate that while a single Holocene profile captures a significant proportion of local diversity, multiple profiles are required for broader regional studies or palaeoecological reconstructions. In addition, we assessed the spatial extent that a single Holocene profile most accurately represents by comparing the assemblages recorded in the profile with modern communities at varying distances from the profile. Our findings show that the profiles are generally most representative of areas within a few kilometres. However, this distance is significantly influenced by local topography, which is reflected in the size of the profile catchment area.