The diversity and distribution of introduced plant species reflects eight thousand years of settlement history

Human population has affected natural ecosystems since prehistoric times in many ways, causing disturbances in existing ecosystems and creating novel habitats, and altering the colonisation and extinction rates with potentially long-lasting effects on biodiversity. Here, we explored the pervasive effects of past human occupancy on present-day diversity and the distribution of plant species introduced by humans in the distant past – archaeophytes – at the regional spatial scale. We analysed spatial relations between the present-day species richness of archaeophytes and native flora, the environmental setting, archaeological evidence, and the relationship between the residence time of archaeophytes and their regional range size. We used fine-scaled gridded information on plant diversity and archaeological records for the period 6000 BCE to 1000 CE summarised as average occupancy probability (AOP) in Czechia, Central Europe. The proportion of archaeophytes in local flora positively correlated to AOP. Variation partitioning revealed largely overlapping effects of AOP, environmental conditions, and present-day land use on the relative diversity of archaeophytes in local flora. The relationship between the minimum residence time of introduced species and their regional range size was weak and non-significant.

Synthesis. Our results suggest that the present-day regional diversity of archaeophytes mirrors the intensity of past human settlement. However, the main underlying mechanism is the dispersal and environmental filtering of non-native species pools, while dispersal limitation plays a minor role in the regional patterns of archaeophyte diversity.