Biodiversity change in metacommunities, such as homogenization, is often measured using beta diversity metrics. However, other metrics can provide complementary information. Here we use spatial alpha (π°), beta (π±), gamma (π) and zeta (π) diversity to describe plant metacommunity development at successive time-periods over 12 millennia in a previously glaciated region, as applied to sedimentary ancient DNA data. We find that the metacommunity diversified (π±) and homogenized (π) over millennia, concurrently with an increase in the number of taxa (π° and π). The turnover of taxa between time-periods declined, with taxon appearance exceeding taxon disappearance in the communities. This suggests local co-existence of taxa increased. In contrast, the turnover of shared taxa (ΞΆ) among communities was continuously high, suggesting the regional metacommunity homogenization was largely transient. That plant communities homogenized but remained distinctively different over millennia highlights how individual communities are essential to maintain metacommunity biodiversity.
