Millennia of metacommunity diversification and homogenization captured by sedimentary ancient DNA

Alpha (𝝰), beta (𝝱), gamma (𝛄), and zeta (𝛇) diversity metrics are complementary in their information, yet insight from this complementarity has yet to be explored. Here, we use postglacial lake sediments for reconstructing plant metacommunity diversity patterns using all four metrics. Based on sedimentary ancient DNA data, we find that the metacommunity both diversified (𝝱spatial) and homogenized (𝛇) over millennia of ecosystem development, alongside rising taxon richness at both community (𝝰) and metacommunity (𝛄) levels. In contrast, the temporal turnover of taxa (𝝱temporal) declined, both at the community and metacommunity level. With taxon appearances exceeding disappearances, this suggests the co-existence of taxa in the communities increased. However, the shared taxa in the metacommunity (ζ) showed a continuously high temporal turnover, suggesting the taxa contributing to the metacommunity homogenization were largely transient. That communities have homogenized but remained distinctively different over millennia highlights the importance of individual communities in sustaining metacommunity biodiversity.

Methods
The data used in this study was initially published by Rijal et al. 2021 and further updated by Alsos et al. 2022. The terrestrial plant data used in this study are available as the supplementary material in Alsos et al. 2022.