Phylogenetic relationship and plant life stage but not biogeographic history mediate priority effects of European grassland plants

Abstract

The timing and order of species arrival have been shown to be a significant factor in the assembly of biotic communities. Therefore, understanding priority effects, which refer to the impact of an early-arriving species on a later-arriving one, can help us better predict community assembly processes. However, little is known about the role of phylogenetic distance (PD) in priority effects and how they are mediated by the biogeographic history (BH) and the life stages (LSs) of interacting species. To shed light on the role of PD in priority effects, we conducted a multispecies greenhouse experiment. We created 10 allopatric and 10 sympatric species pairs, representing a PD gradient between early- and late-arriving species from 5 to 270 Myr in evolutionary history and tested the priority effect of early-arriving species on the late-arriving species at multiple LSs. We found evidence of stronger competition between closely related species, as late-arriving plants produced less above-ground biomass when the PD was low. However, priority effects varied across the development of late-arriving plants, as there were no effects on seedling emergence and survival, independent of PD. Regardless of PD, the pairs of allopatric and sympatric species did not differ in their responses. Synthesis. While many studies have produced contradictory results regarding the effect of PD on plant–plant interactions, our study provides experimental evidence that priority effects can be stronger when PD is small. This effect was independent of BH but varied across different LSs of late-arriving plants. The dependence of the effect of PD on the LS of late-arriving species highlights the importance of the timing of interactions for the assembly of plant communities, which could also have significant implications for the fields of invasion and restoration ecology.