How does trait variance partitioning help us to understand plant community assembly? The example of pond communities in the Kerguelen Islands

QuestionIn the current context of biodiversity erosion, functional approaches to the examination of community assembly mechanisms and better prediction of plant species fates have emerged. The assessment of trait variation patterns should be a powerful means of identifying community assembly mechanisms. However, most studies of trait variations and their consequences for individual performance (i.e., vegetative biomass) are usually incomplete as they focused on single ecological scales or filters, with no consideration of relationships between traits. Such research has provided a fragmented view of plant community assembly.LocationWe examined macrophyte communities living in ponds of the sub-Antarctic Iles Kerguelen.MethodsWe measured traits related to resource acquisition and conservation in all occurring species, and examined their variation across temporal (years), spatial (sites), and taxonomic (between and within species) scales and in response to multiple abiotic and biotic habitat variables. The consequences of these trait variations and the effects of their correlation for plant individual performance were also explored.ResultsTrait distributions were fairly conserved among sites, whereas we observed a large amount of intraspecific trait variation enabling individuals to resist filters. Responses to biotic and/or abiotic variables were trait-dependent, and simultaneous trait responses should enable individual plants to face several simultaneous constraints. Almost all traits had direct or indirect effects on individual performance, indicating the need to consider trait relationships.ConclusionThe partitioning of trait variance is a relevant approach to the identification of the scale at which the most decisive processes for plant community assembly operate without the interference of scale dependency issues, and should orient further research. In addition, several biotic and abiotic variables should be considered in future studies to better understand the effects of environmental changes on plant communities. We focused on the macrophyte communities living in the ponds of the Iles Kerguelen (sub-Antarctic region). Partitioning trait variance allows to detect at which scale the decisive processes operate in plant community assembly. In addition, we simultaneously considered biotic and abiotic variables to better understand the effects of environmental variations on traits, subsequently impacting plant performance and species fate.image