Abstract
In the current context of biodiversity erosion, functional approaches
have emerged to study community assembly mechanisms and to better
predict the fate of plant species. Assessing patterns of trait variation
should be a powerful tool to determine community assembly mechanisms.
Yet, studies on trait variations and their consequences on individual
performance are usually incomplete as they focus on a single ecological
scale or filter, and do not include relationships between traits,
resulting in a fragmented view of plant community assembly. We focused
on the macrophyte communities living in particular freshwater ecosystemsi.e. the ponds of the Iles Kerguelen, in the sub-Antarctic
region. We measured different categories of traits (aerial, root, and
clonal) on all occurring species to study trait variations across years,
sites and phylogeny scale (between species and within species), and in
response to multiple habitat abiotic and biotic variables. The
consequences of these traits variations and the effects of their
correlations for plant individual performance were also explored. Our
results first highlighted a filter operating on the overall distribution
of trait values within the region, whereas we observed a high amount of
intraspecific trait variation allowing individuals to better resist to
filters. Second, traits responses to biotic and/or abiotic factors were
trait-dependent, and this combination of simultaneous trait responses
should allow the plant as a whole to face several simultaneous
constraints. Lastly, almost all traits have either direct or indirect
effects on individual performance. As a conclusion, partitioning trait
variance is a relevant approach to detect at which scale operate the
most decisive processes in plant community assembly without scale
dependency issues, and then orient further researches. Furthermore, we
plead to consider multi-traits approach, and several biotic and abiotic
variables in future studies to better understand the effects of
environmental changes on plant communities.
Keywords : Functional traits, plant performance, variance
partitioning, intraspecific trait variability, macrophyte