Species richness drove selection of individuals within wetlands based on
traits related to acquisition and utilization of light
Abstract
Aim: Selection within natural communities has mainly been studied along
large abiotic gradient, while the selection of individuals within
population should occur locally under the play of biotic filter. To
better seize the role of the latter, we postulated that the hierarchal
nature of environmental selection and the multiple dimension of species
trait space needed to be accounted for. Methods: We replicated a natural
species richness gradient (from 2 to 16 species) within four contrasted
wetlands (bog, fen, meadow, marsh), sampling functional traits from
random individuals in communities. Developing a hierarchical
distributional modelling, we analyzed the variation of the mean and
dispersion of functional trait space at the ecosystem, community and
species levels. Key results: We found that the abiotic differences
between wetlands, which shaped a plant productivity gradient, selected
species in regards with their leaf nutrient conservation / acquisition
strategy. Within ecosystems, plant species richness was a strong driver
of trait variation among both communities and species. Among
communities, it shaped the selection of individuals according to their
space occupation and leaf adaptations to light conditions.
Demographically, some species used intraspecific trait variation to
maintain equally dense populations, while others used it to become
dominant in favorable conditions. Main Conclusions: Within ecosystems,
variation in biotic conditions selects individuals along functional
dimensions that are independent to the ones selected across ecosystems.
Because intraspecific variations of light-related traits are related to
demographic responses, it offers a way to link the study of species
richness and eco-evolutionary dynamics.