ABSTRACT Community ecologists now recognise the importance of simultaneously integrating spatial and environmental processes, together with functional traits and phylogeny to provide a more complete understanding of community responses to environmental conditions. Although a growing number of studies integrate these elements, few have looked at the community‐environmental relationship in highly dynamic ecosystems such as fluvial lakes. In this study, we used information on zooplankton functional traits and taxonomy‐based phylogeny within a joint species distribution modelling (JSDMs) framework to explore how crustacean zooplankton communities are organised across a heterogeneous submerged aquatic vegetation (SAV) bed of a large, shallow fluvial lake (Lake Saint‐Pierre, Québec, Canada). We also evaluated the consistency of our results over time by analysing samples of zooplankton collected over the span of three summers (2012–2014) at approximately 30 sites along the south shore of the lake. More precisely, we investigated how ecological processes shaped species co‐responses to SAV habitats and water conditions among years with different hydrological regimes. Of the 72 zooplankton taxa detected across sites and years, the dominant cladocerans were largely composed of macrophyte‐associated taxa that is, Bosminidae, Chydoridae and Sididae. Water depth and flow, chemical and trophic conditions, SAV and the abundance of filamentous algae were all found to be important drivers of zooplankton community variation. Albeit their relative importance changed over the years, spatial changes in trophic status (nutrients, chlorophyll a ), conductivity (calcium), dystrophy (DOC, water colour), water depth and water flow had a major influence on zooplankton niche dimensionality. Nevertheless, SAV was particularly important in explaining the environmental niche of larger zooplankton (Chydoridae and Sididae). The spatial variation in species niches was best reflected by functional traits linked to feeding and habitat types, and body size; that is, even though the taxonomic composition and species‐level responses changed over the 3 years of sampling, responses at the species trait‐level remained consistent, suggesting a repetition in functional patterns across time. The application of JSDMs helped highlight the extent to which traits can explain the variation among species in their responses to both water condition and SAV habitat. Our results show that spatial and temporal changes in environmental factors can have a major influence on zooplankton species niche dimensionality. However, we found a high inter‐annual variability in both the zooplankton taxonomic composition and in their specific responses to environmental factors. In contrast, the response of functional traits (feeding and habitat types, body size) to environmental gradients showed high consistency across years, highlighting the importance of considering functional traits to understand the responses of communities to environmental gradients. The consistency of species traits could enhance the resilience of communities to environmental changes. These results highlight the role of functional diversity in understanding zooplankton community structure. This study provides support to the idea that functional traits can explain the variation among species in their responses to environmental conditions. We therefore provide a new perspective on zooplankton community assembly in a highly variable system.
Bolduc et al. (Sun,) studied this question.