Disentangling structural and functional responses of native versus alien communities by canonical ordination analyses and variation partitioning with multiple matrices

Abstract

Freshwaters are under accelerated human pressure, and mollusk communities are among its most sensitive, threatened, and valuable components. To the best of our knowledge, the overall effects of damming, environment, space, time, and invasive alien mollusk species, on structural and functional responses of native mollusk communities were not yet compared. Using historical information and recent data from a river, we aimed to investigate and disentangle these effects and evaluate the differences in structural and functional responses of natives and alien invasives to the same predictors. Variation partitioning showed that alien species were as important predictors as were environmental factors and time in explaining species composition of native freshwater mollusk communities. Aliens were more independent of environmental conditions than natives and responded to different drivers, partially explaining their invasion success. The increased abundance of some alien gastropods was positively related to taxonomic diversity, while certain alien bivalves were negatively associated with the functional diversity of native communities. We introduce a cumulative variation partitioning with multiple response (native and alien) and predictor matrices, along with a diagram to show their relations, advocating for a conceptual shift in future community ecology, from “variables to matrices” and from “multivariate analyses to multi-matrix statistical modeling”.

Vegetation–edaphic correlation and importance value index in himalayan ‘ecotone’ temperate conifer forest using the multivariate technique

“…The findings demonstrated that environmental factors such as elevation, soil pH, temperature, and canopy cover were significant factors which constituted vegetation composition. Likewise, it also has been reported that these are key factors that significantly influence vegetation growth and distribution ( Ali et al, 2022 , Ali and Khan, 2022 , Sîrbu et al, 2022 , Chen et al, 2023 ). According to the CCA–ordination biplot, vegetation and topographic variables on axis 1 showed a significant correlation.…”

“…For quantifying the relationship between vegetation abundance, environmental variables, and edaphic factors, principal component analysis (PCA), redundancy analysis (RDA), and Canonical correspondence analysis (CCA) has been widely used ( Ali et al, 2022 , Ali and Khan, 2022 , Sîrbu et al, 2022 ). In order to determine the most influential variables, we performed CCA-ordination, which explained 68.5 % of the variance in the data.…”

Differences in trait–environment relationships: Implications for community weighted means tests

“…CWM‐sp). These methods include extensions of constrained ordinations, with predictors used for both the sites (environment) and for species (traits) as for example the popular fourth‐corner method and modifications of it (Dray et al, 2014; Dray & Legendre, 2008; Legendre et al, 1997; Sîrbu et al, 2022; ter Braak, 2012; Zelený, 2018), or the double‐constrained CCA (ter Braak, Šmilauer, et al, 2018). The fourth‐corner method, for example have been shown to provide the test with strongest power in the case of single linear trait effects on species distribution (Peres‐Neto et al, 2017; see also Section 4).…”