# Asynchrony Drives Plant and Animal Community Stability in Mediterranean Coastal Dunes
## 4 Discussion  
Diversity-stability relationship studies often focus exclusively on richness and stability, without considering the environmental factors or interspecific relationships that may drive stability [21]. We investigated the roles of species richness, environmental condition (perennial vegetation cover), synchrony, and weighted population variability in driving community variability across multiple taxonomic groups. Our empirical data consistently presented synchrony as the most strongly and positively correlated parameter for community variability (_CVcomm_) for all taxa. In addition, synchrony was a better predictor from community variability than weighted population variability, despite both parameters being mathematically linked to community variability [18]. In stability terms (as the inverse of variability), the asynchrony-community stability relationship was always significant and positive across all taxa; a high degree asynchrony appeared to confer more stable communities no matter which taxon and despite the different directionalities and strengths in the relationships among all other parameters. In contrast, a positive diversity-stability relationship (DSR) was only supported in rodents (a negative richness-_CVcomm_ correlation equates to a positive richness-community stability relationship). Figure 4: Linear regressions lm(Y-X\({}^{2}\)) for (**a**) annual plants, and lm(Y-X) for (**b**) beetles (**c**) rodents and (**d**) reptiles. Arrows are drawn from independent (X) to dependent (Y) for all significant regressions (* \(p<0.05\), ** \(p<0.01\), *** \(p<0.001\)); Adjusted R\({}^{2}\) values are given and patterns depict directions of correlation: Solid = positive-linear, dashed= negative-linear, dotted = U shaped unimodal, double-dashed = bell-shaped unimodal. Full regression outputs are given in Supplementary Materials Table S2. \(\bigstar\) Depicts the strongest (highest R\({}^{2}\)) positive correlation for each taxon and is presented in full in Figure 3e-h.  
Asynchrony has been recognized as a key driver in theoretical and modelled DSR [18; 24; 85]. In empirical studies, asynchrony can play a key role in stabilizing real plant communities in grasslands, but other studies had conflicting results [8; 21; 25; 26; 29; 86; 87]. Despite some of the founding theory of DSR being focused on fluctuations of animal populations [88; 89] few studies have looked at animal stability in relation to asynchrony. [PERSON] et al. [27] considered asynchrony in relation to community stability for plants, arthropods, birds, and bats, and found (as we did) a consistent positive relationship between asynchrony and community stability for animal and plant taxa in both grassland and forest systems. As with our findings, they too suggest that asynchrony was a stronger driver of community stability than richness directly. In terms of asynchrony and richness, several empirical studies have also reported a positive relationship in experimental [85] and naturally assembled grasslands [90], whereas [PERSON] et al. [27] reported the opposite for grassland plants. We found support for a positive asynchrony-richness relationship for beetles and rodents (i.e., a negative synchrony-richness correlation), whereas the asynchrony-richness relationship was negative for reptiles and unimodal for annuals. Asynchrony could be expected to increase with increasing richness due to processes such as niche partitioning at the evolutionary scale or competitive exclusion at the ecological scale [14; 18; 91]. The mechanisms for this relationship thus remain unclear. Asynchrony can reflect either heterogeneity in species (functional) responses to environmental conditions (response diversity), or simply their demographic stochasticity [8; 12; 27; 29; 32]. The degree to which asynchrony is linked to diversity has been shown to be influenced by environmental condition in both empirical [86; 90] and modelled [29] systems.