# Asynchrony Drives Plant and Animal Community Stability in Mediterranean Coastal Dunes
## 1 Introduction  
Substantial evidence has demonstrated that diversity stabilizes ecosystem functioning over time [1, 2, 3, 4, 5, 6, 7]. Meanwhile, the current degradation of ecosystems and resultant losses of biodiversity reported globally could be reducing the capacity of ecosystems to maintain stable levels of function and productivity [4, 8, 9, 10, 11]. Thus, understanding the drivers of temporal stability has become critically important for conserving biodiversity and ecosystem function. Diversity-stability relationship (DSR) theories suggest that species richness can contribute to community stability through various mechanisms, such as statistical averaging [12], overyielding [4], species asynchrony and other species interactions [3, 4, 13, 14, 15, 16, 17, 18]. Nevertheless, species-rich communities may be more susceptible to disruption of key interactions and could, therefore, be less stable at the population level [7, 19, 20]. Community stability can be modelled as a function of species population stability weighted by their dominance, and the covariance (synchrony) between species [18]. The relative importance of different facets of biodiversity underlying the diversity-stability relationship remains unclear [21]. Asynchrony has played a key part in theoretical studies to predict DSR in modelled communities [4, 18, 22, 23, 24, 21]. Yet only a handful studies haveinvestigated the relationship between asynchrony and stability empirically [21; 25; 26; 27]. The dominance of a species is also likely to affect its contribution to overall stability [26; 28; 29]. Weighted population stability and asynchrony should therefore both affect community stability. We investigate the balance between them in the context of DSR. Stability cannot be understood outside the context of the environmental condition, and examining DSR in real -world ecosystems has been recognized as a key research need in ecology [30; 31; 32]. Yet most empirical studies of DSR focus on controlled, short-term, and small-scale experiments, under standardized environmental conditions with constant community composition, often only considering the role of species richness in driving community stability [27; 33]. Empirical support for the DSR in natural terrestrial ecosystems comes overwhelmingly from plants in grasslands and trees in mixed forests, due to the relative simplicity of the communities in these habitats [8; 34; 35; 36; 37]. The insights gained in considering cross-taxon congruence have been highlighted in a range of studies, from the effect of spatial heterogeneity on species distributions (e.g., [38; 39], to anthropogenic disturbance and fragmentation on species composition [40; 41; 42], and functional diversity [43]. Nevertheless, few studies examine multiple taxa in natural systems in the context of DSR [27]. Studying stability in natural systems and across multiple taxa is challenging. Data from Long-Term Ecological Research (LTER) networks (see [[https://www.ilter.network/accessed](https://www.ilter.network/accessed)]([https://www.ilter.network/accessed](https://www.ilter.network/accessed)) on 28 June 2021) help to overcome this challenge [8; 36; 44; 45]. We take advantage of a multi-taxa coastal dune LTER site with a natural gradient of increasing perennial vegetation to examine the mechanisms through which environmental condition and richness could affect the community stability of four taxonomic groups. Coastal dune systems provide a convenient system for studying the impact of environmental gradients on DSR because they are highly dynamic, relatively simple in terms of species diversity and complexity, and for Mediterranean coasts, most species are well documented [46]. In addition, coastal dunes are subject to a gradient of disturbance and stress, coupled with increasing perennial Plant Cover (PPC), and disturbance has been shown to affect plant and animal community stability [47; 48; 49; 50].