Functional differences stabilize beetle communities by weakening interspecific temporal synchrony

Abstract

The temporal stability of communities is essential for the maintenance of ecosystem functioning across trophic levels. The stabilizing effect of biodiversity is, among other factors, modulated by the level of synchrony in population fluctuations among the species in the community. What drives community synchrony, however, remains largely unclear. Community synchrony can be affected by external drivers such as disturbances, but also by the properties of the community. Species with different ecological strategies should fluctuate less synchronously than more similar species; thus, an increase in diversity of ecological strategies should decrease synchrony, and increase the stability of the community. Here, using an exceptionally large data set of ground beetle trappings in Dutch heathlands (~370,000 individuals in 19 plots, each sampled between 9 and 36 yr), we assess the drivers of community stability and synchrony, and their relationship with disturbance, species richness, and functional diversity (FD). We found no effect of disturbance (fire and topsoil removal) on community stability or synchrony, probably because of unpredictable patterns of increase or decrease of the populations. Community synchrony was overall positive, giving more support for independent and positive correlation between species than for compensatory dynamics. Synchrony decreased with increasing FD, but not with species richness. Supporting this, we found that the more species pairs differ in their traits, the less synchronously their populations fluctuate, where 74% of all pairs showed no significant correlation. Significant positive synchrony (19% of species pairs) was concentrated among pairs with low trait dissimilarity, and the 7% of pairs with significant negative temporal correlation showed no relation with pairwise functional dissimilarity. The stabilizing effect of FD via decreased synchrony supports largely untested theoretical expectations that an increased diversity of functional strategies in a community will have a stabilizing effect on community abundance. We hypothesize that because competition is low in this community, the stabilizing effect of FD reflects interspecific variation in responses to environmental fluctuations rather than competition.

Diversity of response and effect traits provides complementary information about avian community dynamics linked to ecological function

“…Our results show that communities of seed dispersers with high response trait diversity have more stable total community abundance over time, in line with predictions of the insurance hypothesis (Yachi & Loreau, 1999). Most existing support for this hypothesis has been found in synthetic plant communities, often at small spatial scales (Allan et al, 2011;Pillar et al, 2013;Craven et al, 2018;van Klink et al, 2019, but see Wilcox et al, 2017. Our finding that response trait diversity in assemblages of wild birds can predict stability in a property linked closely to ecosystem function suggests that the insurance hypothesis applies more generally and at larger spatial scales, with implications for how functional diversity metrics are F I G U R E 3 Relationships between the mean total community abundance of seed dispersers and functional dispersion (F DIS ) of effect traits (a), all traits (b) and F DIS response traits (c).…”

Functional trait effects on ecosystem stability: assembling the jigsaw puzzle

“…Constancy in ecosystem functioning can be obtained when 'inconstant' populations of species with similar effect traits periodically (for example, on a yearly basis) 'compensate' for each other (scenario 2, in Figure 2), that is, they negatively covary in time (antisynchrony). As we discussed earlier, theoretical [11] and empirical evidence [3,[58][59][60][61] suggests that antisynchrony will occur between species with different response traits, moderate to high ΔTPD R , and overall high functional diversity in a community; case 1 in Figure 2), reflecting different environmental preferences. Constancy in ecosystem functioning will then occur only if effect traits and response traits are dissociated (high functional diversity in response traits, low in effect traits).…”

“…As such, an increase in community functional diversity (Box 3) should lead to greater constancy. Support for a decrease in synchrony with increasing functional diversity has been found in beetle communities [61] and in manipulated plant communities [55,62]. The recent study by Craven et al [17] failed to detect any marked effect of plant functional diversity, expressed only for the leaf economics spectrum, on synchrony, but detected an effect of phylogenetic diversity, as in Cadotte et al [63].…”

“…The recent study by Craven et al [17] failed to detect any marked effect of plant functional diversity, expressed only for the leaf economics spectrum, on synchrony, but detected an effect of phylogenetic diversity, as in Cadotte et al [63]. This is possibly because the relationship between pairs of species and their synchrony is better appreciated on the basis of multiple traits [3,61]. Phylogenetic diversity can be considered as a proxy of multi-trait diversity and unmeasured traits [64].…”

Spatial heterogeneity in temporal dynamics of Alpine bird communities along an elevational gradient

“…Although resource availability seems to play a central role in regulating species responses and how they fluctuate in relation to the rest of the community, intrinsic properties of assemblages can also have influence on the level of community‐wide synchrony. For instance, according to theory‐based expectations (Morin et al, 2014), taxa with different ecological strategies should fluctuate less synchronously than more similar taxa; however, the relationship between functional diversity and community synchrony have been barely explored (but see Klink et al., 2019). Hence, it is likely that low functional originality and functional divergence in forest assemblages (García‐Navas et al., 2020) contribute to the concordance of species responses to environmental fluctuations (e.g.…”