Determining the mechanisms that influence species composition in communities is a key question within the field of community ecology. Potential mechanisms can range from stochastic to deterministic, with communities likely experiencing some degree of both. Strong stochastic factors are predicted to lead to high diversity in species presence between communities (i.e. spatial beta diversity), while strong deterministic factors are predicted to lead to low species diversity between communities with similar environments. Traditionally, research on beta-diversity has focused on species, but the mechanisms driving patterns in species diversity should ultimately be mediated by species’ traits. In this study we use a time series natural predation gradient in pond communities to determine how the trait diversity in prey communities changes across space and time and whether this pattern is consistent with species level patterns. Specifically, we focused on odonate larvae which were sampled each season for 4 years in 49 ponds that exhibited a range of predation strength depending on the top predator. We then focused on twelve morphological trait values for each odonate species to determine how abundance weighed mean traits and functional trait diversity differed across sites (spatial beta diversity), seasons, and years (temporal beta diversity).
Results/Conclusions
The mean and variance in functional traits varied considerably among ponds, seasons, and year, and the variation was different across the predation gradient. Weak and strong predation were associated with a lower dispersion of trait values, while the largest dispersion was found at the intermediate predation level. These results suggest predation plays an important role in the assembly of trait composition in prey communities. Furthermore, the differential dispersion of traits depending on the top predator demonstrates that the level of predation is related to its strength as a habitat filter. The lower dispersion found under weak predation may be due to an increase in competitive pressure acting as an alternative habitat filter on prey traits. This study further elucidates the complex role predation has on influencing the diversity found in natural communities.