Phenological modularity in amphibian calling behaviour: Geographic trends and local determinants

Phenology of species, the coupling of vital activities to specific times of the year, plays a main role in ecosystem functioning and is expected to be affected by global change. We analysed the temporal structure of 52 amphibian communities in South America encompassing a latitudinal range from 7o to 34o south. Phenological modularity - species tendencies to aggregate along the months - is here introduced as a ubiquitous property of biodiversity architecture. Further, we identified an increase in phenological modularity with species richness, available energy and in communities with lower thermal dependence (i.e. the rate of change in the number of species active along the year associated with the environmental temperature). These patterns are in agreement with predictions derived from several ecological hypotheses: complexity-stability, species-energy and metabolic ecology. However, no direct association between modularity and the phylogenetic structure of communities was observed. A structural equation model that outperformed all the plausible alternative models considered supports these results. Modularity is reported here as a main feature of the phenology of communities that depends on environmental conditions. Here, we report for the first time a putative connection between community species richness and the degree of temporal structure - phenological modularity; the thermal dependence shows that communities at low latitudes are more vulnerable to climate change; energetic environments also promote communities with phenological modularity; and latitudinal patterns of phylogenetic community structure can give us clues of which species would be important to the conservation of community processes. These results call for further theoretical analyses to support the connection between phenological modularity, community stability and vulnerability to global change.