Random ecological networks that depend on ephemeral wetland complexes

Abstract

Wetlands provide diverse ecosystem services: they create habitats, provide hydrological control, and regulate biogeochemical cycles of flora and fauna through interaction with surrounding wetlands. These services vary temporally, depending primarily on hydro-climatic conditions and the type of wetland. To better understand the functions of wetlands, it is necessary to analyze the effect of stochastic hydro-climatic conditions on the dynamics of wetland surface area and the resulting dispersal of species. In this study, we analyzed the dynamics of the connectivity and efficiency of ecological networks according to (1) the characteristics of the wetland area distribution, which varies by season, and (2) dispersal models (threshold distance, exponential kernel, and heavy-tailed movement). The results indicate that hydrologically sensitive small wetlands were often the primary elements that characterize wetland area distribution. Consequently, during dry seasons, the corresponding ecological network topology, measured by mean degree, network efficiency, and clustering coefficient decreased in all dispersal models we tested. We also found that while the correlation of hubs between dispersal models was strong, the levels of network vulnerability, evaluated by removing those hubs, were different, with the heavy-tailed model showing the highest vulnerability. Moreover, we observed the possibility of regime shift in ecological networks when a chronic, high dryness induced significant reduction of large wetlands. Our network modeling approach based on hydrologic systems will provide a new decision-making process and perspectives for conservation and restoration planning including the conditions regarding climate change.