Metacommunity organization of tropical and mediterranean temporary ponds

Resumen

The metacommunity concept provides a theoretical framework to explain the distribution of organisms, encompassing processes acting at different spatial and temporal scales. Environmental selection and dispersal are key processes structuring metacommunities, acting with different intensities depending on the ecosystems or organisms studied. However, few general patterns seem to emerge in the various reviews and meta-analyses that have been carried out in this regard. In this thesis, we study the similarities and differences in how environmental, spatial and temporal effects structure metacommunities in tropical and mediterranean temporary ponds. Our results show that, despite environmental differences between ponds located in different regions, environmental heterogeneity may be similar. However, mediterranean ponds showed greater heterogeneity in limnological variables, which are considered more local, whereas tropical ponds showed higher climate heterogeneity, considered more regional, and spatially structured. We found more intense pure environmental effects in the mediterranean metacommunity, whereas the tropical metacommunity was more influenced by the spatially structured environment. These differences in the intensity of pure and spatially structured environmental effects could be related to differences in limnological and climate heterogeneity, higher in the mediterranean and tropical metacommunity, respectively. Pure spatial effects are more relevant in the tropical metacommunity, suggesting a greater dispersal limitation derived from more intense orographic (ecological) barriers in the tropics. These patterns are repeated in time throughout the same hydrological year. There are no patterns in these effects according to the dispersal ability of the organisms. Metacommunities of actively and passively dispersing organisms are structured similarly by environmental and spatial effects. However, differences between regions are more marked in active dispersers. Pure temporal effects are important, even as much as environmental effects, and especially in organisms with intermediate body size. These pure temporal effects are higher in the mediterranean metacommunity, possibly related to more variable successions over time. In addition, regional diversity in the tropical metacommunity was higher than in the mediterranean one. This was not caused by greater temporal variation in diversity, nor by a greater spatial heterogeneity of communities, but rather related to higher local diversity.