Abstract
Metacommunities are dynamic systems, but the influence of time independently of environmental change in their configuration has been rarely considered. Temporary ponds are excellent ecosystem models, as they have well-defined boundaries in time and space; their communities are relatively isolated through a landscape matrix, and the progress of time leads to major changes through ecological succession and in habitat suitability related to hydroperiod dynamics. Therefore, strong temporal effects are expected to influence their metacommunity structure. We surveyed 30 temporary ponds along the dry tropical region of western Costa Rica and Nicaragua at three different moments of their hydroperiod: shortly after the infilling of the water bodies, at the middle of the hydroperiod and just before desiccation. We obtained data on 56 environmental variables (including limnological, climatic, landscape, hydrogeomorphological and conservation state), and used geographic coordinates to build spatial variables (Moran Eigenvector Maps). We collected biological samples and estimated the specific abundance of phytoplankton, zooplankton and benthic invertebrates. To evaluate the relative role of environmental, spatial and temporal (sequential sampling season) effects in metacommunity organization of the 646 species found, we used variation partitioning with distance-based redundancy analyses for each group of organisms. We repeated the analyses for selected taxonomic groups, separately for each sampling season, to check how the variance explained by spatial and environmental factors varied between sampling periods. The inclusion of time in the analysis highlighted that pure temporal effects explained part of metacommunity variance in almost every group, being as important as spatial or even environmental effects for some groups of organisms. In contrast to the assumed low environmental constraints in tropical areas (i.e. high and stable temperatures), we found strong environmental effects. Passive dispersers were more influenced by environmental factors than active ones. We also found a positive relationship between the body size of the different groups of organism and the magnitude of the temporal effect, interpreted as related to generation time. Finally, when analyzing each sampling period separately, we found differences in the relative role of environment and space at different sampling periods, showing that snapshot surveys may not be representative of highly dynamic metacommunities.
Highlights
The establishment of the metacommunity concept as referring to a group of communities linked by dispersal of their interacting species (Hanski and Gilpin, 1991; Wilson, 1992) prompted a turning point in understanding species distributions and abundances
We measured in situ water temperature, total dissolved solids (TDS), electric conductivity (EC) and pH using a Hanna pH/EC meter HI 98130; oxygen concentration was measured with the Winkler method and transparency with a Snell tube
We found 295 phytoplankton taxa, most of them identified to species level (Cyanobacteria: 44 taxa; Chlorophyceae: 114 taxa; mixotrophic phytoplankton: 56 taxa; Diatomea: 77 taxa), 102 rotifer taxa, most of them identified to species level, so as the 80 crustacean taxa (Branchiopoda: 34 taxa, Copepoda: 15 taxa, including 13 Cyclopoida and 2 Calanoida, Ostracoda: 31 taxa) and 169 macroinvertebrate taxa, including 19 mollusks, 34 paleopterans, 19 heteropterans, 28 coleopterans, and 32 dipterans (121 insect taxa)
Summary
The establishment of the metacommunity concept as referring to a group of communities linked by dispersal of their interacting species (Hanski and Gilpin, 1991; Wilson, 1992) prompted a turning point in understanding species distributions and abundances. Environmental filtering (the species sorting paradigm; Leibold et al, 2004), but other mechanisms related to spatial effects and dispersal rates, play a key role structuring metacommunities. Patch-dynamics (Levins and Culver, 1971), sink-source dynamics (or mass-effects; Holt, 1993) and neutral (Hubbell, 2001) paradigms are complementary to the species sorting approach when studying metacommunity assembly. In this framework, there is a temporal component that has seldom been considered when testing theoretical expectations with empirical data. Some traits such as generation time, type of dispersal or survival strategy toward desiccation may influence temporal dynamics, which in turn may strongly regulate metacommunity composition (Boix et al, 2004; Holt et al, 2005; Fernandes et al, 2014; Castillo-Escrivà et al, 2017c)
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