The role of historic and climatic factors in the distribution of crustacean communities in Iberian Mediterranean ponds

Abstract

Summary We studied 140 freshwater ponds in eastern Spain spanning a wide range of water source, hydroperiod and regional heterogeneity attributable to orographic and climatic differences. Our aim was to provide a typology for Mediterranean ponds using crustacean assemblages and to find key environmental thresholds that define these pond types. To search for the environmental variables that define these communities, two complementary analyses were used: correspondence analyses (CA) and multivariate regression trees (MRT). We found a high level of specificity of crustaceans defining the different pond types. Three ponds, which were not associated with any of the large set of environmental variables used, were clearly separated from the rest in the CA. These held a very specific and probably relict community, characterised by the large calanoid Hemidiaptomus: we refer to these as ‘Hemidiaptomus’ ponds. Taxonomic information suggests a fundamental influence of historical events. The MRT analysis applied to the rest of the ponds allowed us to create a hierarchical order of several current environmental factors that account for their crustacean community composition. Thus, we defined four further pond types. The most important factor structuring communities was hydroperiod, separating temporary ponds, mainly fed by rain, from permanent ponds, fed from more stable sources. Climate‐related factors subsequently separated two groups of temporary ponds: (i) temporary ponds in semi‐arid areas (mean rainfall <600 mm year−1, spring rainfall <150 mm), which contained Neolovenula alluaudi and (ii) temporary ponds in semi‐humid areas, which contained Mixodiaptomus incrassatus. Amongst the permanent ponds, (iii) lowland coastal spring‐fed ponds with quite constant temperatures hosted a singular crustacean community that was well separated from that found in (iv) inland mountain ponds consisting of more ubiquitous crustaceans. These results provide a typology of ponds useful for conservation planning and freshwater biodiversity maintenance. Moreover, the identified ecological thresholds should be helpful in predicting the communities to be expected as a result of changes to land use or climate.