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Nestedness has been widely used to measure the structure of biological communities and occurs when species-poor sites contain subsets of species-rich ones. Here, we examine nested patterns across the macroinvertebrate assemblages of 91 ponds in Doñana National Park, Spain, and explore temporal variation of nestedness and species richness in 19 temporary ponds over 2 years with differing rainfall. Macroinvertebrate assemblages were significantly nested; both pond spatial arrangement and environmental variation being important in driving nested patterns. Despite the nested structure observed, a number of taxa and ponds deviate from this pattern (termed idiosyncratic), by occurring more frequently than expected in species-poor sites, or having assemblages dominated by species largely absent from species-rich sites. Aquatic adults of winged insects, capable of dispersal, were more highly nested than non-dispersing taxa and life-history stages. Idiosyncratic taxa were found in ponds spanning a wide range of hydroperiods, although nestedness was higher in more permanent waterbodies. Monthly sampling demonstrated a gradual increase of species richness and nestedness from pond filling to April-May, when the most temporary ponds started to dry. Although the degree of nestedness of individual pond assemblages varied from month to month, the overall degree of nestedness in the two study years was practically identical despite marked differences in hydroperiod. Our results suggest that differential colonization and environmental variation are key processes driving the nested structure of Doñana ponds, that macroinvertebrate assemblages change in a predictable manner each year in response to cycles of pond wetting and drying, and that connectivity and environmental variability maintain biodiversity in pond networks.

Macroinvertebrate assemblages of temporary ponds are ideal model systems to explore biodiversity patterns and metacommunity ecology. In addition, the study of the environmental variables driving such biodiversity patterns is essential in establishing proper guidelines for the conservation of the singular fauna of temporary ponds, especially since such ponds are vulnerable systems., We analysed the macroinvertebrate assemblages and environmental characteristics of 80 ponds spread across the Doñana National Park, SW Spain to (i) analyse macroinvertebrate β-diversity and metacommunity structure; and (ii) discern the main environmental and spatial drivers of these patterns., The pond network was highly heterogeneous as temporary ponds were highly variable. Macroinvertebrate β-diversity partitioning showed that species replacement made the greatest contribution to total β-diversity while the contribution of nestedness was small. The macroinvertebrate community structure and β-diversity were similarly driven by: electrical conductivity (and co-variables alkalinity, pH, and ion concentrations), plant richness (and the co-variable pond surface area), maximum depth, marsh, and coastal proximity as well as two spatial descriptors extracted from Moran's eigenvector maps. The spatial descriptors indicated that large interpond distances were involved, suggesting that species dispersal limitations only take place over long distances in the area., Those taxa that departed from the general nested pattern, termed idiosyncratic, significantly contributed to the maintenance of high pond network diversity through the species replacement and occurred within particular environmental conditions in the pond network., These results reveal that environmental heterogeneity and connectivity are key factors in the preservation of high macroinvertebrate diversity in nested pond networks with high numbers of idiosyncratic species. [ABSTRACT FROM AUTHOR]

Seasonal variation in macroinvertebrate assemblages usually is attributed to environmental variability, but this relationship is unclear in temporary ponds because they are highly dynamic across time. We assessed the influence of environmental variables and biotic interactions on macroinvertebrate community structure in 22 temporary ponds sampled monthly over 2 successive years that differed in rainfall. We hypothesized that abiotic and biotic variables would have different influences on macroinvertebrates having different dispersal abilities (capable of dispersal or not) and dietary modes (predaceous or not). Constrained Analysis of Principal Coordinates showed mainly seasonal influences on community assembly. During the filling phase, water-column total P (TP) and pH were important, whereas maximum depth, pH, electrical conductivity, and dissolved O2 were important during the aquatic phase. When ponds were close to desiccation, water-column electrical conductivity and TP and sediment organic matter were most influential. Predation by urodele adults occurred early in the inundation cycle and by urodele larvae when the ponds were close to desiccation. Negative species checkerboards (patterns of species noncoexistence) revealed that primarily competitive exclusion was in operation immediately after pond inundation, whereas competitive exclusion and habitat segregation were operating in tandem during the subsequent months. During the drying phase, general deterioration of environmental conditions and high pressure exerted by biotic interactions may trigger macroinvertebrate strategies to survive desiccation. Variability in pond characteristics allows macroinvertebrate species to assemble and disassemble in response to pond inundation-desiccation cycles and, thus, supports high biodiversity in the area. [ABSTRACT FROM AUTHOR]

Recent and increasing interest in temporary ponds as biodiversity reservoirs fosters our need to test sampling techniques for characterising their biological communities. We compared the efficiency of dip-netting to that of fyke nets in sampling the macroinvertebrate assemblage of a temporary pond in Doñana National Park (SW Spain). We sampled the pond at four different times-morning, afternoon, evening and night-distinguishing between deep and shallow zones. In our sampling, dip-netting captured a higher number of taxa, and higher abundances of individuals than fyke nets. However, both techniques captured exclusive taxa, not recorded with the other device. Fyke nets distinguished between nocturnal and diurnal macroinvertebrates, and hence are more appropriate to study macroinvertebrate diel activity. We detected nocturnal activity in Gerris thoracicus larvae, and adults of Colymbetes fuscus, Rhantus suturalis, Rhantus hispanicus and Hydrochara flavipes. Conversely, larvae of Sympetrum fonscolombei and Notonecta spp., and adults of Notonecta glauca were mainly diurnal. The overall diel activity pattern of the macroinvertebrate assemblage depended on the diel activities of their integrating taxa and stages. Although dip-netting was more appropriate to sample macroinvertebrate assemblages in different microhabitats, fyke nets better captured nocturnal and fast-swimming invertebrates. Consequently, the joint use of both sampling techniques would capture a better picture of the representative macrofauna of a temporary pond than either one on its own. [ABSTRACT FROM AUTHOR]

Macroinvertebrate assemblages of 22 temporary ponds with different hydroperiod were sampled monthly during a dry year (2005–2006) and a wet year (2006–2007). Coleopteran and Heteropteran adults were most abundant at the end of the hydroperiod, while Coleopteran larvae, mainly Dytiscidae, were mostly recorded in spring. Macroinvertebrate assemblages differed between study years. The shorter hydroperiod of ponds in the dry year constrained the length of the aquatic period for macroinvertebrates, and three distinct wet phases of community composition could be distinguished: filling phase, aquatic phase and drying phase. In the wet year, with a longer pond hydroperiod, five phases could be identified, with the aquatic phase differentiated into winter, early spring and late spring phases. Dispersers such as Anisops sardeus, Berosus guttalis or Anacaena lutescens were typical during the filling phase and Corixa affinis or Enochrus fuscipennis during the drying phase. The ponds with intermediate hydroperiod showed a similar composition (mainly dispersers) at the beginning and end of their wet period; this is not being seen in early drying or long hydroperiod ponds. A general pattern was detected, with similar variation between both years, which may be associated with the life histories of the macroinvertebrate taxa recorded. [ABSTRACT FROM AUTHOR]