Search

A tenet of ecology is that temporal variability in ecological structure and processes tends to decrease with increasing spatial scales (from locales to regions) and levels of biological organization (from populations to communities). However, patterns in temporal variability across trophic levels and the mechanisms that produce them remain poorly understood. Here we analyzed the abundance time series of spatially structured communities (i.e., metacommunities) spanning basal resources to top predators from 355 freshwater sites across three continents. Specifically, we used a hierarchical partitioning method to disentangle the propagation of temporal variability in abundance across spatial scales and trophic levels. We then used structural equation modeling to determine if the strength and direction of relationships between temporal variability, synchrony, biodiversity, and environmental and spatial settings depended on trophic level and spatial scale. We found that temporal variability in abundance decreased from producers to tertiary consumers but did so mainly at the local scale. Species population synchrony within sites increased with trophic level, whereas synchrony among communities decreased. At the local scale, temporal variability in precipitation and species diversity were associated with population variability (linear partial coefficient, β = 0.23) and population synchrony (β = −0.39) similarly across trophic levels, respectively. At the regional scale, community synchrony was not related to climatic or spatial predictors, but the strength of relationships between metacommunity variability and community synchrony decreased systematically from top predators (β = 0.73) to secondary consumers (β = 0.54), to primary consumers (β = 0.30) to producers (β = 0). Our results suggest that mobile predators may often stabilize metacommunities by buffering variability that originates at the base of food webs. This finding illustrates that the trophic structure of metacommunities, which integrates variation in organismal body size and its correlates, should be considered when investigating ecological stability in natural systems. More broadly, our work advances the notion that temporal stability is an emergent property of ecosystems that may be threatened in complex ways by biodiversity loss and habitat fragmentation. [ABSTRACT FROM AUTHOR]

Aim: Contemporary dispersal constraints and environmental conditions are broadly recognized as significant drivers of beta diversity patterns. However, beta diversity patterns may also reflect the legacy of past climatic and geological events. In this study, we investigated the relative importance of historical and contemporary factors as drivers of taxonomic, functional and phylogenetic beta diversity in Neotropical stream communities. Location: The Colombian Orinoco basin. Taxon: Diatoms and insects. Methods: We estimated taxonomic, phylogenetic and functional beta diversity using Baselga's (BAS) and Podani's (POD) frameworks. Following both frameworks, we further partitioned every biodiversity facet into turnover and nestedness or richness difference components. Then, we used generalized linear models (GLM) to relate each biodiversity facet with environmental, spatial and historical factors. Results: We found that both historical and contemporary factors affected current patterns of beta diversity. Historical factors and water pH and temperature had the strongest effect on beta diversity patterns, particularly for taxonomic and phylogenetic facets. GLM models performed better for insects than for diatoms in all three facets. Within communities, our analysis also revealed a partial congruence between BAS‐ and POD‐based results. Main conclusions: Due to their past geological history and contemporary environmental gradients, tropical montane streams are natural laboratories for disentangling the joint effects of ecological and biogeographical factors on biodiversity patterns. Our study reveals that present‐day distribution patterns cannot be fully explained without accounting for the effects of past geological and climatic events on mountain landscapes. In the Neotropics, montane geology sets the stage for speciation and landscape formation, with which ecological (e.g., dispersal limitation) and environmental factors interact to generate spatial variation in species turnover. [ABSTRACT FROM AUTHOR]

Oviposition site selection by aquatic insects is usually influenced by both aquatic and terrestrial cues. Landscape changes (e.g. native vegetation loss) can affect the level of the reproductive success in aquatic insects, changing local species composition and richness.We investigate whether forest cover loss around streams influences the number of species with exophytic (species which lay eggs directly on the water surface), endophytic (species which lay their eggs directly into plant tissue), or epiphytic (species which lay eggs on the exposed surface of rocks, leaves, trunks or other substrates protruding from the stream surface) oviposition behaviour in dragonfly assemblages.We sampled adult dragonflies in 116 streams in a Neotropical savanna region in Brazil. The relationship between species richness for each behavioural category, and the proportion of forest cover around the streams, was tested using regression analysis.We collected 2413 dragonfly (Anisoptera and Zygoptera) individuals, belonging to 8 families, 30 genera, and 63 species. Of these, 25 species were classified as exophytic, 28 as epiphytic, and 10 as endophytic. Our results show that the number of species with exophytic or epiphytic behaviour was strongly related to riparian forest loss.Forest loss changes the habitat, and here, specifically changes site suitability for oviposition. We highlight the importance of using behavioural traits as a bioindicator tool for the assessment of anthropogenic impacts on tropical forest. [ABSTRACT FROM AUTHOR]