The factors determining gradients of biodiversity are a fundamental yet unresolved topic in ecology. While diversity gradients have been analysed for numerous single taxa, progress towards general explanatory models has been hampered by limitations in the phylogenetic coverage of past studies. By parallel sampling of 25 major plant and animal taxa along a 3.7 km elevational gradient on Mt. Kilimanjaro, we quantify cross-taxon consensus in diversity gradients and evaluate predictors of diversity from single taxa to a multi-taxa community level. While single taxa show complex distribution patterns and respond to different environmental factors, scaling up diversity to the community level leads to an unambiguous support for temperature as the main predictor of species richness in both plants and animals. Our findings illuminate the influence of taxonomic coverage for models of diversity gradients and point to the importance of temperature for diversification and species coexistence in plant and animal communities.
Abstract. Diptera are one of the three largest and most diverse animal groups in the world. As an often neglected but important group of pollinators, they play a significant role in agrobiodiversity and the biodiversity of plants everywhere. Flies are present in almost all habitats and biomes and for many medicinal, food and ornamental plants, pollinating flies guarantee or enhance seed and fruit production. They are important in the natural landscape, in agriculture and in greenhouses, and have recently come into use in the production of seeds for seed banks. The Sao Paulo Pollinator Initiative, the CBD, and Pollinator secretariats were important starting points in the international recognition of pollinator importance. However, large gaps in our knowledge of the role of Diptera in pollination networks need to be addressed in order to sustain agriculture and to enable appropriate responses to climate change. At this 9th Conference of the Parties we would like to draw attention to the role of often-neglected Dipteran pollinators, to stress their current importance and potential future, use as pollinators in agriculture. A case study on flower flies that act as important pollinators, as adults, and major biocontrol agents, as larvae, illustrates their double importance for agriculture.
Diptera are important flower visitors and pollinators for many plant species and in a variety of habitats. Although Diptera are not as well studied as other groups of pollinators, there is a growing literature that we review here about the ecology of their foraging behaviour and their effectiveness as pollinators. We consider (1) how their foraging is constrained by the interaction among body size, colour, and environmental factors such as temperature, humidity, wind, and light; (2) what is known about their foraging at scales ranging from their movements between flowers on a plant, between individuals in a population, and among species in a community (i.e., constancy); and (3) the evidence for effects of intra- and interspecific competition on foraging. We conclude with a discussion of the effectiveness of Diptera as pollinators. The available data suggest that Diptera exhibit many of the same foraging behaviours as other flower visitors and that they are effective pollinators in both natural and agricultural ecosystems.
Reports of declines in biomass of flying insects have alarmed the world in recent years. However, how biomass declines reflect biodiversity loss is still an open question. Here, we analyze the abundance (19,604 individuals) of 162 hoverfly species (Diptera: Syrphidae), at six locations in German nature reserves in 1989 and 2014, and generalize the results with a model varying decline rates of common vs. rare species. We show isometric decline rates between total insect biomass and total hoverfly abundance and a scale-dependent decline in hoverfly species richness, ranging between −23% over the season to −82% at the daily level. We constructed a theoretical null model to explore how strong declines in total abundance translate to changing rank-abundance curves, species persistence, and diversity measures. Observed persistence rates were disproportionately lower than expected for species of intermediate abundance, while the rarest species showed decline and appearance rates consistent with random expectation. Our results suggest that large insect biomass declines are predictive of insect diversity declines. Under current threats, even the more common species are in peril, calling for a reevaluation of hazards and conservation strategies that traditionally target already rare and endangered species only.
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