Abstract
Mountains influence species distribution through differing climate variables associated with increasing elevation. These factors determine species niche ranges and phenology. Although the distribution patterns of some specific insect groups relative to elevation have been determined, how differing environmental conditions across elevation zones differentially influence the phenology of various insect groups is largely unknown. This is important in this era of rapid climate change. We assess here how species composition and seasonal peaks in abundance among different insect pollinator groups and flowering plants differ across four floristically distinct elevation zones up a sentinel mountain subject to strong weather events. We sampled insect pollinators in four major groups (bees, wasps, beetles and flies) over two spring seasons. Pollinator species composition across all elevation zones tracks flowering plant species composition. In terms of abundance, beetles were the dominant group across the three lower zones, but declined greatly in the summit zone, where flies and bees were more abundant. Bee abundance peaked earlier than the other groups across all four elevation zones, where there were significant peaks in abundance. Bee abundance peaked earlier than flowering plants at the middle zone and slightly later than flowering plants at the base zone, suggesting a mismatch. We conclude that, while elevation shapes species distribution, it also differentially influences species phenology. This may be of great significance in long-term assessment of species distribution in sensitive mountain ecosystems.
Highlights
Drives high a bundance[21]
In a sensitive ecosystem like the Cape Floristic Region (CFR) of South Africa, where bee diversity matches plant diversity[22], high plant productivity may ensue when mass flowering is associated with high bee abundance in warm elevation zones
We asked the following: (1) How does elevation affect species abundance and richness of flowervisiting insects, and importantly, how does this differ among taxonomic groups? (2) Are there differences in species assemblages among taxonomic groups of flower-visiting insects in response to elevation shift? (3) Do differences in species assemblages of flower-visiting insects track those of flowering plants with increasing elevation? (4) How does elevation shape species phenology among flower-visiting insect taxonomic groups in terms of abundance peak periods?
Summary
Drives high a bundance[21]. In a sensitive ecosystem like the Cape Floristic Region (CFR) of South Africa, where bee diversity matches plant diversity[22], high plant productivity may ensue when mass flowering is associated with high bee abundance in warm elevation zones. Some studies have shown how bee diversity and composition are driven mostly by the indirect effect of climate change on temporal distribution of floral resources[23,24,25], yet there may be differences in species response influencing productivity across elevation zones. While most of the spatio-temporal studies addressing insect and plant diversity have been across latitudinal gradients[38], studies across elevation gradients have only recently been c onducted[16, 17]. We investigate this in the CFR, a Mediterranean-type ecosystem with a rich and complex topography across most of its expanse. We asked the following: (1) How does elevation affect species abundance and richness of flowervisiting insects, and importantly, how does this differ among taxonomic groups? (2) Are there differences in species assemblages among taxonomic groups of flower-visiting insects in response to elevation shift? (3) Do differences in species assemblages of flower-visiting insects track those of flowering plants with increasing elevation? (4) How does elevation shape species phenology among flower-visiting insect taxonomic groups in terms of abundance peak periods?
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