Asynchrony among insect pollinator groups and flowering plants with elevation

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.

Figure 1

Mean insect abundance (± SE) among elevation zones. Bars with common letters are not significantly different at p > 0.05.

Figure 2

Mean flower abundance (± SE) among elevation zones. Bars with common letters are not significantly different at p > 0.05.

Figure 3

Abundance of flower-visiting insects at the (a) base zone, (b) middle zone, (c) high zone, and (d) summit zone among taxonomic groups. Taxa with common letters are not significantly different at p > 0.05.

Figure 4

Species richness of flower-visiting insects at the (a) base zone, (b) middle zone, (c) high zone, and (d) summit zone among taxonomic groups. Taxa with common letters are not significantly different at p > 0.05.

Figure 5

Abundance of insect taxa and flowering plants across sampling days in the (a) base zone, (b) middle zone, (c) high zone, and (d) summit zone. Lines represent the best models for and the dots represents abundance recorded at each sampling period.

Figure 6

Canonical analysis of principal coordinate showing differences in (a) flower visiting insect species composition, and (b) flowering plant species composition across elevation zones. CAP plot was computed using Bray-Curtis similarity index obtained from the square-root transformation of abundance data.

Figure 7

Canonical analysis of principal coordinates, showing differences in species composition of (a) bees, (b) beetles, and (c) wasps across elevation zones. CAP plot was computed using Bray-Curtis similarity index obtained from the square-root transformation of abundance data.