Release from interspecific competition results in species niche expansion in bumble bees Open Access

Atalla, Laila Melia (2016)

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Recently, there has been increasing attention in ecology to the importance of intraspecific variation resulting in individual specialization. Such specialization, which can be addressed in terms of dietary niche width, is especially important in pollinators, given that pollination has intense effects on ecological and evolutionary functioning. While previous work has demonstrated decoupled changes in niche width at the individual and species levels following release from interspecific competition, few field experiments have addressed the effects of ecological release on pollinators at multiple organismal levels. Here, we present a field experiment to test the effects of release from interspecific competition on niche breadth and specialization in bumble bees (Hymenoptera: Bombus), a critical clade of pollinators for both unmanaged and agricultural ecosystems. We conducted species removal experiments and observed the foraging behavior of individual bumble bees in order to assess the hypothesis that reduced interspecific competition leads to decoupled changes in bumble bee specialization and niche width at the individual, species, and guild levels. We found evidence of species niche expansion following release from interspecific competition, with important implications for pollination given ongoing bumble bee population declines.

Table of Contents

Introduction. 1

Materials and Methods. 4

Field Sites. 4

Species Removal Experiments. 5

Measuring Niche Breadth. 5

Quantifying Niche Breadth and Specialization. 6

Statistical Analyses. 7

Results. 8

Individual-Level Effects of Release from Interspecific Competition. 12

Species-Level Effects of Release from Interspecific Competition. 12

Guild-Level Effects of Release from Interspecific Competition. 13

Effects of Species, Tongue Length, and Guild Composition. 13

Discussion. 14

References. 17

Non-Print Sources. 19

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