Priority determines Tribolium competitive outcome in a food-limited environment.

Zane Holditch,Aaron D Smith

doi:10.1371/journal.pone.0235289

Abstract

Flour beetles are a classic model system for studying competitive dynamics between species occupying the same ecological niche. Competitive performance is often interpreted in terms of biological species traits such as fecundity, resource use, and predation. However, many studies only measure competitive ability when species enter an environment simultaneously, and thus do not consider how the relative timing of species’ arrival may determine competitive outcome (i.e., priority effects). Whether priority effects may influence competition in Tribolium remains to be tested. The present study examined the importance of priority effects in competitions between two common species of flour beetle (Coleoptera: Tenebrionidae): Tribolium castaneum and T. confusum. To investigate whether priority effects confer competitive advantages to Tribolium beetles, relative introduction times of T. castaneum and T. confusum to competitive arenas were manipulated, and adult populations were measured for seven months. Four important patterns were noted: (1) Tribolium species given two-weeks priority access to experimental arenas attained larger populations than their late-arriving competitor, (2) when founding adults were introduced simultaneously, T. castaneum was competitively dominant, (3) T. castaneum benefited more from priority arrival than T. confusum, and (4) available bran resources largely predicted population decline in adult beetles toward the end of the experiment. These results suggest competitive outcome in Tribolium is not always predicted by species’ identity, and that performance could instead be determined by the timing of species’ arrivals and available resources.

Highlights

Tribolium flour beetles (Coleoptera: Tenebrionidae) are excellent model organisms for testing hypotheses in genetics and population ecology [1,2,3], especially ecological competition
Priority determines Tribolium competitive outcome competitive performance is not intrinsic to a species, and that the outcome of interspecific competition depends upon the initial conditions of an ecological space
In the present study, timing of arrival was manipulated in competitions between T. castaneum and T. confusum

Summary

Introduction

Tribolium flour beetles (Coleoptera: Tenebrionidae) are excellent model organisms for testing hypotheses in genetics and population ecology [1,2,3], especially ecological competition. Priority determines Tribolium competitive outcome competitive performance is not intrinsic to a species, and that the outcome of interspecific competition depends upon the initial conditions of an ecological space. Early-arriving species often experience reduced competitive pressures compared to late-arriving species [13], and so some species appear to have evolved asynchronous breeding times to delay the onset of direct competition [10]. When individuals benefit from early-arrival (i.e., “priority effects”), competitive performance appears to be determined by both the relative order of arrival and the amount of time between the arrivals of the interacting species [14,15,16,17]. Priority effects appear to mediate interspecific competition in many systems including plant communities [18], ectomycorrhizal fungi [19], and insects [20,21,22]. Despite the importance of Tribolium beetles in competition research, priority effects in this system have not been measured

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