Priority determines tribolium competitive outcome in a food-limited environment

<p>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 <i>Tribolium</i> remains to be tested. The present study examined the importance of priority effects in competitions between two common species of flour beetle (Coleoptera: Tenebrionidae): <i>Tribolium castaneum</i> and <i>T. confusum</i>. To investigate whether priority effects confer competitive advantages to <i>Tribolium</i> beetles, relative introduction times of <i>T. castaneum</i> and <i>T. confusum</i> to competitive arenas were manipulated, and adult populations were measured for seven months. Four important patterns were noted: (1) <i>Tribolium</i> 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) <i>T. castaneum</i> benefited more from priority arrival than <i>T. confusum</i>, and (4) available bran resources largely predicted population decline in adult beetles toward the end of the experiment. These results suggest competitive outcome in <i>Tribolium</i> is not always predicted by species' identity, and that performance could instead be determined by the timing of species' arrivals and available resources.</p>