Priority determines tribolium competitive outcome in a food-limited environment

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.