A Test for Competition for Food Among Adult Brachinus Spp. (Coleoptera: Carabidae)

E-ISSN： 1939-9170|67|6|1655-1664

ISSN： 0012-9658

Source： Ecology, Vol.67, Iss.6, 1986-12, pp. : 1655-1664

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Abstract

An experimental study of competition for food among adult Brachinus lateralis and Brachinus mexicanus was conducted at sites where B. lateralis was numerically dominant and where many individuals were underfed. By removing adult B. lateralis caught in pitfall traps, I reduced relative to controls the populations of B. lateralis by an estimated 33—35% after 10, and 45—47% after 15 removal episodes, with each removal episode 2—3 d after the previous one. An index of feeding success (condition factor) was used to assess the effect of removals on feeding rates of remaining B. lateralis and B. mexicanus. Jolly—Seber population estimates and catch per unit effort were used as indicators of a numerical response by B. mexicanus to removals of B. lateralis. After removals, there was no indication of increased feeding by remaining B. lateralis and B. mexicanus. No numerical response of B. mexicanus to removal of its congener was detected using either each per unit effort or Jolly—Seber population estimates. Thus, I could detect no competition for food among adults, despite demonstrated food shortage for these beetles. Food supply for these beetles does not seem to act as a density—dependent factor.