Ecological relations among first-stage larvae of four species of Protostrongylidae (Nematoda) within their ovine host.

Competitive relations between protostrongylid nematodes parasitic in the ovine lung, using competition coefficients and asymptotic densities showed that two relatively scarce species (Neostrongylus linearis and Protostrongylus rufescens) exert strong competitive actions on the two most abundant species (Cystocaulus ocreatus and Muellerius capillaris). P. rufescens could lead to the disappearance of the more abundant species, if other compensatory factors did not exist in their life cycle.