Effects of a tapeworm parasite on the competition of Tribolium beetles

• Published in: Ecology (Durham) 1998-04, Vol.79 (3), p.1093-1103
• Main Authors: Yan, Guiyun, Stevens, Lori, Goodnight, Charles J., Schall, Joseph J.
• Format: Article
• Language: English
• Subjects: Analysis; Animal and plant ecology; Animal, plant and microbial ecology; Beetles; Biological and medical sciences; BIOLOGICAL COMPETITION; coexistence; COMPETENCIA BIOLOGICA; Competition; COMPETITION BIOLOGIQUE; DEPREDACION; Ecological competition; Ecology; Environmental aspects; Fundamental and applied biological sciences. Psychology; Helminths; HOST PARASITE RELATIONS; Host-parasite relationships; HYMENOLEPIS DIMINUTA; INFECTIONS; Insect eggs; Insects; INTERSPECIFIC COMPETITION; INTRAGUILD PREDATION; parasite; Parasite hosts; Parasites; Parasitism; PATHOGENESE; PATHOGENESIS; PATOGENESIS; Population density; PREDATION; RELACIONES HUESPED PARASITO; RELATION HOTE PARASITE; Species extinction; Synecology; Tapeworms; Terrestrial ecosystems; Tribolium; TRIBOLIUM CASTANEUM; TRIBOLIUM CONFUSUM; Worms, Intestinal and parasitic
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/0012-9658(1998)079[1093:EOATPO]2.0.CO;2

The effect of parasites on host community structure and biodiversity is an important issue of community ecology. Both verbal and mathematical models suggest that host species with higher fitness costs associated with parasitism should bear a competitive disadvantage in the presence of parasites. However, few rigorous empirical tests exist. This study examined the effects of a tapeworm parasite (Hymenolepis diminuta) on competition between two flour beetle species (Tribolium confusum and T. castaneum). The flour beetles are the intermediate host of this rat tapeworm parasite. Previous studies demonstrated that T. castaneum is usually the superior competitor in competition with T. confusum in parasite-free environments. However, because T. castaneum is more susceptible to parasitism and shows higher fitness costs when infected than T. confusum, we expected that T. castaneum would bear a competitive disadvantage in the presence of the parasite. In contrast, we found that tapeworm infection significantly increased the likelihood of T. castaneum winning the competition, reduced the time needed for T. castaneum to win, and increased T. castaneum population density compared to parasite-free populations. Therefore, our results suggest that the tapeworm infection confers some advantage to T. castaneum and are in contrast to the expectation based on mathematical studies and verbal arguments. Disagreements between experimental results and the hypothesized predictions probably reflect the effect of parasite-induced changes in intraguild predation. Our results suggest that theories on parasite effects of competition need to consider the complex nature of host-parasite associations, including the effect of parasites on host behaviors.