Asymmetric Competition in a Natural Population of Antlion Larvae

• Published in: Oikos 1993-12, Vol.68 (3), p.525-530
• Main Authors: Paulo Inácio K. L. Prado, Bedê, Lúcio Cadaval, de Faria, Maurício Lopes
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Caves; Demecology; Ecological competition; Food deprivation; Frequency distribution; Fundamental and applied biological sciences. Psychology; Insect larvae; Intraspecific competition; Invertebrates; Larvae; Logistics; Microhabitats; Population density; Protozoa. Invertebrata
• ISSN: 0030-1299; 1600-0706
• DOI: 10.2307/3544921

We investigated the existence and kind of intraspecific competition among larvae of Myrmemeleon uniformis (Neuroptera: Myrmeleontidae), a pit-trapping antlion, in southeast Brazil. The population occupied an area of about 120 m2 in a shallow cave, where we demarcated a 1 × 1 m permanent plot. Larval pits were mapped once a week for two months, and the time each individual remained in the same location was estimated. Disapperance represents death or movement in search of a better site. Pit diameter was significantly correlated with larva size. Weekly residence probability increases with pit diameter and decreases with the relative size of the nearest neighbor (neighbor pit radius/neighbor distance). A logistic model also indicates that these competitive asymmetries are smaller for the part of the plot closer to the cave entrance, suggesting that microhabitat influences the magnitude of differences among competitive abilities. Pit size frequency distributions were positively skewed during the whole study period. Low transition probabilities to larger pit diameter classes and a high proportion of pits which diminish in size weekly suggest that food is limiting. The population declined over the study period, and increased in spatial regularity, further evidence of intraspecific competition.