An empirical model of the sympatric coexistence of two strains of the endoparasitoid wasp Venturia canescens.
Recent research has demonstrated that a laboratory culture of the asexual solitary endoparasitoid wasp Venturia canescens Grav. (Hymenoptera: Ichneumonidae) contains two genetically and phenotypically distinct lines, coexisting on their host the flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The basis to the coexistence of the two lines appears to be differences in their reproductive success under single parasitism and superparasitism. Furthermore, examination of field-derived wasps from several locations has shown that the phenotypes displayed by the laboratory colonies also co-occur in field populations. Historically, the impossibility of showing that two species do not occupy separate niches has precluded any demonstration of sympatric coexistence in the field. Here we present the results of an iterative model that uses a range of experimental life history data to predict the stable composition of a mixed population of two lines displaying the laboratory phenotypes under different rates of superparasitism. The model predicts that sympatric coexistence of the two lines is possible when the overall rate of superparasitism is between 4 and 12% or greater. These values are within the rates reported for other solitary endoparasitoid wasp species in the field, and so demonstrate that the sympatric coexistence under natural conditions of two species that display the phenotypes observed in the laboratory lines is, in principle, possible.
Insect Molecular Biology Laboratory, Department of Plant and Pest Science, The University of Adelaide, Glen Osmond, Australia. harry.roberts@adelaide.edu.au
Harry L S
HL
Roberts
Michael
M
Keller
Otto
O
Schmidt
D000818:Animals; D005260:Female; D008954:Models, Biological; D010641:Phenotype; D014863:Wasps / Q000235:genetics / Q000502:physiology*