Host–parasite genome relationships in Acridid grasshoppers. I. Variation in the isoenzymes of the Caledia captiva species complex and in the gut bacterium Enterobacter cloacae

Abstract

Isoenzymic variation was investigated in populations of the four recognized taxa of the Australian acridine Caledia captiva and in 110 isolates of the bacterium Enterobacter cloacae present in their guts. Four types of colony morphology, of which two were common, were discernible in these bacteria. All representatives of each type appeared to be very close to typical members of E. cloacae. The genetic diversity of the eight bacterial enzymes scored was very high, both overall and in respect of the two common morphological types. This diversity is consistent with selective neutrality and is too great to be explained by selective discrimination between genotypes. There was no compelling evidence for any interaction between the host and bacterial genotypes. The results thus argue against the possibility that the parasites are involved in a system of frequency dependent selection. There was also no evidence of an association of bacterial type with divergence between the taxa of the C. captiva complex. Key words: host–parasite, isoenzymes, grasshoppers, bacteria.