Reproductive compatibility and variation in survival and sex ratio between two geographic populations of Diadromus collaris, a pupal parasitoid of the diamondback moth, Plutella xylostella

Abstract

Diadromus collaris (Gravenhorst)(Hymenoptera: Ichneumonidae) has been recordedin many parts of the world as a major pupalendoparasitoid of the diamondback moth Plutella xylostella (Linnaeus) (Lepidoptera:Plutellidae). Experiments were conducted tocompare reproductive compatibility andperformance as affected by temperature betweentwo geographic populations of D.collaris, one from Hangzhou, Zhejiang and theother from Lishan, Taiwan, China. The numbersand sex ratio of progeny in all possiblecrosses and backcrosses were similar to thoseobtained within each of the populations,demonstrating complete reproductivecompatibility between the two populations. Thetwo populations showed similar responses totemperature with respect to development time,adult longevity and number of host pupaeparasitized per female. However, the populationfrom Hangzhou achieved higher rates of survivalfrom larva to adult emergence at hightemperatures and had higher proportions offemale progeny at some temperatures, than thepopulation from Lishan. The Hangzhou populationachieved higher intrinsic rates of increase atall temperatures tested from 15 to33.5 °C, and the differences weresignificant at 30 and 32 °C. Thedifferences between the two populations inability to survive high temperatures mayreflect their adaptation to local climates. Thesignificance of the intraspecific variationsrevealed is discussed with regard to the use ofgeographic populations of the parasitoid in thebiological control of P. xylostella.