Taxonomic and ecological studies of the Tasmanian Eucalyptus-defoliating paropsids (coleoptera: chrysomelidae), with particular reference to Chrysophtharta bimaculata (Olivier)

摘要

This study investigates the taxonomy and ecological relationshipsudof the Tasmanian Eucalyptus-defoliating paropsid beetles of the familyudChrysomelidae. In particular, the host-plant relationships, lifeudhistory and population ecology of Chrysophtharta bimaculata (Olivier)uda major forest pest in Tasmania, are investigated.udA survey of eucalypt forest and woodland over much of theudisland revealed the presence of at least thirty-six paropsid speciesudwhich fed on the foliage of eucalypts. These species belonged toudfive genera, viz: Paropsis Olivier (sensu stricto) (nine species),udTrachymela Weise (eight species), Chrysophtharta Weise (thirteenudspecies), Paropsisterna Motschulsky (three species) and SterromelaudWeise (three, or possibly four species).udAll species were described and indicated by a code, but it wasudonly possible to positively identify twenty-three species. Noudattempt was made to name new species, since it was considered thatudin the absence of a recent revision of the entire paropsid fauna,udthis would only serve to increase nomenclatural confusion withinudthe group. Keys to adults and fourth instar larvae are provided.udRecords of Eucalyptus species on which each species of Paropsis wasudfound at each collecting locality are given. The Tasmanian island paropsid fauna on eucalypts is compared and contrasted to that ofudmainland Australia in the light of current limited knowledge.udEcological relationships of the more common paropsids areuddiscussed in relation to r and K strategy and niche differentiation.udThe host-plant relationships of two very common, highly r-selectedudspecies, Chrysophtharta bimaculata and C. agricola (Chapuis) wereudstudied in detail in the field, insectary and laboratory. udC. bimaculata showed a field preference for Monocalyptus species ofudthe series Obliquae, while C. agricola preferred Symphyomyrtusudspecies. In laboratory larval feeding trials, C. bimaculataudperformed better on a Monocalyptus species (E. delegatensis) thanudon a Symphyomyrtus species (E. dalrympleana) while C. agricolaudperformed equally well on both species. C. bimacutata developedudfaster but was a less efficient feeder than C. agricola onudE. delgatensis. It was therefore inferred that C. bimaculataudwas more highly r-selected than C. agricola, competitivelyuddisplacing the latter species from E. delegatensis.udDetailed studies were made of the life history andudpopulation ecology of C. bimaculata. This species was shown to beudunivoltine at least in N.W. Tasmania,and not bivoltine as previouslyudconsidered. Partial population budgets were prepared for threeudpopulations. A major mortality factor in populations of immatureudC. bimaculata was the predatory coccinellid, Cleobora mellyiudMulsant which accounted for up to 74 percent of egg mortality.udEgg parasitization and larval parasitization by the braconidudspecies Eadya paropsidis were described for the first time.udThe pest potential of C. bimaculata is discussed in the light ofudits host-plant relationships, ecological strategies of itsudpreferred hosts, and other population determinants.