Distribution and bait preference of the Argentine ant in natural vegetation

[摘要] ENGLISH ABSTRACT: Since its introduction in 1898 into South Africa, the Argentine ant, Linepithema humile [Mayr 1868(Hymenoptera: Formicidae)], has invaded human-occupied areas (i.e. urban and agricultural areas)and natural areas characterised by few, if any, anthropogenic disturbances. However, compared toother countries in which the Argentine ant has been recorded, and until the past few decades, verylittle research had been done on this invasive ant in South Africa. Consequently, several issuesconcerning its ecological and social effects are still under-researched. The first of these issuesconcerns the lack of knowledge about the distribution of the Argentine ant in the natural areas,particularly the protected areas (PAs), of South Africa. In order to determine how many PAs areoccupied by this invasive ant, a study was conducted in the Western Cape Province (WCP). It wasfound that, of the 614 PAs documented for WCP, ten have a known presence and nine knownabsence records of the Argentine ant. The remainder of the PAs have no known occupancy recordsfor this ant. A second issue concerns the seasonal bait preference of the Argentine ant in a fynboshabitat. Six bait treatments (two carbohydrate and protein baits, a mixture of the carbohydrate andprotein treatments, and a control) were applied in a fynbos habitat across a sampling grid in fourdifferent Latin Square designs, i.e. once for every season. Based on these experiments, it wasdetermined that the Argentine ant prefers the mixture of carbohydrate and protein treatments, andthat this preference does not change according to season. Furthermore, previous studies conductedin Jonkershoek Nature Reserve [JNR (in WCP)] determined the existence of a distribution boundaryof Argentine ants in an area known as Swartboschkloof. Therefore, the third issue concerned theexact location of the distribution boundary and possible reasons for its establishment. Thisdistribution boundary of the Argentine ant was found to be present 450 m from Swartboschkloofhiking trail. A combination of several explanatory variables may contribute to the maintenance ofthis boundary, i.e. a change in the horizontal and vertical vegetation distribution, as well as in theslope and aspect across the distribution boundary. With these explanatory variables, the increasingpresence of an indigenous ant species, Anoplolepis custodiens, from this boundary may also havecontributed to the distribution boundary. In addition, the short-term effect of a fire that sweptthrough this area was also assessed, which revealed that Argentine ants are severely negativelyaffected by fire (at least over the short-term), i.e. their abundance decreased considerably after thefire and their local distribution range contracted. The final issue concerns the public perceptions ofinvasive alien species (IAS) in general and the Argentine ant specifically, at JNR. This studyrevealed that the majority of visitors to JNR were aware of the presence of IAS in South Africa andin its PAs, while very few visitors knew about the Argentine ant. This study also revealed that future research concerning South Africans perceptions of IAS might play a strong contributing rolein conservation.

[发布机构] Stellenbosch University