Distribution and bait preference of the Argentine ant in natural vegetation
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Since its introduction in 1898 into South Africa, the Argentine ant, Linepithema humile, has invaded human-occupied areas (i.e. urban and agricultural areas) and natural areas characterised by few, if any, anthropogenic disturbances. However, compared to other countries in which the Argentine ant has been recorded, and until the past few decades, very little research had been done on this invasive ant in South Africa. Consequently, several issues concerning its ecological and social effects are still under-researched. The first of these issues concerns 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 are occupied by this invasive ant, a study was conducted in the Western Cape Province (WCP). It was found that, of the 614 PAs documented for WCP, ten have a known presence and nine known absence records of the Argentine ant. The remainder of the PAs have no known occupancy records for this ant. A second issue concerns the seasonal bait preference of the Argentine ant in a fynbos habitat. Six bait treatments (two carbohydrate and protein baits, a mixture of the carbohydrate and protein treatments, and a control) were applied in Jonkershoek Nature Reserve (JNR)across a sampling grid in four different Latin Square designs, i.e. once for every season. Based on these experiments, it was determined that the Argentine ant prefers the mixture of carbohydrate and protein treatments, and that this preference does not change according to season. Furthermore, previous studies conducted in JNR (in WCP) determined the existence of a distribution boundary of Argentine ants in an area known as Swartboschkloof. Therefore, the third issue concerned the exact location of the distribution boundary and possible reasons for its establishment. This distribution boundary of the Argentine ant was found to be present 450 m from Swartboschkloof hiking trail. A combination of several explanatory variables may contribute to the maintenance of this boundary, i.e. a change in the horizontal and vertical vegetation distribution, as well as in the slope and aspect across the distribution boundary. With these explanatory variables, the increasing presence of an indigenous ant species, Anoplolepis custodiens, from this boundary may also have contributed to the distribution boundary. The final issue concerns the public perceptions of invasive alien species (IAS) in general and the Argentine ant specifically, at JNR. This study revealed that the majority of visitors to JNR were aware of the presence of IAS in South Africa and in 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 role in conservation.