Evolution of growth traits in invasive Pereskia aculeata (Cactaceae): testing the EICA hypothesis using its specialist herbivore, Catorhintha schaffneri (Coreidae).

BACKGROUND Species introduced into new habitats are fitter than their native populations as hypothesised by the 'Evolution of Increased Competitive Ability' (EICA). Here Pereskia aculeata Miller was used as a model to test EICA and explore how 'enemy release' may have influenced invasion success of its 400-year-old introduced populations (genotypes) compared to native ones. Plant growth traits (height and shoot length) of fifteen genotypes [four from the introduced range (South Africa), eleven from the native range (Brazil and Argentina, Venezuela and The Dominican Republic)] were assessed. Damage and impact of a shoot-feeding, sap-sucking specialist Catorhintha schaffneri Brailovsky & Garcia on ten genotypes were also compared. RESULTS All, but one, invasive genotypes were significantly taller than the native genotypes. Though the invasive genotypes were relatively more damaged by herbivory than some of the native genotypes, the observed differences were not completely explained by their origins. Nonetheless, the findings partially supported the predictions of the EICA hypothesis, because invasive genotypes were generally taller than native genotypes, but did not fully support the hypothesis because they were not always more damaged than the native genotypes by C. schaffneri. CONCLUSION The invasive genotypes had an advantage in the introduced range as they can climb neighbouring vegetation more quickly than the native ones, but the damage incurred by the invasive genotypes relative to the native genotypes only suggests that C. schaffneri would be as damaging in South Africa, where it serves as a biocontrol agent, as it is in the native distribution in Brazil. This article is protected by copyright. All rights reserved.