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dc.contributor.authorNghidinwa Kirsti, C.en
dc.date.accessioned2010-03-01T01:48:22Z
dc.date.issued2009en
dc.identifier.urihttps://hdl.handle.net/10182/1438
dc.description.abstractThere are many factors that have been proposed to contribute to plant invasiveness in nonnative ecosystems. Traits of invading species are one of them. It has been proposed that successful species at a certain invasion stage share particular traits, which could be used to predict the behaviour of potentially invasive plants at the respective stage. Three main stages of invasion are distinguished: introduction, naturalization, and invasion. I conducted a stageand trait-based analysis of available data for the invasion of New Zealand by the flora of southern Africa. Using 3076 southern African native vascular plant species introduced into New Zealand, generalised linear mixed model analysis was conducted to assess association of several species traits with the three invasion stages. The results showed that plant traits were significantly associated with introduction but fewer traits were associated with naturalization or invasion, suggesting that introduction can be predicted better using plant traits. It has been also hypothesized that species may become invasive in non-native ecosystems because they are removed from the regulatory effects of coevolved natural enemies (Enemy Release hypothesis). A detailed field study of the succulent plant Cotyledon orbiculata var. orbiculata L. (Crassulaceae) was conducted in the non-native New Zealand and native Namibian habitats to compare the extent of damage by herbivores and pathogens. C. orbiculata is a southern African species that is currently thriving in New Zealand in areas seemingly beyond the climatic conditions in its native range (occurring in higher rainfall areas in New Zealand than are represented in its native range). As hypothesised, C. orbiculata was less damaged by herbivores in New Zealand but, contrary to expectation, more infected by pathogens. Consequently, the plant was overall not any less damaged by natural enemies in the non-native habitat than in its native habitat, although the fitness impacts of the enemy damage in the native and invaded ranges were not assessed. The results suggest that climatic conditions may counteract enemy release, especially in situations where pathogens are more prevalent in areas of higher rainfall and humidity. To forecast plant invasions, it is concluded that species traits offer some potential, particularly at the early stage of invasion. Predicting which introduced plants will become weeds is more difficult. Enemy release may explain some invasions, but climatic factors may offset the predictability of release from natural enemies.en
dc.language.isoenen
dc.publisherLincoln Universityen
dc.subjectplant ecologyen
dc.subjectinvasive speciesen
dc.subjectinvasionen
dc.subjectinvasion stagesen
dc.subjectintroduced plantsen
dc.subjectnaturalizationen
dc.subjectspecies traitsen
dc.subjectherbivoryen
dc.subjectplant–herbivore interactionsen
dc.subjectplant pathogensen
dc.subjectsucculent plantsen
dc.subjectecologyen
dc.subjectsouthern Africaen
dc.subjectsouthern African floraen
dc.subjectNamibiaen
dc.subjectNew Zealanden
dc.subjectrainfallen
dc.titleWhy are some species invasive? : determining the importance of species traits across three invasion stages and enemy release of southern African native plants in New Zealanden
dc.typeThesis
thesis.degree.grantorLincoln Universityen
thesis.degree.levelMastersen
thesis.degree.nameMaster of Scienceen
dc.subject.marsdenFields of Research::270000 Biological Sciences::270700 Ecology and Evolutionen
dc.subject.marsdenFields of Research::270000 Biological Sciences::270400 Botanyen
lu.contributor.unitLincoln Universityen
lu.contributor.unitBio-Protection and Ecologyen
pubs.organisational-group/LU
pubs.organisational-group/LU/BPEC
pubs.publication-statusPublisheden


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