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dc.contributor.authorMilton, S.J.
dc.contributor.authorWilson, J.R.U.
dc.contributor.authorRichardson, D.M.
dc.contributor.authorSeymour, C.L.
dc.contributor.authorDean, W.R.J.
dc.contributor.authorIponga, D.M.
dc.contributor.authorProcheş, Ş.
dc.date.accessioned2007-06-19T10:58:09Z
dc.date.available2007-06-19T10:58:09Z
dc.date.issued2007
dc.identifier.issn0022-0477
dc.identifier.urihttp://hdl.handle.net/123456789/293
dc.description.abstract1 The cultivation and dissemination of alien ornamental plants increases their potential to invade. More specifically, species with bird-dispersed seeds can potentially infiltrate natural nucleation processes in savannas. 2 To test (i) whether invasion depends on facilitation by host trees, (ii) whether propagule pressure determines invasion probability, and (iii) whether alien host plants are better facilitators of alien fleshy-fruited species than indigenous species, we mapped the distribution of alien fleshy-fruited species planted inside a military base, and compared this with the distribution of alien and native fleshy-fruited species established in the surrounding natural vegetation. 3 Abundance and diversity of fleshy-fruited plant species was much greater beneath tree canopies than in open grassland and, although some native fleshy-fruited plants were found both beneath host trees and in the open, alien fleshy-fruited plants were found only beneath trees. 4 Abundance of fleshy-fruited alien species in the natural savanna was positively correlated with the number of individuals of those species planted in the grounds of the military base, while the species richness of alien fleshy-fruited taxa decreased with distance from the military base, supporting the notion that propagule pressure is a fundamental driver of invasions. 5 There were more fleshy-fruited species beneath native Acacia tortilis than beneath alien Prosopis sp. trees of the equivalent size. Although there were significant differences in native plant assemblages beneath these hosts, the proportion of alien to native fleshyfruited species did not differ with host. 6 Synthesis. Birds facilitate invasion of a semi-arid African savanna by alien fleshyfruited plants, and this process does not require disturbance. Instead, propagule pressure and a few simple biological observations define the probability that a plant will invade, with alien species planted in gardens being a major source of propagules. Some invading species have the potential to transform this savanna by overtopping native trees, leading to ecosystem-level impacts. Likewise, the invasion of the open savanna by alien host trees (such as Prosopis sp.) may change the diversity, abundance and species composition of the fleshy-fruited understorey. These results illustrate the complex interplay between propagule pressure, facilitation, and a range of other factors in biological invasions.en
dc.description.sponsorshippostdoctoral funding from Stellenbosch University. German Ministerium für Bildung und Wissenschaft (BMBF) under project number 01C0024 (BIOTA – southern Africa) and the Gordon Sprigg Scholarship. DST-NRF Centre of Excellence at the Percy FitzPatrick Institute of African Ornithology for use of the Benfontein Research Centre as our base. The Commanding Officer Maj. J.A. Myburgh of the Kimberley Military Base is thanked for allowing access to the base and surrounds.en
dc.format.extent428550 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoenen
dc.publisherBlackwellen
dc.subjectbiological invasionsen
dc.subjectclumpingen
dc.subjectfrugivorous birdsen
dc.subjectimpactsen
dc.subjectinvasive speciesen
dc.subjectmutualismsen
dc.subjectornithochoryen
dc.subjectpropagule pressureen
dc.subjectseed dispersalen
dc.subjectSouth Africaen
dc.subjectspatial analysisen
dc.subjectvegetation changeen
dc.titleInvasive alien plants infiltrate bird-mediated shrub nucleation processes in arid savannaen
dc.typeJournal Articlesen
dc.cibjournalJournal of Ecologyen
dc.cibprojectInteractions between indigenous and invasive speciesen


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