1032 Management history determines gene flow in a prominent invader Waafeka Vardien, David M. Richardson, Llewellyn C. Foxcroft, John R. U. Wilson and Johannes J. Le Roux W. Vardien, D. M. Richardson, L. C. Foxcroft, J. R. U. Wilson and J. J. Le Roux (jacoleroux01@gmail.com), Centre for Invasion Biology, Dept of Botany and Zoology, Stellenbosch Univ., Matieland 7602, South Africa. LCF also at: Conservation Services, South African National Parks, Skukuza 1350, South Africa. JRUW also at: South African National Biodiversity Inst., Kirstenbosch National Botanical Gardens, Claremont 7735, South Africa. Invasive plants pose substantial threats to protected areas globally. Although management can limit impacts, spread and reinvasion from neighbouring areas into protected areas are a major and an on-going problem for land managers. However, identifying the main sources of propagules and the dimensions of invasion pathways is challenging. Tis study used popu- lation genetic markers [inter simple sequence repeats (ISSRs) and amplified fragment length polymorphisms (AFLPs)] to infer the source(s) of re-colonization and dispersal patterns for a typical invader of riparian and terrestrial habitats ( Lantana camara) along the Sabie-Sand catchment, one of the most important river systems flowing into and across South Africa’s flagship protected area, the Kruger National Park (KNP). Results indicate that populations located along the lower reaches of the Sabie and Sand tributaries harboured substantially higher genetic diversity than those in the upper Sabie catchment. Bayesian assignments indicated that the upper Sabie tributary contributed far fewer propagules than the Sand tributary to the lower Sabie River. Current invasion patterns are due to a combination of a major flood event in 2000 and differences in the degree to which the upstream reaches were managed after the flooding. Te major flood of 2000 effectively cleared lantana from the riparian areas. However, whereas on-going management efforts against riparian species in the KNP have been effective, rendering the upper Sabie relatively clear of lantana, only a small part of the Sand tributary falls under juris- diction of the KNP and has received consistent management attention. Te reinvasion of the lower Sabie in the KNP was therefore almost entirely by propagules from the Sand tributary. Te study highlights the important role that molecular tools can play in determining dispersal dynamics and directing invasive species management. For invasive plant species that invade both riparian habitats and landscapes away from rivers in protected areas, such as lantana, management must focus on all major sources of propagules to limit reinvasion. Some invasive alien species cause substantial ecological damage and pose major threats to biodiversity (Gurevitch and Padilla 2004), to the extent that biological invasions are an important driver of global environmental change (Butchart et al. 2010). Protected areas form one of the most important opportunities for conserving biodiversity and ecosystem services globally (Gaston et al. 2008), and invasive species directly threaten the ability of these areas to meet their mandate. Invasive species affect ecosystem ser- vices (Vilà et al. 2010), disrupt fire regimes (D’Antonio and Vitousek 1992, Rossiter-Rachor et al. 2009) and nutrient cycling (Ehrenfeld 2003), and have direct impacts on native species (Vonshak et al. 2010). As key focus areas for conser- vation, protected areas can, and should, be at the forefront of systematic management of invasive species. However, limited resources often result in insufficient attention being given to objective prioritization and the integration of all available information to ensure effective management. Eradication is feasible for some species, but for most widespread species complete removal is untenable (Rejmánek and Pitcairn 2002). For widespread invaders, efficient man- agement requires a thorough understanding of the many factors that contribute to persistence, proliferation and spread, such as life-history traits, seed bank dynamics, dis- persal vectors and the role of propagule pressure (Lockwood et al. 2007). Different mechanisms affect invasions at differ- ent stages and these interact in complex ways with features of the receiving environment. For example, dispersal vectors (birds, roads, rivers, humans and animals) are particularly important as they can exacerbate the spread of invasive species from outside sources into protected areas (Naiman and Décamps 1997, Pauchard and Alaback 2004, Dovrat et al. 2012). Most protected areas are embedded in a landscape of unprotected land and can be considered ‘islands ’ in a sea of different land uses, onto which urban development is rapidly encroaching (McDonald et al. 2008). Although alien species are sometimes introduced directly into protected areas, the surrounding unprotected areas often represent a significant potential source and multiple pathways of Ecography 36: 1032–1041, 2013 doi: 10.1111/j.1600-0587.2012.00120.x © 2013 Te Authors. Ecography © 2013 Nordic Society Oikos Subject Editor: Francisco Pugnaire. Accepted 21 December 2012