Journal of Applied Ecology 2006 43 , 848���857 �� 2006 The Authors. Journal compilation �� 2006 British Ecological Society Blackwell Publishing Ltd REVIEW Management of plant invasions mediated by frugivore interactions YVONNE M. BUCKLEY 1,2 , SANDRA ANDERSON 3 , CARLA P. CATTERALL 4 , RICHARD T. CORLETT 5 , THOMAS ENGEL 6 , CARL R. GOSPER 7 , RAN NATHAN 8 , DAVID M. RICHARDSON 9 , MELISSA SETTER 10 , ORR SPIEGEL 8 , GABRIELLE VIVIAN-SMITH 7 , FRIEDERIKE A. VOIGT 11 , JACQUELINE E. S. WEIR 5 and DAVID A. WESTCOTT 12 1 The Ecology Centre, University of Queensland, School of Integrative Biology, St Lucia, Queensland 4072, Australia 2 CSIRO Sustainable Ecosystems, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Queensland 4067, Australia 3 School of Geography and Environmental Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand 4 Environmental Sciences, Griffith University, Nathan, Queensland 4111, Australia 5 Department of Ecology and Biodiversity, University of Hong Kong, Pokfulam Road, Hong Kong, China 6 Biogeography, University of Bayreuth, 95440 Bayreuth, Germany 7 CRC for Australian Weed Management, Alan Fletcher Research Station, Queensland Department of Natural Resources and Mines, PO Box 36, Sherwood, Queensland 4075, Australia 8 Movement Ecology Laboratory, Department of Evolution, Systematics and Ecology, The Hebrew University of Jerusalem, Givat Ram, 91904 Jerusalem, Israel 9 Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa 10 Queensland Department of Natural Resources and Mines, Centre for Wet Tropics Agriculture, PO Box 20, South Johnstone, Queensland 4859, Australia 11 School of Biological and Conservation Science, University Natal, Private Bag X01, Scottsville, Pietermaritzburg, 3209 South Africa and 12 CSIRO Sustainable Ecosystems, the Rainforest CRC and the CRC for Australian Weed Management, Atherton, Queensland 4883, Australia Summary 1. Some of the most damaging invasive plants are dispersed by frugivores and this is an area of emerging importance in weed management. It highlights the need for practical information on how frugivores affect weed population dynamics and spread, how frugivore populations are affected by weeds and what management recommendations are available. 2. Fruit traits influence frugivore choice. Fruit size, the presence of an inedible peel, defensive chemistry, crop size and phenology may all be useful traits for consideration in screening and eradication programmes. By considering the effect of these traits on the probability, quality and quantity of seed dispersal, it may be possible to rank invasive species by their desirability to frugivores. Fruit traits can also be manipulated with biocontrol agents. 3. Functional groups of frugivores can be assembled according to broad species group- ings, and further refined according to size, gape size, pre- and post-ingestion processing techniques and movement patterns, to predict dispersal and establishment patterns for plant introductions. 4. Landscape fragmentation can increase frugivore dispersal of invasives, as many invasive plants and dispersers readily use disturbed matrix environments and fragment edges. Dispersal to particular landscape features, such as perches and edges, can be manipulated to function as seed sinks if control measures are concentrated in these areas. 5. Where invasive plants comprise part of the diet of native frugivores, there may be a conservation conflict between control of the invasive and maintaining populations of Correspondence: Yvonne M. Buckley, The Ecology Centre, University of Queensland, School of Integrative Biology, St Lucia, Queensland 4072, Australia (e-mail y.buckley@uq.edu.au).

849 Plant invasions and frugivore interactions �� 2006 The Authors. Journal compilation �� 2006 British Ecological Society, Journal of Applied Ecology , 43 , 848���857 the native frugivore, especially where other threats such as habitat destruction have reduced populations of native fruit species. 6. Synthesis and applications . Development of functional groups of frugivore-dispersed invasive plants and dispersers will enable us to develop predictions for novel dispersal interactions at both population and community scales. Increasingly sophisticated mechanistic seed dispersal models combined with spatially explicit simulations show much promise for providing weed managers with the information they need to develop strategies for surveying, eradicating and managing plant invasions. Possible con- servation conflicts mean that understanding the nature of the invasive plant���frugivore interaction is essential for determining appropriate management. Key-words: fruit traits, frugivore traits, functional groups, landscape fragmentation, conservation conflict, dispersal Journal of Applied Ecology (2006) 43 , 848���857 doi: 10.1111/j.1365-2664.2006.01210.x Introduction The proportion of invasive species that are animal dispersed is unknown estimates range from 8% of the naturalized flora of Victoria, Australia (Carr 1993) to 40% of ���representative invasive species��� (Cronk & Fuller 1995). Of the 20 species of weeds of national significance in Australia, five are fleshy fruited with known vertebrate dispersers (Brunner, Harris & Amor 1976 Liddy 1985 Stansbury 2001 Setter et al . 2002 Gosper 2004), one is ant dispersed (Richardson & Hill 1998) and three receive some dispersal by livestock (Lonsdale, Miller & Forno 1989 Brown & Carter 1998 Kriticos et al . 1999 van Klinken & Campbell 2001). Frugivore-mediated dispersal of invasive plants is therefore an area of emerging importance in the weed management sector, highlighting a need for informa- tion on how frugivores affect weed population dynamics and spread, how frugivore populations are affected by weeds, and what management recommendations are available. Research on frugivory and weed man- agement could benefit from a closer synthesis of the two fields. The kind of dispersal vector is a determinant of the resulting seed shadow (the distribution of seeds in space around the parent), with animal-dispersed species having longer mean dispersal distances than wind- dispersed species (Clark et al . 2005). Furthermore, invasions where dispersal is mediated by frugivores have distinctive ecological features. (i) Dispersal depends on the presence of suitable frugivores, thus the variation in frugivore assemblages between regions and habitats potentially places a variable filter on the success of invasive plant species. (ii) Mutualism imparts a recip- rocal positive effect on each partner���s rate of popu- lation increase. (iii) Plant or frugivore species may be simultaneously involved in interactions with multiple species. There will therefore be both community- and population-level consequences of the invasive plant��� frugivore interaction. Two recent reviews of invasive plant���frugivore inter- actions (Richardson et al . 2000 Gosper, Stansbury & Vivian-Smith 2005) have covered the extent and func- tions of this mutualism among invasive plant species. We discuss how a deeper understanding of the function of the invasive plant���frugivore interaction can influence management of invasive plant populations. While it has proved difficult to find traits that correlate with invasiveness generally across taxa and widely different functional groups (Kolar & Lodge 2001), we argue that the assessment of how plant and disperser traits influ- ence dispersal and demographic processes can be used to rank risks of invasion, guide surveillance and detection, assess indirect positive or negative effects and manage invasions. We focus on six areas of research from functional group traits to landscape-scale and community processes that we believe can be integrated and used to improve management of plant invasions: fruit traits, frugivore traits, plant establishment, land- scape structure, models of spread and community interactions. Fruit traits The success of invasive plant species is partly attributed to fruit traits that favour effective seed dispersal (Panetta & McKee 1997 Baret, Le Bourgeois & Strasberg 2005). One valuable but surprisingly rarely applied approach to assessing the role of fruit traits in promoting invasion is to compare the fruit traits and dispersal performance of co-occurring native and invasive plants (Daehler 2003). Two studies have shown that invasive species in their exotic range are superior to native congeners in terms of traits influencing fruit removal and in both cases the invasives had higher removal rates (Sallabanks 1993 Vila & D���Antonio 1998). In contrast, three other com- parisons showed no clear differences (Montaldo 2000 Greenberg, Smith & Levey 2001 Drummond 2005). With so few studies it is difficult to generalize how- ever, evidence from the frugivory literature indicates