Molecular Systematics and Ecology of Invasive Kangaroo Paws in South Africa: Management Implications for a Horticulturally Important Genus
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Biol Invasions (2010) 12:3989–4002 DOI 10.1007/s10530-010-9818-4 ORIGINAL PAPER Molecular systematics and ecology of invasive Kangaroo Paws in South Africa: management implications for a horticulturally important genus J. J. Le Roux • S. Geerts • P. Ivey • S. Krauss • D. M. Richardson • J. Suda • J. R. U. Wilson Received: 27 November 2009 / Accepted: 31 March 2010 / Published online: 2 July 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Most legislation pertaining to non-native without bird pollination. Given the known propensity organisms is implicitly focussed at the individual of Kangaroo Paws to hybridise in their native range species level. However, in some cases interspecific in Australia, and confusion about the species identity hybrids can be more invasive than any of the parent of naturalized populations in South Africa, it was species. This is problematic for policy makers, and essential to resolve some key taxonomic issues in the for horticulturists developing or trading in new group. We constructed the first molecular phylogeny ornamental cultivars. We explore these issues in the for all species of the Kangaroo Paw group (genera context of the need to manage naturalized popula- Anigozanthos and Macropidia; family Haemodora- tions of Kangaroo Paws (Anigozanthos species) in ceae). As previously determined by taxonomists South Africa. Self-sustaining, dense populations of working on herbarium specimens, naturalized popu- naturalized Kangaroo Paws occur at several localities lations were identified as A. flavidus. In addition, we and are highly attractive to local nectar-feeding birds. also identified a second species, A. rufus. Relative The populations show high levels of seed set with or genome size estimates for Anigozanthos species J. J. Le Roux (&) Á D. M. Richardson Á J. R. U. Wilson S. Krauss Centre for Invasion Biology, Department of Botany School of Plant Biology, University of Western Australia, and Zoology, Stellenbosch University, Private Bag X1, Stirling Highway, Crawley, WA 6009, Australia Matieland, Stellenbosch 7602, South Africa e-mail: [email protected] J. Suda Department of Botany, Faculty of Science, Charles S. Geerts University in Prague, Prague, Czech Republic Department of Botany and Zoology, Stellenbosch University, Matieland, Stellenbosch 7602, South Africa J. Suda Institute of Botany, Academy of Sciences of the Czech P. Ivey Á J. R. U. Wilson Republic, Prague, Czech Republic Early Detection and Rapid Response Programme for Invasive Alien Plants, Kirstenbosch National Botanical Gardens, South African National Biodiversity Institute, Claremont 7735, South Africa S. Krauss Botanic Gardens and Parks Authority, Kings Park and Botanic Garden, Fraser Avenue, West Perth 6005, Australia 123 3990 J. J. Le Roux et al. indicated that small inter-specific differences in There have been several attempts to define which genome sizes are positively correlated to hybrid parameters and traits are pertinent to invasion risk for fitness. Anigozanthos flavidus and A. rufus have plants. For example, Richardson et al. (2000) sug- relatively ‘compatible’ genomes and may produce gested that spread of alien plants may be limited by a fertile hybrids under field conditions. However, for lack of suitable pollinators, and that pollinators in the species whose genome size differ more than *30%, introduced range may play an important role in there is little inter-specific compatibility and conse- maintaining reproductive fitness and in facilitating quently a very low risk of producing fertile hybrids. spread. Therefore, studies investigating the breeding In conclusion, we recommend that trade in Kangaroo system and/or pollination ecology of naturalized Paws in South Africa should be temporarily restricted plants can both aid risk assessment, and help estimate and that particular cultivars should first be subjected the potential for hybridisation (Ellstrand and Schierenbeck to a careful risk assessment. 2000). Such basic natural-history studies should run concurrently with management programs. This dual Keywords Biological invasions Á approach, whereby evidence is gathered without Kangaroo Paws Á Anigozanthos Á Macropidia Á compromising timely action to limit invasions, is Systematics Á Pollination Á Breeding system Á particularly important if there is a conflict of interest Self-compatibility Á Hybridisation or if co-operation needs to be encouraged or enforced to achieve eradication (Simberloff 2009). South Africa is developing new legislation to regulate the use, sale, and control of non-native Introduction species, as part of the National Environment Man- agement: Biodiversity Act (NEM:BA). NEM:BA Managing invasive populations by responding rap- follows on from the Conservation of Agricultural idly, even in the absence of insights from detailed Resources Act (CARA) in listing regulated species natural history studies, is cost-effective (Simberloff (Nel et al. 2004). Much of the legislation relies on 2003). This is because the cost and likelihood of species being defined entities, but the legislation also success of an eradication programme scales expo- attempts to deal with cultivars and hybrids. For nentially with the size of infestation (Rejma´nek and example: ‘‘all seed producing species or hybrids of Pitcairn 2002). However, any action taken, or Lantana that are non-indigenous to Africa’’ are planned, must be justifiable. This is particularly regulated. This specification, and prolonged engage- important when the invasive species has commercial ment with horticulturists, resulted in an agreement to or other value. Increasingly, the justification for destroy all stock of the lantana cultivar ‘Sundancer’ intervention needs to include objective verification when it was shown to produce fertile seeds, but to that the putative invader has a high risk of spreading continue trading with the species Lantana montevid- and/or causing damage. A key task in objective risk ensis, which does not produce fertile seeds in South analysis for biological invasions is the accurate Africa (although Czarnecki and Deng (2009) showed determination of the taxonomic identity of the subject some cultivars of L. montevidensis produce fertile and an assessment of its biogeographic status: native pollen and seed in experimental trials in the USA). versus alien (sensu Pysˇek et al. 2004). When the The regulations thus aim to be pro-active, but rely on taxonomic identity of an organism is clear and focussed research to provide key biological informa- the species is known to be invasive elsewhere in tion on which to base decisions. Continued support the world, initial risk assessment may require little from horticulturists will depend on the understanding additional information (Pheloung et al. 1999). How- that trade restrictions will only apply to taxa with a ever, if the taxonomy is uncertain (e.g., due to a lack high risk of invading, based on objective and of local expertise, cryptic invasions, or possible transparent criteria. hybridisation), elucidation of the taxonomic status is In this paper we describe a case-study in South crucial for legislation. Moreover, well-resolved tax- Africa of a group of Australian plants called Kangaroo onomy on its own is of little value if no additional Paws (the genera Anigozanthos and Macropidia). information is available. We assess the current extent of invasion of known 123 Molecular systematics and ecology 3991 naturalized populations, place this in a phylogenetic supporting its monotypic status (Hopper 1980; context, and, by exploring genome compatibility, Hopper and Campbell 1977; Hopper et al. 1999, assess the likelihood of hybridisation. Based on these 2009) while others have argued in favour of it being findings we provide recommendations on how to lumped within Anigozanthos (Anderberg and Eldena¨s accommodate this group of plants in developing 1991; Simpson 1990). Relationships between closely- regulations. related taxa within Anigozanthos are also unclear (Hopper 1980). Contributing to this taxonomic obscurity is the ease with which some species within Materials and methods Anigozanthos hybridise (Hopper 1977a, b, 1978, 1980; Hopper and Burbidge 1978; Shchori et al. Study system 1995). Kangaroo Paws are cultivated commercially in Kangaroo Paws are perennial herbs native to Western several countries around the world and at least 26 Australia from the genera Anigozanthos and Macro- cultivars are registered with the Australian Cultivar pidia (Haemodoraceae). Adaptations to bird pollina- Registration Authority (http://www.anbg.gov.au/acra/ tion, unusual flower morphology, and colouration acra-list-2009.html#a). In its native country, popula- (Fig. 1) make them popular and important horticul- tions of A. flavidus have naturalized and are spreading tural species in many parts of the world (Tsror et al. in New South Wales and South Australia (Australian 2005). Twelve species of Kangaroo Paws are cur- Native Plants Society 2009; Martin O’Leary, per- rently recognized (Hopper 1987); 11 in the genus sonal communication 2009) and are considered Anigozanthos and a single species in the genus serious environmental weeds (Hoskins et al. 2007). Macropidia (M. fuliginosa). The taxonomy of Hopper (1993) noted that A. flavidus is extremely Kangaroo Paws is problematic and has been the competitive and indeed the most invasive and robust subject of numerous studies (Anderberg and Eldena¨s species of Kangaroo Paw. Despite this, A. manglesii 1991; Hopper 1980; Hopper and Campbell 1977; is the only taxon listed in Randall’s