Keywords: Invasive species Ecosystem function Insect pests Invasive plants Ecological restoration Biological control Natural ecosystems a b s t r a c tOf the 70 cases of classical biological control for the protection of nature found in our review, there were fewer projects against insect targets (21) than against invasive plants (49), in part, because many insect biological control projects were carried out against agricultural pests, while nearly all projects against plants targeted invasive plants in natural ecosystems. Of 21 insect projects, 81% (17) provided benefits to protection of biodiversity, while 48% (10) protected products harvested from natural systems, and 5% (1) preserved ecosystem services, with many projects contributing to more than one goal. In contrast, of the 49 projects against invasive plants, 98% (48) provided benefits to protection of biodiversity, while 47% (23) protected products, and 25% (12) preserved ecosystem services, again with many projects contributing to several goals. We classified projects into complete control (pest generally no longer important), partial control (control in some areas but not others), and ''in progress," for projects in development for which outcomes do not yet exist. For insects, of the 21 projects discussed, 62% (13) achieved complete control of the target pest, 19% (4) provided partial control, and 43% (9) are still in progress. By comparison, of the 49 invasive plant projects considered, 27% (13) achieved complete control, while 33% (16) provided partial control, and 49% (24) are still in progress. For both categories of pests, some projects' success ratings were scored twice when results varied by region. We found approximately twice as many projects directed against invasive plants than insects and that protection of biodiversity was the most frequent benefit of both insect and plant projects. Ecosystem service protection was provided in the fewest cases by either insect or plant biological control agents, but was more likely to be provided by projects directed against invasive plants, likely because of the strong effects plants exert on landscapes. Rates of complete success appeared to be higher for insect than plant targets (62% vs 27%), perhaps because most often herbivores gradually weaken, rather than outright kill, their hosts, which is not the case for natural enemies directed against pest insects. For both insect and plant biological control, nearly half of all projects reviewed were listed as currently in progress, suggesting that the use of biological control for the protection of wildlands is currently very active.

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Effective study in the native range to identify potential agents underpins all efforts in classical biological control of weeds. Good agents that demonstrate both a high degree of host specificity and the potential to be damaging are a very limited resource and must therefore be carefully studied and considered. The overseas component is often operationally difficult and expensive but can contribute considerably more than a list of herbivores attacking a particular target. While the principles underlying this foreign component have been understood for some time, recently developed technologies and methods can make very significant contributions to foreign studies. Molecular and genetic characterisations of both target weed and agent organism can be increasingly employed to more accurately define the identity and phylogeny of them. Climate matching and modelling software is now available and can be utilised to better select agents for particular regions of concern. Relational databases can store collection information for analysis and future enquiry while quantification of sampling effort, employment of statistical survey methods and analysis by techniques such as rarefaction curves contribute to efficient and effective searching. Obtaining good and timely identifications for discovered agent organisms is perhaps the most serious issue confronting the modern explorer. The diminishing numbers of specialist taxonomists employed at the major museums while international and national protocols demand higher standards of identity exacerbates the issue. Genetic barcoding may provide a very useful tool to overcome this problem. Native-range work also offers under-exploited opportunities for contributing towards predicting safety, abundance and efficacy of potential agents in their target environment.

Aims A molecular genetic distance study has been used in an initial survey to identify subspecies and genotypes of the weed Acacia nilotica in Australia, information needed to find suitable biocontrol agents. We use patterns of DNA sequence variation (in two DNA fragments) from each of the nine described subspecies of Acacia nilotica (L.) Delile (Leguminosae: Mimosoideae) that is to determine their genetic similarity, to verify if the Australian populations are A. nilotica ssp. indica (Benth.) Brenan, and to establish if any other subspecies are present in Australia.Location Australia and southern Africa through the Arabian peninsular to the Indo-Pakistan subcontinent.Methods Representative specimens from the global distribution of the nine A. nilotica subspecies were sourced primarily from herbaria sheet specimens where available, and secondarily from field collections. These specimens together with related outgroups from Mimosoideae were genetically analysed using the DNA fragments trnL and internal transcribed spacer one (ITS1). We calculated a similarity index as set out in paup* using upgma (Unweighted Pair-Group Method Arithmetic average) methods to cluster taxa to produce a genetic distance phenogram.Results Sequence results from ITS1 and trnL DNA fragments identified seven of the described subspecies of A. nilotica. Acacia nilotica ssp. cupressiformis (J. Stewart) Ali & Faruqi and A. nilotica ssp. adstringens (Schumach. & Thonn.) Roberty were not found to be genotypically distinct from A. nilotica ssp. indica and A. nilotica ssp. nilotica, respectively, based on the two DNA fragments. Subspecific ITS1 genotypes were geographically distributed similarly to previous reports that were based on morphology, with the exception that the hemispherica ITS1 genotype also occurred in Somalia. We confirmed that the Australian A. nilotica populations are mostly comprised of subspecies indica, but in addition, some individuals were found to be genetically identical to an unidentified Pakistan genotype not previously reported as occurring in Australia.Main conclusions Australian A. nilotica populations originated from India and Pakistan and we recommend further analysis to determine the complete genetic diversity profile and origins of the Australian populations. We highlight the importance of determining any hybridization between Australian populations of A. nilotica and native subgenus Acacia species. This study demonstrates the importance of genotyping weed species targeted for biocontrol and/or listed host specificity test species that may be easily misidentified.