Exotic Arthropod Research Articles

Rove beetles (Coleoptera: Staphylinidae) in northern Nearctic forests

AbstractRove beetles are useful subjects for Nearctic forest biodiversity work because they are abundant, diverse, and easily collected, and have strong habitat affinities. Excellent identification keys exist for most groups, although there is a dearth of ecological and life-history information. There is considerable variation in species composition and abundance within the active summer season and in abundance from year to year. Community composition varies among larger geographical regions and to a lesser extent among forest types in more localized areas. Within the Nearctic boreal forest there are significant differences between beetle communities from the eastern and western portions. For the most part, the same species tend to dominate rove beetle communities in the western boreal forest. At the landscape level there are differences in rove beetle communities along successional gradients. In the boreal forest the communities of younger aspen-dominated and older conifer-dominated stands are somewhat distinct, with intermediate-aged stands containing a mix of the two communities. At the ecosite and microsite level there is significant variation, which remains poorly understood. Fire is the dominant mode of disturbance in the Nearctic boreal forest. It has a profound effect on rove beetles by destroying the forest communities and resetting the successional trajectory to the earliest stages. The burn pattern results in a patchwork of different communities at various stages in the successional cycle. In contrast to fire, forest harvesting does not directly destroy the rove beetle community, but to a large extent it destroys the forest habitat. This results in a unique rove beetle community characterized by a mix of forest species and open-ground specialists, and overall high diversity in this period of flux. In the years after harvesting, the rove beetle community goes through successional changes and becomes more similar to the forest community, but it skips the early postfire stage and proceeds along the successional trajectory more rapidly than after fire. In at least one forest type in western Canada, the post-fire and post-harvest communities, though similar, have not converged after 29 years. Other less direct effects of harvesting on rove beetles are a decrease in the proportion of the land base suitable for communities associated with older successional stages; alteration of forests by post-harvest site preparations and planting of exotic tree species; edge and fragmentation effects that are detrimental to the remaining forest surrounding harvested areas; and an influx of exotic arthropod species with affinities for disturbed sites. More information is needed on the habitat affinities of individual species. It is recommended that future work explore the effects of post-harvest forestry activities, fragmentation, and edges on rove beetles in forested habitats. As well, such studies should consider the effects on beetles of riparian zones and wetlands.

Population genetics of Scirtothrips perseae: tracing the origin of a recently introduced exotic pest of Californian avocado orchards, using mitochondrial and microsatellite DNA markers

AbstractThe Californian avocado industry has recently been impacted by the establishment of three exotic arthropod pests that are native to Mexico and Central America. Establishment of all three pests is thought to have resulted from illegal movement of host plants (avocado) into California. To identify likely sources and routes of entry of such pest invasions, we examined the population genetics of the most recent invader, avocado thrips [Scirtothrips perseae Nakahara (Thysanoptera: Thripidae)], using mitochondrial DNA (mtDNA) and microsatellite markers. The mtDNA sequences revealed three geographically distinct and divergent lineages, of which the mtDNA haplotypes of Californian individuals were most closely related to populations in the center of the pest's native range. Analysis of allele frequencies at four microsatellite loci added resolution, indicating Coatepec Harinas, Mexico, as the most likely source of the Californian population. Statistically, we did not detect any bottleneck in population size associated with the invasion of California. However, estimates of the effective population size of the invading population suggest that a severe bottleneck occurred, indicating that the quantity of host‐plant material entering California was small. Our findings implicate Coatepec Harinas, a large avocado germplasm and breeding center, as the most likely source of the introduced Californian population of S. perseae and as a likely source of previous and future avocado pest introductions. Efforts to identify natural enemies of S. perseae for biological control should focus on Coatepec Harinas and immediate surrounds. Moreover, identification of the source of invasive pests enables the establishment and enforcement of plant quarantine and free‐trade protocols.

Codling Moth (Lepidoptera: Tortricidae) Larval Survival under Heated Anaerobic Conditions

Quarantine regulations of importing countries are designed to prevent the introduction of exotic arthropod pests. A popular procedure is to use thermal treatments such as vapor heat, forced hot air, and hot water dips to disinfest fresh agricultural commodities (Sharp, 1994; Hallman and Armstrong, 1994; Neven, 2003). Other potential treatments involve controlled atmosphere thermal treatment systems (CATTS) (Neven and Mitcham, 1996) and radio frequency exposures in water baths (Ikediala et al, 2002; Wang et al, 2001). Wang et al. (2002) used a heating block system to determine the temperatures and exposure times required for efficacious use of heat against codling moth larvae, Cydia pomonella (L.) (Lepidoptera: Tortricidae). The predicted treatments have been verified for infested sweet cherries, Prunus avium (L.) L. (Rosaceae), by using various hot water baths (Hansen et al, 2004). Although heat is the major component for all these thermal treatments, many other abiotic factors can influence efficacy (Hansen and Sharp, 1998,2000). An obvious condition that impacts insect survival is any impediment to the vital respiration of the pest, such as in the CATTS or hot water dip treatments. However, few studies have compared treatment efficacy between aerobic and anaerobic systems. Knowledge of the contribution of asphyxiation would improve the efficacy of postharvest treatments and refine the precision of the mathematical mortality models. The objective of this study was to compare the efficacy of a thermal treatment under different oxygen-poor atmospheres by using codling moth larvae. This information would aide in the development of efficacious heat treatments.

History and Future of Introduction of Exotic Arthropod Biological Control Agents in Spain: A Dilemma?

The first documented introduction of an exotic invertebrate biological control agent (IBCA) in Spain occurred in 1908. Sixty-four additional species have been introduced since then. Information, both previously recorded and original data, on the species introduced for pest control is summarized. Most of the introduced IBCAs focused on citrus pests and homopterans clearly predominate among target phytophagous species. Success has been more frequent for IBCAs used in seasonal inoculative strategies (50.0% of cases) than in classical biological control programs (17.1% of cases). Concerns about potential non-target effects of such species are increasing, but post-release evaluation has often been insufficient to draw any conclusions about them. Most of the beneficial species introduced in Spain were parasitoids (n = 53), and the remaining species were predators (n = 12). Only four parasitoids are considered specialized monophagous natural enemies. The mean number of host species parasitized by parasitoids is 15.2, whereas the mean number of prey species attacked by predators is 21.2. Therefore, polyphagy appears to be quite common among the IBCAs that have been introduced in Spain. The rationale guiding many of these introductions in the past would not be acceptable nowadays. Since classical biological control is such a valuable strategy for pest control, straightforward protocols to evaluate exotic candidate species are urgently needed.

ASSESSING RISKS OF RELEASING EXOTIC BIOLOGICAL CONTROL AGENTS OF ARTHROPOD PESTS

More than 5000 introductions of about 2000 species of exotic arthropod agents for control of arthropod pests in 196 countries or islands during the past 120 years rarely have resulted in negative environmental effects. Yet, risks of environmental effects caused by releases of exotics are of growing concern. Twenty countries have implemented regulations for release of biological control agents. Soon, the International Standard for Phytosanitary Measures (ISPM3) will become the standard for all biological control introductions worldwide, but this standard does not provide methods by which to assess environmental risks. This review summarizes documented nontarget effects and discusses the development and application of comprehensive and quick-scan environmental risk assessment methods.

Invasibility and species richness of island endemic arthropods: a general model of endemic vs. exotic species

AbstractAim This paper has two objectives. First, we examine how a variety of biotic, abiotic and anthropogenic factors influence the endemic and introduced arthropod richness on an oceanic island. Second, we look at the relationship between the endemic and introduced arthropod richness, to ask whether areas with high levels of endemic species richness deter invasions.Location The work was carried out on a young volcanic island, Terceira, in the Azores.Methods We used standard techniques to collect data on arthropod species richness. Environmental data were obtained from the CIELO climatic model and using GIS. The explanatory value of environmental variables on a small‐scale gradient of endemic and exotic arthropod species richness was examined with generalized linear models (GLMs). In addition, the impact of both endemic and exotic species richness in the communities was assessed by entering them after the environmental variable(s) to see if they contributed significantly to the final model (the hierarchical method).Results Abiotic (climatic and geomorphological) variables gave a better explanation of the variation in endemic species richness, whereas anthropogenic variables explained most of the variation in introduced species richness. Furthermore, after accounting for all environmental variables, part of the unexplained variance in the endemic species richness is explained by the introduced species richness and vice‐versa. That is, areas with high levels of endemic species richness had many introduced species. There is evidence of a somewhat inverse spatial distribution between a group of oceanic‐type, forest‐dwelling, endemic, relict arthropods and a group of more generalist endemic arthropods that are able to survive in disturbed marginal sites particularly rich in non‐indigenous species.Main conclusions Richness of endemic species is mainly driven by abiotic factors such as a climatic axis (oceanic‐type localities with lower temperatures and summer precipitations) and a binary variable CALD (location of sites in caldeiras or ravines), whereas richness of introduced species depends on disturbance related factors. However, after factoring out these major influences, there is a correlation between endemic and introduced richness, suggesting that – independent of the environmental and geographical factors that affect the distribution of endemic or introduced species – the richest endemic assemblages are more prone to invasion, due probably to a facilitation process. Inconclusive evidence suggests that non‐indigenous species are limited to those sites under anthropogenic influence located mainly near forest edges, but the rate of expansion of those species to high‐altitude, core pristine sites has still to be tested.

Biological Control of Tropical Weeds: Research Opportunities in Plant–Herbivore Interactions1

INVASIVE EXOTIC SPECIES ARE A MAJOR ECOLOGICAL PROBLEM in many of the world's ecosystems (Sala et al. 2000). With some notable exceptions, however, most tropical moist forests appear to be resistant to the impacts of invasive exotic plants (Rejmainek 1996, Denslow & DeWalt in press). Sala et al. (2000), for example, identified land use change, but not biotic exchange, as the major threat to tropical ecosystems. However, the impacts of invasive exotic plants are a leading threat to native ecosystems on oceanic islands, where naturalized exotic plants have doubled the sizes of floras (Sax et al. 2002). On tropical islands, exotic species invade intact forests, alter successional trajectories, impede restoration of endangered plant communities, and contribute to the degradation of fragmented ecosystems (Denslow & DeWalt in press). These impacts are of special concern because tropical islands are repositories of great biodiversity and are characterized by high levels of endemism and large numbers of threatened and endangered species. Furthermore, continental tropical forests that are fragmented or otherwise disturbed also are vulnerable to the impacts of exotic invaders (e.g., Humphries et al. 1992), and control of invasive exotic plants is a major cost for many land managers. Unfortunately, the options available for management of established invasive species are few and costly and carry risk of unintended consequences. A tool with great promise is the introduction of exotic hostspecific arthropods or pathogens to reduce the abundance, rate of spread, and/or habitat distribution of the target plant in its invasive range. Classical biological control is based on the premise that the population explosions of some exotic species in their introduced ranges are due in part to their escape from their native herbivoresthe ecological release hypothesis (Keane & Crawley 2002, DeWalt etal. 2004, Levine etal. 2004). Historically, the primary objective of weed biocontrol has been the direct reduction in density, cover, and range of target weeds that suppress desirable forage species, are toxic or unpalatable to livestock or that impede waterways. Most of this experience has developed in nonforest ecosystems (Coombs et al. 2004) and at temperate as opposed to tropical latitudes; among weed genera targeted by biocontrol worldwide (except Australia which has both tropical and nontropical ecosystems), 51 percent have been exclusively nontropical and only 25 percent exclusively tropical (Julien & Griffiths 1998). In some cases, this approach has met with dramatic success, e.g., St. John's wort: Hypericumperforatum L. (Harris et al. 1969), leafy spurge: Euphorbia esula L. (Harris 1993), various cactus species: Opuntia spp. (e.g., Moran & Zimmermann 1991), water hyacinth: Eichornia crassipes (Martius) Solms-Laubach (Center et al. 1999b), and giant salvinia: Salvinia molesta D. S. Mitchell (Room et al. 1981). The use of introduced arthopods and pathogens to control exotic wildland weeds is more recent but is showing promise in the control of paperbark: Melaleuca quinquenervia (Cav.) Blake in the Florida Everglades (Center et al. 2000), purple loosestrife: Lythrum salicaria L. in the northern (U.S.) wetlands (Blossey 2002), saltcedar: Tamarix spp. along western (U.S.) stream courses (DeLoach & Carruthers 2004), and several Acacia species in South Africa (Impson et al. 2000). Concern has been expressed over the use of biocontrol agents because of their potential to cause'both direct and indirect nontarget impacts (Simberloff & Stiling 1996; Louda et al. 1997, 2003; McEvoy & Coombs 2000). Nontarget impacts of introduced biocontrol agents for weeds can take the form of direct feeding by the agent on nontarget plant species (Pemberton 2000) or indirect interactions such as competition with native herbivores (Louda et al. 1997) and alteration of the community trophic structure (Henneman & Memmott 2001). Recent reviews provide evidence that the risk of direct nontarget impacts is greatest in closely related species and that the agents released following modern, widely accepted host-range testing protocols and review processes rarely affect nontarget species (Pemberton 2000). However, only a small proportion of agents released are effective at reducing the target species, and our understanding of indirect interactions of introduced biocontrol agents is rudimentary (McEvoy & Coombs 2000). As our appreciation grows of the harm caused by invasive plants in native ecosystems, the use of biological control agents in wildlands becomes increasingly attractive. Extensive use of chemical and mechanical control methods in native ecosystems also can have substantial secondary effects, including impacts on nontarget species and ecosystem processes. In addition to their high host specificity, biocontrol agents can be effective over large areas of poorly accessible terrain. In many tropical countries, where available resources-both financial and human-for the long-term control of invasive species in natural areas are small, cost-effectiveness makes biological control an attractive conservation tool. 1 Received 3 March 2005; revision accepted 17 June 2005. 2 Corresponding author; e-mail: jdenslow@fs.fed.us

Containment of Arthropod Disease Vectors

Effective containment of arthropod vectors of infectious diseases is necessary to prevent transmission of pathogens by released, infected vectors and to prevent vectors that escape from establishing populations that subsequently contribute to increased disease. Although rare, past releases illustrate what can go wrong and justify the need for guidelines that minimize risks. An overview of recommendations for insectary facilities, practices, and equipment is provided, and features of four recently published and increasingly rigorous arthropod containment levels (ACLs 1-4) are summarized. ACL-1 is appropriate for research that constitutes the lowest risk level, including uninfected arthropods or vectors that are infected with micro-organisms that do not cause disease in humans, domestic animals, or wildlife. ACL-2 is appropriate for indigenous and exotic arthropods that represent a moderate risk, including vectors infected or suspected of being infected with biosafety level (BSL)-2 infectious agents and arthropods that have been genetically modified in ways that do not significantly affect their fecundity, survival, host preference, or vector competence. ACL-3 is recommended for arthropods that are or may be infected with BSL-3 infectious agents. ACL-3 places greater emphasis on pathogen containment and more restricted access to the insectary than ACL-2. ACL-4 is intended for arthropods that are infected with the most dangerous BSL-4 infectious agents, which can cause life-threatening illness by aerosol or arthropod bite. Adherence to these guidelines will result in laboratory-based arthropod vector research that minimizes risks and results in important new contributions to applied and basic science.

REGULATORY ENTOMOLOGY AND BIOLOGICAL CONTROL: A TRIBUTE TO REECE SAILER

Dr. Reece I. Sailer joined the faculty of the Entomology and Nematology Department, University of Florida, Institute of Food and Agricultural Sciences in early 1973, an opportune time to conduct biological control research (Fig. 1). He entered arguably the nations largest entomological community with a well-developed research and regulatory infrastructure. His research in insect biological control required taxonomists to provide authoritative identifications and an associated library, well-curated collections of specimens identified to species, and a secure building with limited access to contain exotic arthropods and arthropod pathogens. I committed my career to the creation of this kind of infrastructure for Florida and, with the help of a dedicated staff, obtained and managed many of the resources that supported Dr. Sailer. This work began 49 years ago, in July 1953, when I left the Entomology Department of the University of Florida and accepted a position as an Entomologist in the Entomology Bureau of the State Plant Board (SPB). I had been teaching biological control and apiculture, and was interested in insect taxonomy. Ed Ayers, the recently appointed Plant Commissioner, directed me to build an Entomology Bureau with an extensive insect collection and a regulatory capability second to no other state. Al-

Restoring Balance: Using Exotic Species to Control Invasive Exotic Species

Abstract: Invasive species threaten natural habitats worldwide, and active human management is required to prevent invasion, contain spread, or remediate ecosystems following habitat degradation. One powerful technology for invasive species management in sensitive habitats is biological control, the use of carefully selected upper‐trophic‐level organisms that utilize the exotic pest as a resource, thereby reducing it to less harmful densities. Many in the conservation biology community view this pest‐management technology as a high‐risk enterprise because of potential collateral damage to nontarget species. The potential benefits arising from successful biological programs are reduced pesticide use, significant pest suppression, and a return to ecological conditions similar to those observed before the arrival of the pest. Biological control as a pest‐management strategy has limitations: some pest species may not be suitable targets for biological control because natural enemies may not be sufficiently host‐specific and may pose a threat to nontarget organisms. In some instances, substantial effects on nontarget species have occurred because generalist natural enemies established as part of a biological control program heavily utilized other resources in addition to the target pest. To minimize nontarget impacts, regulations governing releases of natural enemies are becoming more stringent, as evidenced in New Zealand and Australia. Voluntary codes of good practice are being advocated by the Food and Agriculture Organization to promote wide adoption of safety measures, which, if followed, should result in the selection of agents with high levels of host and habitat fidelity. Biological control programs in support of conservation have traditionally targeted weed species that threaten natural areas. More recently, exotic arthropod pests that compete with native wildlife or damage native plants have become targets of conservation‐oriented biological control programs. Extension of biological control to new targets of conservation importance, such as invasive aquatic invertebrates and pestiferous vertebrates, is warranted. In many instances, once prevention, containment, and eradication options have been exhausted or deemed infeasible, carefully orchestrated biological control programs against appropriately selected targets may be the only feasible way to control invasive species affecting communities under assault from exotic species.

Terrestrial Arthropods as Indicators of Ecological Restoration Success in Coastal Sage Scrub (California, U.S.A.)

Abstract Ecological restoration enjoys widespread use as a technique to mitigate for environmental damage. Success of a restoration project often is evaluated on the basis of plant cover only. Recovery of a native arthropod fauna is also important to achieve conservation goals. I sampled arthropod communities by pitfall trapping in undisturbed, disturbed, and restored coastal sage scrub habitats in southern California. I evaluated arthropod community composition, diversity, and abundance using summary statistics, cluster analysis, and detrended correspondence analysis (DCA) and investigated influence of vegetation on arthropod communities with multiple regression analysis. Arthropod diversity at undisturbed and disturbed sites was greater than at sites that were 5 and 15 years following restoration ( p < 0.05). Number of arthropod species was not significantly different among undisturbed, disturbed, and restored sites, and two restoration sites had significantly more individuals than other sites. Vegetation at disturbed and undisturbed sites differed significantly; older restorations did not differ significantly from undisturbed sites in diversity, percent cover, or structural complexity. In multiple regression models, arthropod species richness and diversity was negatively related to vegetation height but positively related to structural complexity at intermediate heights. Exotic arthropod species were negatively associated with overall arthropod diversity, with abundance of the earwig Forficula auricularia best predicting diversity at comparison (not restored) sites (r2 = 0.29), and abundance of the spider Dysdera crocata and the ant Linepithema humile predicting diversity at all sites combined (r2 = 0.48). Native scavengers were less abundant at restored sites than all other sites and, with a notable exception, native predators were less abundant as well. DCA of all species separated restored sites from all other sites on the first axis, which was highly correlated with arthropod diversity and exotic arthropod species abundance. Lower taxonomic levels showed similar but weaker patterns, with example families not discriminating between site histories. Vegetation characteristics did not differ significantly between the newly restored site and disturbed sites, or between mature restoration sites and undisturbed sites. In contrast, arthropod communities at all restored sites were, as a group, significantly different from both disturbed and undisturbed sites. As found in other studies of other restoration sites, arthropod communities are less diverse and have altered guild structure. If restoration is to be successful as compensatory mitigation, restoration success standards must be expanded to include arthropods.

Introduction of nonindigenous arthropod pests of animals.

A variety of pathways exist for the introduction of nonindigenous insects, ticks, and mites of veterinary importance into the United States. The most prominent includes the natural migration of mosquitoes and flies by the flight of adults, ectoparasites entering the country on wildlife transport hosts, and accidental introductions on animals legally imported through United States Department of Agriculture (USDA) quarantine facilities. Examples of the establishment and subsequent eradication of exotic pests of livestock are presented to illustrate the critical role of the USDA in protecting American agriculture with particular emphasis on the southern cattle tick, Boophilus microplus (Canestrini), the cattle tick, B. annulatus (Say), and the screwworm, Cochliomyia hominivorax (Coquerel). Priority group rating of nonindigenous arthropod pests and disease vectors are discussed. Although the primary responsibility for preventing the introduction and establishment of arthropods that affect livestock and poultry rests on the shoulders of USDA professionals, insect surveys by extension entomologists along with observations by research specialists and producers are also important in detecting exotic arthropod species. Animal health professionals from all sectors of the livestock and poultry industries may well be the first line of defense from the introduction of nonindigenous arthropods and the diseases they transmit.

Specialization of Phytophagous Arthropod Communities on Introduced Plants

Arthropod herbivore communities vary in the proportion of plant family specialists and broad generalists. Examination of the literature of 23 annual crop plant species and the associated feeding relations of 498 arthropod species in Japan revealed that contemporary cropping area was only weakly associated with current arthropod species richness and that the proportion of plant family specialists was greater and the proportion of generalists was lower on plant species that had been in Japan for longer periods of time. These results suggest that arthropod communities become increasingly more specialized or less generalized the longer a plant coexists with the community, and that this process can occur over time periods of a few thousand years. Exotic arthropod species associated with these plants and known to have invaded Japan in the last 100—200 yr are more generalized than the native fauna, so species invasions could not contribute to the increased specialization or decreased generalization with time.