Host range expansion/evolution
Barratt B.I.P., Murney R., Easingwood R., Ward V.K. (2006).
Virus-like particles in the ovaries of Microctonus aethiopoides Loan (Hymenoptera: Braconidae): comparison of biotypes from Morocco and Europe.
Journal of Invertebrate Pathology 91: 13-18.
Virus-like particles (MaVLP) have been discovered in the ovarial epithelial cells of the solitary, koinobiont, endoparasitoid, Microctonus aethiopoides Loan (Hymenoptera: Braconidae) introduced to New Zealand originally from Morocco to control the lucerne pest Sitona discoideus Gyllenhal (Coleoptera: Curculionidae). MaVLP have been found in all females examined. It has been suggested, although not demonstrated, that like many other such VLP found in parasitoids, MaVLP might play a role in host immunosuppression. Since another biotype of M. aethiopoides from Ireland has been proposed for introduction to control the white clover pest, Sitona lepidus Gyllenhal, in New Zealand, it was considered that females from this biotype warranted transmission electron microscope examination for VLP. No VLP were observed in ovarian tissues of specimens collected from three diVerent locations in Ireland. Similarly, none were found in M. aethiopoides sourced from France, Wales, and Norway. These observations are discussed in relation to quarantine host speciWcity tests with the Irish biotype, which found that the host range of the Irish biotype is likely to be less extensive than that of the Moroccan biotype already in New Zealand.
Brodeur J. (2012). Host specificity in biological control: insights from opportunistic pathogens. Evolutionary Applications 5: 470-480.
Charles, J.G. (2011).
Using parasitoids to infer a native range for the obscure mealybug, Pseudococcus viburni, in South America.
Biocontrol 56: 155–161
An examination of the biogeographical origins and historical trade records provided an explanation as to why the obscure mealybug, Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), considered to be an American species, is not attacked by native parasitoids in the USA, whereas it is controlled in Europe by Acerophagus maculipennis (Mercet) (Encyrtidae) described from the Canary Islands (as Pseudophycus maculipennis). The hypothesis was supported that P. viburni and A. maculipennis are co-evolved Neotropical species, and that both were transported from S. America (probably Chile) to Europe via the Canary Islands possibly as early as the sixteenth century. Invasion of P. viburni into the USA occurred later, but without natural enemies. This explains why P. viburni in the USA is not attacked by native North American parasitoids and why A. maculipennis is not known to attack any mealybugs of Palaearctic origin. The hypothesis adds confidence that well conducted classical biocontrol programmes involving these taxa pose a low environmental risk to native, non-target fauna.
Desneux, N., Blahnik, R., Delebecque, C.J. and Heimpel, G.E. (2012).
Host phylogeny and specialisation in parasitoids.
Ecology Letters 5: 453-460
The authors build upon previous studies of preference- and performance-related traits on the host range of the aphid parasitoid Binodoxys communis (Hymenoptera: Braconidae) by mapping a series of these traits onto the phylogeny of the (aphid) host species. They found that both classes of traits showed phylogenetic conservatism with respect to host species.
Futuyma D.J. (1999). Potential evolution of host range in herbivorous insects. Pp. 42-53 In: Proceedings of the X International Symposium of Biological Control of Weeds, N.R. Spencer (Ed.).
Holt R.D. and Hochberg M.E. (1997). When is biological control evolutionarily stable (or is it)? Ecology 78: 1673-1683.
Hufbauer R.A. (2002). Evidence for nonadaptive radiation in parasitoid virulence following a biological control introduction. Ecological Applications 12: 66-78.
Hufbauer R.A. and Roderick G.K. (2005).
Microevolution in biological control: Mechanisms, patterns, and processes.
Biological Control 35: 227-239.
The four fundamental processes of microevolution are discussed in relation to how they interact in the context of biological control. The types of experiments that can address questions are discussed and ways of using microevolution to define risks, and enhance efficacy and safety of biological control.
Marohasy J. (1996).
Host shifts in biological weed control: real problems, semantic difficulties or poor science?
International Journal of Pest Management 42: 71-75.
Many biologists perceive organisms as constantly evolving and therefore consider the host plant ranges of biological control agents as likely to undergo adaptive changes should environmental conditions change, after successful biological control. However, despite the introduction of over 600 insect species from one geographic region to another for biological weed control during this century, there are relatively few documented cases of changes in host plant range. It is concluded that apparent additions to host range can be explained in terms of established behavioural concepts of preadaptation, threshold change resulting from host deprivation, and effects of experience (learning). The study highlights the inappropriate term 'host shift' and it is concluded that evidence from biological weed control contradicts some aspects of ecological and evolutionary theory.
Messing R.H. and Xin-Geng W. (2008).
Competitor-free space mediates non-target impact of an introduced biological control agent.
Ecological Entomology 34: 107-113
The authors show that competitor-free space is a key mechanism maintaining an apparent host shift by an introduced biocontrol agent onto a non-target species.
Tallamy D.W. (1999). Physiological issues in host range expansion. Pp. 11-26 In: Proceedings: Host specificity testing of exotic arthropod biological control agents: The biological basis for improvement in safety, N.R. Spencer (Ed.) Bozeman, Montana.
Environmental impact modelling