84 0169-5347/99/$ – see front matter © 1999 Elsevier Science. All rights reserved. PII: S0169-5347(98)01564-X TREE vol. 14, no. 3 March 1999 Conservation policy There is no doubt that the insights provided by disease modelling have sharpened our understanding of infec- tion dynamics. The importance of devel- oping theoretical strategies to solve ap- plied problems is also evident. However, whenever a specific practical problem is being addressed, there lies a danger that policy makers will attempt to apply models uncritically. In this respect, it is reassuring that Courchamp and Sugihara 2 make it clear that their study is a prelimi- nary theoretical investigation and raise extensive caveats about the use of patho- gens as agents for biological control on oceanic islands. The assumption that eradication of introduced species is the best way to protect island fauna and flora might not always be true. On Kerguelen Islands, for example, rabbits and rats might do more harm than cats, in which case, control of cats might be preferable to eradication. In these circumstances, should cat con- trol even be considered without applying simultaneous programmes for rats and rabbits? Although the title of the paper 2 refers to protection of island species from extinction, it is not clear which bird species are threatened by extinction or the severity of the threat. A related issue concerns the need to identify conser- vation priorities. For example, is the goal to protect endangered species from ex- tinction or to restore island ecosystems? Eradication priorities need to be based on benefits that will arise, and not on damage already done. Many questions remain to be an- swered before we can be confident about the potential value of pathogens for alien predator control. Courchamp and Sugihara’s study is a useful first step in the theoretical exploration of the problem and demonstrates both the limitations and value of a modelling approach. Re- sults of models inevitably reflect the quality of the available data sets. For ani- mal diseases, these are often sparse and are usually based on experimental infec- tions that might bear little similarity to nature. However, one of the principal functions of models is to highlight critical gaps in knowledge. In this case, results showing the importance of natural im- munity in island populations provide a clear stimulus for further study. Con- servation problems rarely have simple answers, and mathematical models have an important role to play in identifying critical processes and parameters. Acknowledgements We would like to thank Dr Dan Haydon and Dr Marc Artois for useful discussions. Sarah Cleaveland Centre for Tropical Veterinary Medicine, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian, UK EH25 9RG (sarah.cleveland@ed.ac.uk) Simon Thirgood Game Conservancy Trust, Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh, UK EH9 3JT (simon.thirgood@ed.ac.uk) Karen Laurenson Centre for Tropical Veterinary Medicine, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian, UK EH25 9RG (karen.laurenson@ed.ac.uk) References 1 Atkinson, I.A.E. (1989) Introduced animals and extinctions, in Conservation for the Twenty-First Century (Western, D. and Pearl, M.C., eds), pp. 54–75, Oxford University Press 2 Courchamp, F. and Sugihara, G. (1999) Modeling the biological control of an alien predator to protect island species from extinction, Ecol. Appl. 9, 112–123 3 Chappuis, J.L., Bousses, P. and Barnaud, G. (1994) Alien mammals, impact and management in the French sub-Antarctic islands, Biol. Conserv. 67, 97–104 4 Flux, J.E.C. (1993) Relative effects of cats, myxomatosis, traditional control, or competitors in removing rabbits from islands, N. Z. J. Zool. 20, 13–18 5 Bloomer, J.P. and Bester, M.N. (1992) Control of feral cats on sub-Antarctic Marion Island, Indian Ocean, Biol. Conserv. 60, 211–219 6 Thorne, E.T. and Williams, E.S. (1998) Disease and endangered species: the black-footed ferret as a recent example, Conserv. Biol. 2, 66–74 7 Woodroffe, R. and Ginsberg, J.R. (1997) Past and future causes of wild dogs’ population decline, in The African Wild Dog: Status Survey and Conservation Action Plan (Woodroffe, R., Ginsberg, J. and Macdonald, D., eds), pp. 124–138, IUCN (World Conservation Union), Gland, Switzerland 8 Van Riper, C., III et al. (1986) The epizootiology and ecological significance of malaria in Hawaiian land birds, Ecol. Monogr. 56, 327–344 9 Berger, L. et al. (1998) Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America, Proc. Natl. Acad. Sci. U. S. A. 95, 9031–9036 10 Fromont, E. et al. (1997) Modelling the feline leukaemia virus (FeLV) in natural populations of cats (Felis catus), Theor. Popul. Biol. 52, 60–70 11 Courchamp, F. et al. (1995) Population dynamics of feline immunodeficiency virus within cat populations, J. Theor. Biol. 175, 553–560 NEWS & COMMENT T he third CNRS–Jacques Monod Con- ference on evolutionary biology was held at Roscoff, France (October 1998), under the Presidency of Georges Periquet (Université François Rabelais, CNRS, Tours, France). The 47 talks presented a very wide range of topics in line with the meeting’s subtitle: the evolutionary theory at the dawn of the Millennium. Further- more, many talks crossed topic bound- aries, an approach likely to be the key to any new synthesis. Marie Louise Cariou (CNRS, Gif-sur- Yvette, France) described how gene du- plications might have been critical in the evolution of amylase genes in Drosophila. Amy and Amyrel genes show different patterns of phylogenetic divergence, re- flecting the evolution of differences in expression and function. Diethard Tautz (Zoology Institute, Munich, Germany) dis- cussed attempts to detect fast-evolving genes by examining sequence divergence, from random cDNA libraries, across spe- cies of Drosophila for clones that reflect embryonically expressed genes. The small number of apparently fast-evolving genes tended to show novel expression domains in early development, giving rise to specu- lation about their role in adaptive evo- lution and the likelihood of their detec- tion in conventional assays. Both these papers led to healthy discussions about the difficulty of distinguishing between the involvement of positive selection, as against relaxed constraints. Novelty and constraint were to prove recurring themes at the meeting. An early session covered developmen- tal topics. Bas Zwaan (University College, London, UK) analysed latitudinal clines in size of Drosophila flies on different continents. Focusing on the wing blade indicated that wing size is the target of selection, rather than its components of cell size or number. Paul Brakefield (Institute of Evolutionary and Ecological Sciences, Leiden University, The Nether- lands) and Sean Carroll (Howard Hughes Medical Institute, University of Wisconsin, USA) described developmental and gen- etical research using the model system Towards a new synthesis