Rapid evolutionary dynamics and disease threats to biodiversity

doi:10.1016/j.tree.2003.08.013

Trends in Ecology & Evolution

Volume 18, Issue 11, November 2003, Pages 589-596

https://doi.org/10.1016/j.tree.2003.08.013 Get rights and content

Abstract

Existing and emerging pathogens pose unusual challenges for conservation because of their potential to drive rapid changes in the numerical abundance and genetic composition of wild host populations. An increasing number of studies indicate that host genetic diversity plays an important role in buffering populations against widespread epidemics, and that parasites represent powerful selective agents in natural populations. The observation that infectious diseases might be both mitigated by and rapidly change the genetic composition of host populations gives new significance to the role of host genetic diversity in species conservation. Less clear is the role that pathogen evolutionary change plays in the emergence and spread of new diseases, but recent examples indicate that humans might be selecting unknowingly for rapid changes in pathogen biology through habitat fragmentation, climate shifts and environmental pollution. Although the risks they pose to endangered species are apparent, pathogens and other natural enemies can be a driving force behind species and genetic diversity in natural populations, and preserving interacting networks of coevolving populations should enable hosts to respond better to future disease threats.

Section snippets

Patterns in wild populations

Parasites are likely to be powerful selective agents in natural populations, and host species exposed to a diverse array of parasites should harbor a variety of resistance alleles or a repertoire of inducible defenses. Many studies have underscored the importance of genetic variation in host resistance in causing disease patterns in both field and experimental settings (Table 1). Parasites infecting sheep, snails, fish, moths and other animals have been implicated in the maintenance of allelic

Pathogen evolution and emerging diseases

The evolutionary potential of pathogens sets them apart from other major threats to wildlife, in part because of the unpredictable and irreversible effects of introduced diseases. Most pathogens have short generation times and large population sizes, and strong selection pressures following ecological changes might accelerate pathogen evolution. Human-imposed selection deriving from the widespread application of chemical controls is responsible largely for the emergence of drug-resistant

Full coevolutionary dynamics

Most examples from wild host–parasite systems point to neither host nor parasite evolution operating alone, but to joint coevolutionary dynamics (Table 1). Long-term studies of model host–parasite systems emphasize multiple coevolutionary processes and outcomes (see example in Box 3), including directional selection in favour of increased host resistance and shifts in parasite virulence [74], frequency-dependent selection leading to time-lagged cycles in host and parasite abundance and genotype

Consequences for biodiversity and conservation

Although habitat loss and overexploitation remain major factors in host population declines and extinctions, infectious diseases have become increasingly important factors in wildlife conservation 1, 2. ‘Virgin ground’ epidemics following novel introductions progress rapidly through previously unexposed populations, often causing high case fatality rates and stunning reductions in host abundance 5, 6. Introduced diseases have been implicated in the declines and, in some cases, extinctions of

Acknowledgements

This work was initiated as part of the ‘Disease and Conservation’ working group organized by Andy Dobson and supported by the National Center for Ecological Analysis and Synthesis, a Center funded by NSF (Grant #DEB–94–21535), the University of California at Santa Barbara, and the State of California. We thank Amy Pedersen, Leslie Real, Andrew Davis, Peter Thrall, Priyanga Amarasekare, Peter Hudson, and three anonymous reviewers for helpful discussion and comments.

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Trends in Ecology & Evolution

Rapid evolutionary dynamics and disease threats to biodiversity

Abstract

Section snippets

Patterns in wild populations

Pathogen evolution and emerging diseases

Full coevolutionary dynamics

Consequences for biodiversity and conservation

Acknowledgements

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Trends Ecol. Evol.

Trends Ecol. Evol.

Curr. Opin. Plant Biol.

Trends Ecol. Evol.

Int. J. Parasitol.

Trends Parasitol.

Adv. Virus Res.

Trends Ecol. Evol.

Trends Ecol. Evol.

Aquaculture

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