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Genes and extinction

GENETICS AND THE EXTINCTION OF SPECIES·Editors – Laura F Landweber and Andrew P Dobson·Princeton University Press·Princeton·New Jersey· USA·1999·pp189

Published: Monday 15 January 2001

-- EVEN AS human-induced extinction depletes the Earth's biodiversity, frantic efforts are on to minimise this depreciation. Many see the science of genetics as a genie that can be commanded to fabricate extinct creatures out of fossils. This book quells such misconceptions. This compilation of scientific papers exorcises such sensationalistic myths and reexamines the role of genetics in conservation biology in a pragmatic manner.

The book begins by discussing the major contributors to the loss of biodiversity. Anthropogenic factors such as unrestrained land development reduce the habitat area and quality and fragment the remaining land into discontinuous 'islands'. In effect, compartmentalisation of many endangered species occurs, making them more vulnerable to extinction.

As far as endangered species are concerned, safety lies not just in large numbers but also in the way these numbers are clustered 100 tigers in 100 mutually insular forest patches are much worse off than 50 each in two separate reserves. The importance of genetics in captive breeding programmes and other ex-situ conservation methods is paramount. Genetics helps pinpoint the best matching pairs, scoring several points over the conventional practice of selecting specimens merely on the basis of physical health of animals.

Moving away from theorising, two chapters in the book focus on the extirpation of endemic bird species in Hawaii. The extreme geographical and evolutionary isolation of the Hawaiian Islands has left the genetic makeup of its native creatures grossly unprepared to resist the onslaught of diseases such as malaria and pox. Under the impact of avian malaria, populations have plummeted and many species have disappeared, their misfortunes compounded by continuing habitat loss due to increasing human population and introduction of alien fauna species by humans, including more than 125 avian species. It becomes imminent that ex-situ conservation and breeding programmes actively utilise dna testing. One paper on species of Hawaiian honeycreepers reveals the pattern evident in the extinction of the species. The more specialised the bird niche, the more susceptible is the species to extinction.

Conservation efforts should take into account the ultimate rather than proximate causes and formulate strategies on these lines. The concluding paper looks into the realm of extinct species in particular. Although it is not possible to churn out dinosaurs, yet genetics can greatly aid long-term population studies. Such investigations may also point out important determinants of extinction of the species, such as build-up of deleterious genes or loss of genetic diversity. Reconstruction of evolutionary history of an extinct species or population is also now possible by analysing remnant dna molecules from specimens.

It is highly technical in both content and language. This collection of academic papers is decidedly not for the general reader. At the same time, it would most definitely prove to be quite an instructive compendium for the conservation biologist.

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