Conservation and Genetics of Populations

Abstract

F. W. Allendorf and G. Luikart. Blackwell, 2007. $84.95. This 600-page book addresses anew the genetics of populations with emphasis on conservation practices. In the introduction, the authors endeavor “to provide a thorough examination of our understanding of the genetic variation in natural populations. Based upon that foundation, we will consider the application of this understanding to the many problems faced by conservation biologists with the hope that our more informed actions can make a difference.” The book is extremely well produced and illustrated; it is also of great interest that the authors have chosen to incorporate “guest boxes,” statements or considerations by eminent investigators. These short boxes much enhance the text, and they are usually followed by a few succinct questions that relate to the text just read. The first chapter is on “Phenotypic variation in natural populations”; it successfully integrates environmental and genetic sequelae. Much appreciated here is that the authors not only cite relevant literature but also, unlike many other texts, actually explain what the quoted article had to say. Let me cite a relevant example from the discussion on “behavior”: The importance of genetically based differences in behavior for adaptation to local conditions has been shown by an elegant series of experiments with the western terrestrial garter snake (Arnold 1981). This garter snake occurs in a wide variety of habitats throughout the West of North America …. Arnold has compared the diets of snakes living in foggy and wet coastal climate of California and the drier, high elevation, inland areas …As hard as it may be to believe, the major prey of coastal snakes is the banana slug; in contrast, banana slugs do not occur at the inland sites. Arnold captured pregnant females from both locations and raised the young snakes in isolation away from their littermates and mother to remove this possible environmental influence on their behavior. The young snakes were offered a small chunk of freshly thawed banana slug. Naïve coastal snakes ate the slugs; inland snakes did not (Fig.2.8). Hybrid snakes … were intermediate …. These results confirm that the difference between populations in slug-eating behavior has a strong genetic component. Contrary to many similar texts, a large chapter on “Genetic variation in natural populations: chromosomes and proteins” follows. The impact of chromosomal variation is rarely fully considered in conservation biology, and because I have trodden this path, it is of interest to me and I regret that King's book is not referred to in this section. The authors caution, however, that “study of DNA sequences…cannot replace examination of chromosomes,” a statement that is all too often now not seriously considered. Besides, there are some errors that need correction; for example, the horse and mule (should be donkey) do not hybridize to make an infertile animal, and the Mountain zebra has 32 chromosomes, not 34 as stated. In Chapter 4, the authors review concisely the numerous techniques now employed for genetic analysis, from a historical perspective, with excellent examples, and all relevant to conservation issues. There are polymerase chain reaction, minisatellites, single nucleotide polymorphisms, microarrays, the genome, and everything else one needs to know to assess genetic variability of populations, of animals and plants. They also make the bold prediction that methodologies will become cheaper, faster and that genetics will make an ever greater impact on conservation issues. Their questions to students at the end of this chapter are especially challenging. Subsequent chapters are more predictable for such a book; what is particularly helpful in these mathematical considerations is that the authors bring actual examples from the field and literature that exemplify the problems to be solved. They discuss the Hardy–Weinberg principle, how to estimate the effective population size, and then they come to “Natural selection” in Chapter 8. Because many good examples come from the plant kingdom, they discuss these in greater detail, consider the effects of single and multiple allelic changes, and of course present the dark- and light-colored pocket mice. Considerations on population genetics, drift, and quantitative genetics are followed by the effect of mutations and their evolutionary consequences. Perhaps, because of my personal interest, it seems that the frequency and importance of chromosomal rearrangements in evolution are under-discussed because, for speciation, they play a major role. Part III of the book reviews “Genetics and conservation.” This part of the book is clearly an aspect that will be of greatest interest for many readers, and it was also the apparent reason for the senior author to undertake this writing. Here, we come to familiar topics of conservation, such as inbreeding depression, bottlenecks, conservation of species by breeding in zoos, restor