Background

''Conservation genetics'' has become a popular discipline, as evidenced, for example, by two edited compilations (Loeschcke et al., 1994; Avise and Hamrick, 1996), a teaching textbook (Frankham et al., 2002), and a scientific journal (initiated in 2001), all bearing within their titles that exact two-word phrase. Historically, the field was associated mostly with studies of inbreeding depression and the loss of heterozygosity in small populations, but its purview has expanded greatly in recent years to include a wide range of empirical and theoretical studies that basically attempt to illuminate how patterns of genetic diversity are distributed within and among individuals, kinship groups, populations, species, and supraspecific taxa (Avise, in press). Such investigations (typically using molecular markers) routinely include genetic appraisals of the following: plant and animal mating systems, behaviors, and natural histories; magnitudes and patterns of population structure due to past and present demographic factors; gene flow, genetic drift, and various categories of natural selection; other evolutionary phenomena such as patterns and processes of speciation, hybridization, introgression, and phylogenetics; forensic analyses of wildlife and wildlife products; and many additional genetic topics that are often highly germane to the principles and the practice of conservation biology.

All of these sentiments are standard wisdom among modern biologists. So too is the realization that a strong societal preference exists for saving species that are large, attractive, or emotionally evocative, compared with those that are small, drab, or unobtrusive. Almost inevitably, conservation efforts thus become biased toward ''charismatic megabiota'' (Clark and May, 2002). I suggest another role for conservation genetics that is somewhat more amorphous, but nevertheless has a huge potential to elicit additional public support for meaningful societal action on behalf of nature and biodiversity protection. I am referring to a compelling educational mission: to enthuse students of all ages, including the general public as well as political, social, and religious leaders, about nature's countless underappreciated marvels.

Nearly all creatures (including the ''charismatically challenged'') have fascinating natural-history stories to tell, and scientists as well as natural

294 I John C. Avise theologians for centuries have delved into nature's workings through field observations and phenotypic investigations. Yet before the advent and widespread use of molecular markers, many of nature's incredible operations remained hidden from view. Nature can now be revealed at and through this new window of molecular-level observation, and the results are often far more engrossing than might ever have been predicted.

First are the astounding findings about genomes. Even a few years ago, few scientists could have imagined that genes encoding functional RNA and protein molecules of obvious benefit to the organism would prove to constitute only a small fraction of the eukaryotic genome, and that the rest of the composite DNA sequence includes an astonishing collection of noncoding regions, regulatory modules, pseudogenes, and legions of repetitive elements, many of which are descended from selfish virus-like elements that have proliferated and jumped around the genome often at the immediate fitness expense of their hosts. A new metaphor is emerging in which each eukaryotic genome can be viewed, in effect, as a miniature ecological community whose quasi-independent members (unlinked DNA sequences) all struggle for representation in the next generation of sexual reproducers and thereby become involved in elaborate coevolutionary games that can be quite analogous to the parasitisms, commensalisms, and mutualisms routinely observed among species in natural ecosystems (Avise, 2001). This metaphor of the genome as a submicroscopic community of genes constantly undergoing evolutionary adjustments is far from perfect, but it does promote a perspective on genomic operations that today may be much more useful and research-stimulating than earlier genomic metaphors (such as the ''beads on a string'' image of functional and fully collaborative genes packed tightly along chromosomes).

A second arena in which molecular genetic markers are having a huge scientific impact is in uncovering heretofore hidden secrets about the ecologies, behaviors, natural histories, and evolution of organisms in nature. An adequate discussion of this topic is far beyond the scope of this chapter, so what follow are merely a few examples of the many types of questions that scientists have answered using molecular markers, but that for one logistical reason or another had been inadequately addressed by earlier field observations or phenotypic assessments. For fuller answers to the following questions and many others like them, all in layperson language, see Avise (2002, 2006).

How big and old can natural clones of mushrooms become? (Living members of one clone were estimated to weigh a collective 100 tons, occupy 40 acres, and derive from a single zygote that formed «1,500 years ago.) Does each female green turtle (a highly migratory marine species) return to her natal beach to nest? (Yes, normally.) Why do female roly-poly pill bugs often greatly outnumber males? (Because many strains are

Three Ambitious Assignments for the Field of Biodiversity Genetics / 295

infected by intracellular parasitic bacteria that are maternally transmitted and, accordingly, have evolved the physiological capability to transform male roly-polys into functional females.) Does a pregnant male pipefish or seahorse often carry a brood of offspring from more than one dam? (In some species, yes; in other cases, no.) What fraction of embryos in the nests of bluegill sunfish are foster progeny attributable to cuckoldry by sneaker males? (Approximately 20% in one well-studied population.) Did the bipedal hop arise once or multiple times in kangaroos' evolution? (Probably once only, according to phylogenetic analysis.) Why do king crabs have an asymmetrically twisted abdomen? (Because this trait appears to be a phylogenetic legacy retained from hermit crab ancestors whose coiled abdomens had evolved to fit nicely into deserted snail shells that hermits adopt as protective homes.) Which came first in evolution, the chicken or the egg? (The hard-shelled egg came first, by «300 million years.)

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