A role for molecular genetics in the recognition and conservation of endangered species.

Taxonomies based on morphological traits alone sometimes provide inadequate or misleading guides to phylogenetic distinctions at the subspecies and species levels. Yet taxonomic assignments inevitably shape perceptions of biotic diversity, including recognition of endangered species. Case histories are discussed in which the data of molecular genetics revealed prior systematic errors of the two possible kinds: taxonomic recognition of groups showing little evolutionary differentiation, and lack of taxonomic recognition of phylogenetically distinct forms. In such cases, conservation efforts for 'endangered species' can be misdirected with respect to the goal of protecting biological diversity

The best and the worst of times for evolutionary biology

The 21st century will offer great opportunities, but also challenges, for the field of evolutionary biology, particularly in areas related to molecular genetic technologies, the environment, biodiversity, and public education. The coming decades promise to be both the best and the worst of times for the evolutionary disciplines

Considerations on the evolution of qualitative multistate traits

Simple models for the evolution of qualitative multistate traits are considered, in which the traits are permitted to evolve in time-dependent versus speciation-dependent fashion. Of particular interest are the means and variances of distances for these traits in evolutionary phylads characterized by different rates of speciation, when alternative characters are neutral with respect to fitness, and when the total number of observable characters is limited to small values. As attainable character states are increasingly restricted, mean distance (D) in a phylad decreases, regardless of whether evolution is a function of time or of rate of speciation. The ratio of mean distances in species-rich and species-poor phylads of comparable evolutionary age (DR/DP) remains near one when differentiation is proportional to time, even when attainable character states are severely restricted. DR/DP also nears one as a result of restricting character states when differentiation is proportional to rate of speciation, but the effect is not severe unless the number of character states is very small and the probability of change per speciation very large. These and other results are discussed with reference to available data sets on qualitative multistate traits. © 1979 Leiden University Press

Identification of Birds through DNA Barcodes

Short DNA sequences from a standardized region of the genome provide a DNA barcode for identifying species. Compiling a public library of DNA barcodes linked to named specimens could provide a new master key for identifying species, one whose power will rise with increased taxon coverage and with faster, cheaper sequencing. Recent work suggests that sequence diversity in a 648-bp region of the mitochondrial gene, cytochrome c oxidase I (COI), might serve as a DNA barcode for the identification of animal species. This study tested the effectiveness of a COI barcode in discriminating bird species, one of the largest and best-studied vertebrate groups. We determined COI barcodes for 260 species of North American birds and found that distinguishing species was generally straightforward. All species had a different COI barcode(s), and the differences between closely related species were, on average, 18 times higher than the differences within species. Our results identified four probable new species of North American birds, suggesting that a global survey will lead to the recognition of many additional bird species. The finding of large COI sequence differences between, as compared to small differences within, species confirms the effectiveness of COI barcodes for the identification of bird species. This result plus those from other groups of animals imply that a standard screening threshold of sequence difference (10× average intraspecific difference) could speed the discovery of new animal species. The growing evidence for the effectiveness of DNA barcodes as a basis for species identification supports an international exercise that has recently begun to assemble a comprehensive library of COI sequences linked to named specimens

Catadromous eels continue to be slippery research subjects.

As adults, Atlantic eels (Anguilla rostrata in the Americas and Anguilla anguilla in Europe) are tubular slime-covered fish that spend most of their catadromous life-cycle in coastal environs before swimming far out to sea to reproduce, as part of an intergenerational migratory circuit that provides an interesting reversal of the pattern displayed by adult anadromous salmon that live mostly in the ocean but then migrate long distances to spawn in freshwater streams. Earlier genetic findings on Atlantic eels involved specimens collected across their broad continental ranges and generally indicated that conspecifics probably engage in panmictic or quasi-panmictic spawning,from which arise leaf-shaped leptocephaus larvae that then disperse back to coastal locations more or less at random with respect to the widespread geographical origins of the parental genes they carry. In this issue, Alset al. (2011) add exciting information about this peculiar life-history pattern of catadromous Atlantic eels by extending the genetic analyses to eel larvae collected from the Sargasso Sea, the oceanic area where both species spawn. Results help to confirm standard textbook wisdom that these catadromous eels are nearly unique in the biological world by having both broad geographical distributions and yet displaying intraspecific near panmixia

Colloquium paper: three ambitious (and rather unorthodox) assignments for the field of biodiversity genetics.

The field of molecular genetics has many roles in biodiversity assessment and conservation. I summarize three of those standard roles and propose logical extensions of each. First, many biologists suppose that a comprehensive picture of the Tree of Life will soon emerge from multilocus DNA sequence data interpreted in concert with fossils and other evidence. If nonreticulate trees are indeed valid metaphors for life's history, then a well dated global phylogeny will offer an opportunity to erect a universally standardized scheme of biological classification. If life's history proves to be somewhat reticulate, a web-like phylogenetic pattern should become evident and will offer opportunities to reevaluate the fundamental nature of evolutionary processes. Second, extensive networks of wildlife sanctuaries offer some hope for shepherding appreciable biodiversity through the ongoing extinction crisis, and molecular genetics can assist in park design by helping to identify key species, historically important biotic areas, and biodiversity hotspots. An opportunity centers on the concept of Pleistocene Parks that could protect "legacy biotas" in much the same way that traditional national parks preserve special geological features and historical landmarks honor legacy events in human affairs. Third, genetic perspectives have become an integral part of many focused conservation efforts by unveiling ecological, behavioral, or evolutionary phenomena relevant to population management. They also can open opportunities to educate the public about the many intellectual gifts and aesthetic marvels of the natural world

Evolutionary diversity and turn-over of sex determination in teleost fishes.

Sex determination, due to the obvious association with reproduction and Darwinian fitness, has been traditionally assumed to be a relatively conserved trait. However, research on teleost fishes has shown that this need not be the case, as these animals display a remarkable diversity in the ways that they determine sex. These different mechanisms, which include constitutive genetic mechanisms on sex chromosomes, polygenic constitutive mechanisms, environmental influences, hermaphroditism, and unisexuality have each originated numerous independent times in the teleosts. The evolutionary lability of sex determination, and the corresponding rapid rate of turn-over among different modes, makes the teleost clade an excellent model with which to test theories regarding the evolution of sex determining adaptations. Much of the plasticity in sex determination likely results from the dynamic teleost genome, and recent advances in fish genetics and genomics have revealed the role of gene and genome duplication in fostering emergence and turn-over of sex determining mechanisms

Conservation genetics in the marine realm

Techniques for DNA and protein assay make possible genetic studies on any species. In recent years, molecular methods have been applied to a number of conservation-relevant genetic issues for marine organisms ranging from zooplankton to whales. To introduce these symposium proceedings, I will mention some of the unusual challenges and opportunities afforded by marine taxa for genetic research in conservation. Marine organisms often are less accessible for behavioral and natural history observation than are their terrestrial counterparts. Many marine organisms have exceptional dispersal and migratory capabilities. Species' ranges can be vast. Life histories may include high fecundities and explosive reproductive potentials. Many marine species of conservation concern are harvested commercially or illegally and thus economic, social, jurisdictional, and forensic matters often arise in population management, in addition to biological considerations. For a diversity of marine taxa, molecular markers have uncovered previously unknown aspects of behavior, natural history, and population demography that can inform conservation and management decisions. The studies compiled in this volume highlight the scope and imaginative uses of genetic information for conservation challenges in the marine realm

Twenty-five key evolutionary insights from the phylogeographic revolution in population genetics

An overview is provided of 25 novel perspectives that the field of phylogeography has brought to scientific studies of population genetics and speciation. A unifying theme is that microevolu-tion can be described as an extended genealogical process played out in space and time, and reflecting the oft-idiosyncratic biological and environmental factors that have impinged on historical population demography. Most of the empirical and conceptual methods of phylogeo-graphy depart considerably from conventional equilibrium approaches, and they are helping to reorient and extend traditional population genetics in realistic directions that emphasize historical demography and genealogy