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The major radiations that punctuate angiosperm evolution are often associated with innovations in floral architecture. The field of plant developmental evolution seeks to understand the generation of this diversity using comparative genetic approaches that build on work done in model species such as Arabidopsis. This strategy has been particularly successful when applied to the genetic program controlling floral organ identity, but is also making advances in the area of floral symmetry. As useful as the “candidate gene” approach has been, alternatives are required to investigate morphological phenomena that are not represented in model species. Other options include methods based on quantitative trait loci and DNA sequencing, which have the additional benefit of facilitating the development of new model species. The combination of all of these approaches across a wide range of species has the potential to elucidate the genetic underpinnings of both recent and ancient radiations of flowering plants.
Managing ecosystems for resilience—the capacity to maintain function in response to perturbation—is among the most pressing ecological and socioeconomic imperatives of our time. The variability of biological and ecological systems at multiple scales in time and space makes this task even more challenging, yet diverse ecological systems often display striking regularities. These regularities often take the form of scaling laws, which describe how the structure and function of the system change systematically with scale. In this article, we review recent work on the scaling of human settlement sizes and fertility as well as the size distributions of forests. We demonstrate that systematic departures from expected ecological scaling relationships may indicate particular structuring processes (e.g., fire) or the perturbation and reorganization of ecosystems. In sum, we argue that scaling provides a powerful tool for understanding resilience and change in ecological systems.
It is widely known that birds are sensitive to ultraviolet (UV) light, and that they use UV reflecting signals in choosing mates. This led to the proposal that UV signals in birds may represent private channels of communication hidden from predators, because most mammalian predators of birds are unlikely to see UV light. This idea has held great sway with researchers and the public, sustained no doubt by human fascination with an area of communication invisible to us. However, the primary predators of songbirds are often birds of prey that can see UV light, shedding doubt on the idea that UV reflecting patterns represent “special” signals. A range of recent studies, including mate-choice experiments, models of visual processing, and comparative analyses, have claimed to provide support for and against the theory that UV signals are special. We summarize the evidence for and against this idea and conclude that, while further work is required, current evidence generally does not favor this hypothesis. We finish with suggestions for future work to settle the controversy.
Wild tigers are in a precarious state. Habitat loss and intense poaching of tigers and their prey, coupled with inadequate government efforts to maintain tiger populations, have resulted in a dramatic range contraction in tiger populations. Tigers now occupy 7 percent of their historical range, and in the past decade, the area occupied by tigers has decreased by as much as 41 percent, according to some estimates. If tigers are to survive into the next century, all of the governments throughout the species' range must demonstrate greater resolve and lasting commitments to conserve tigers and their habitats, as well as to stop all trade in tiger products from wild and captive-bred sources. Where national governments, supported in part by NGOs (nongovernmental organizations), make a consistent and substantial commitment to tiger conservation, tigers do recover. We urge leaders of tiger-range countries to support and help stage a regional tiger summit for establishing collaborative conservation efforts to ensure that tigers and their habitats are protected in perpetuity.
A survey of biology departments in 1990 led to publication of a de facto curriculum for the training of undergraduate biology majors. Knowledge of the biological sciences has changed considerably since then, and the present study attempts to find out whether or not undergraduate requirements have changed as a result. In fact, little has changed, although the molecular areas of biology are more likely to be required now than they were in 1990. In the absence of a national accrediting body for biology, questions remain about whether there needs to be a standardized curriculum and, if so, what it should contain. This study includes a look at what courses are offered by undergraduate departments, what courses are required for a biology degree, and what content is covered in the introductory course sequence. Suggestions for an updated curriculum are also provided.
The paleontological record of mammals offers many examples of evolutionary change, which are well documented at many levels of the biological hierarchy—at the level of species (and above), populations, morphology, and, in ideal cases, even genes. The evolutionary changes developed against a backdrop of climatic change that took place on different scales, from rapid shifts in climate state that took only a few decades, to those that occurred over a millennial scale, to regular glacial–interglacial transitions with cycles of roughly a hundred thousand years, to long-term warming or cooling trends over hundreds of thousands to millions of years. Are there certain scales of climatic change that accelerate evolution? And what will the current global warming event do to evolutionary rates? Here we use paleontology—the study of fossils—to illustrate the scientific method behind answering such complex questions, and to suggest that current rates of global warming are far too fast to influence evolution much and instead are likely to accelerate extinctions.