Showing papers in "BioScience in 1988"

Carbon Isotopes in PhotosynthesisFractionation techniques may reveal new aspects of carbon dynamics in plants

Abstract: he efficiency of photosynthesis continues to interest biochemists, biologists, and plant physiologists. Scientists interested in CO2 uptake are concerned about the extent to which the uptake rate is limited by such factors as stomatal diffusion and the chemistry of the CO2 absorption process. The fractionation of carbon isotopes that occurs during photosynthesis is one of the most useful techniques for investigating the efficiency of CO2 uptake. Atmospheric carbon dioxide contains approximately 1.1% of the nonradioactive isotope carbon-13 and 98.9% of carbon-12. During photosynthesis, plants discriminate against C because of small differences in chemical and physical properties imparted by the difference in mass. This discrimination can be used to assign plants to various photosynthetic groups. The isotope fractionation also reflects limitations on photosynthetic efficiency imposed by the various diffusional and chemical components of CO2 uptake. When analyzed in detail, this fractionation provides information .about water use efficiency and indicates that different strategies are needed for improving wateruse efficiency in different kinds of plants. Isotope fractionation in simple physical and chemical processes is well understood and is commonly Current studies include

Alteration of North American streams by beaver

Abstract: organic matter in the channel, create and maintain wetlands, modify nutrient cycling and decomposition dynamics, modify the structure and dynamics of the riparian zone, influence the character of water and materials transported downstream, and ultimately influence plant and animal community composition and diversity (Naiman and Melillo 1984, Naiman et al. 1986). In addition to their importance at the ecosystem level, these effects have a significant impact on the landscape and must be interpreted over broad spatial and temporal scales as beaver population dynamics shift in response to disturbance, food supply, disease, and predation. Although once more prevalent than they are today, beaver-induced alterations to drainage networks are not localized or unusual. Where beaver

New Computer Models Unify Ecological TheoryComputer simulations show that many ecological patterns can be explained by interactions among individual organisms

Abstract: biology. First, models often combine many individual organisms and assume that they can be described by a single variable, such as population size. This procedure violates the biological principle that each individual is different, with behavior and physiology that result from a unique combination of genetic and environmental influences. Second, most models do not distinguish among organisms'

Landform Effects on Ecosystem Patterns and Processes

Abstract: U nderstanding the form, behavior, and historical context of landscapes is crucial to understanding ecosystems on several temporal and spatial scales. Landforms, such as floodplains and alluvial fans, and geomorphic processes, such as stream erosion and deposition, are important parts of the setting in which ecosystems develop and material and energy flows take place. Over the long term, geomorphic processes create landforms; over a shorter term, landforms are boundary conditions controlling the spatial arrangement and rates of geomorphic processes. Ecosystems respond to both landforms and geomorphic processes. The history of geomorphic processes may be expressed directly in the composition and structure of vegetation, where geomorphic events and vegetation develop together. Geomorphic processes operating before the establishment of existing vegetation, or those subtly coexisting with the vegetation, may have their greatest influence on vegetation through controlling patterns of soil properties across a landscape, as in toposequences

Large Mammals and Process Dynamics in African EcosystemsHerbivorous mammals affect primary productivity and regulate recycling balances

Abstract: emphasized the balances among trees, shrubs, and grasses as factors both influencing and influenced by large mammals (Lamprey 1963, McNaughton and Georgiadis 1986) Estimates of energy flow through food webs were an early contribution of this research (Lamprey 1964), but only recently have investigators begun to consider how large mammals can control such ecosystem processes as energy flow and nutrient cycling (Botkin et al 1981, Frost 1985, McNaughton 1976, 1979a, 1985) Research reveals that African ecosystems are highly interactive; they cannot be understood without close

Consumer Control of Lake ProductivityLarge-scale experimental manipulations reveal complex interactions among lake organisms

Abstract: here is no common currency for ecological interactions. For example, the consumption of a small fish by a larger one entails all the following characteristics: behavioral interplay during pursuit and capture, an instantaneous reduction of the prey population, greater reproductive potential for the predator, a flux of organic energy, and a transfer of mineral nutrients such as phosphorus and nitrogen. Thus the same event is viewed differ-

Ecological Consequences of Prairie Dog Disturbances

Abstract: Prairie dogs (Figure 1) are large (approximately 1 kg as adults), herbivorous rodents that burrow and live colonially. Historically, the most abundant and widely distributed species, the black-tailed prairie dog (Cynomys ludovicianus), was common throughout the shortand mixed-grass prairies of the Great Plains. It is impossible to estimate accurately the average size or density of prairie dog colonies in presettlement times, but they covered about Figure 1. Black-tailed prairie dogs (Cynomys ludovicianus) on a soil mound surrounding a burrow entrance at Wind Cave National Park, South Dakota. As long as a burrow is inhabited, prairie dogs maintain the area around the entrance free from vegetation.

Pocket gophers in ecosystems: patterns and mechanisms

Abstract: Pocket gophers, despite their relatively small size, are an important element controlling ecosystem structure and development. Mielke (1977, p. 171) argues that "... Geomyidae provide a dynamic force to direct the biogeochemical attributes of the North American Prairie lands .... [T]he activities of fossorial rodents may provide an explanation for the genesis of North American Prairie soils," and Grinnell (1923, p. 148) asserts that "... our native plant life, on hill and mountainside, in canyon and mountain meadow, would soon begin to depreciate, were the gopher population completely destroyed." Effects on the productivity, heterogeneity, and trophic structure of ecosystems, occurring on various temporal and spatial scales, have been described for pocket gophers. Gophers influence the physical environment, altering patterns and rates of soil development and nutrient availability, microtopography, and the consequent abiotic environment. They affect the demography and abundance of plant species, changing vegetational patterning and diversity. They affect the behavior and abundance of other herbivores, from grasshoppers and ground squirrels to large grazers. In this article, we review the reThe activities of pocket gophers cascade through the trophic web

Moose, Microbes, and the Boreal ForestThrough selective browsing, moose change plant communities and ecosystem properties

Abstract: he ecology of moose is intimately tied to that of the boreal forest. Moose first appeared in the fossil record during the glacial advances of the late Pliocene and early Pleistocene, subsequently undergoing adaptive radiation that produced two genera (Cervalus and Alces) and at least four species (Telfer 1984). The sole extant species, Alces alces, radiated into eight subspecies, 6500-7000 years ago, of which seven survive (Telfer 1984). The current assemblage of aspen (Populus tremuloides), balsam poplar (Populus balsamifera), birch (Betula papyrifera), spruce (Picea glauca, Picea mariana), and balsam fir (Abies balsamea) that constitutes the boreal forest arose at about the same time (Larsen 1980). Both the boreal forest and moose

Plants Helping PlantsNew evidence indicates that beneficence is important in vegetation

Abstract: A lthough the importance of beneficial interactions as a factor of evolution was emphasized early in this century (Kropotkin 1902), the study of competition and predation have dominated ecology, and especially community ecology, during the last three decades (Strong et al. 1984). Recently, however, there has been a surge of interest in beneficial interactions between species (Boucher 1985, Vandermeer 1984), perhaps as a consequence of a waning faith in the importance of interspecific competition (Schoener 1982). Most of the obvious examples of beneficence (mutualism and commensalism) involve animal-animal, animal-fungus, plant-fungus, or plantanimal pairs. These interactions typically involve different trophic levels, and hence organisms that do not normally compete for resources. Plants living in close proximity commonly make demands on the same resources. Plants that benefit from their neighbors, therefore, are likely also to compete with them. That potential competitors may also benefit each other forms the basis of intercropping systems (Francis 1986), such as mixtures of clovers and sycamore seedlings (Haines et al. 1978) or of beans and corn (Boucher and Espinosa 1982).

Evolutionary Biology and Genetically Engineered CropsConsideration of evolutionary theory can aid in crop design

Abstract: M ost of the controversy surrounding the use of genetically engineered organisms has so far focused on unintended establishment of these organisms, or their genes, in enviroments where they could disrupt ecological systems or adversely affect human health (Gillett et al. 1985, Kolata 1985, Sharples 1982). In contrast, almost no attention has been devoted to potential, evolutionary responses of indigenous organisms to the genetically engineered organisms. These evolutionary changes could rapidly nullify the utility of the genetically engineered organisms and could significantly alter ecosystem function. In this article, I discuss how empirical and theoretical research in evolutionary biology could be used in the development of release strategies that may limit such problems without stifling the potential benefits of genetic engineering. I focus on the effects of planting genetically engineered crops containing genes that code for pest-resistance traits. Can we predict the evolutionary response of pest organisms to genetically engineered crops? Are there realistic tactics that could be used to minimize or beneficially manipulate the genetic responses of the pest organisms to genetically engineered crops? Although I restrict this discussion to pest-resistance genes in

Interplay between Physiology and Ecology in DigestionIntestinal nutrient transporters vary within and between species according to diet

Abstract: (JMD), who then described himself professionally as a physiologist, went for a bird walk with ecologists Martin Cody and the late Robert MacArthur. Near a stream they saw a Black Phoebe, a species of flycatcher confined to the vicinity of water. To MacArthur's question, "Why do you suppose the Black Phoebe lives only near water?", Diamond and Cody gave opposite dogmatic responses. Diamond insisted, "There must be physiological reasons, like low renal concentrating ability resulting in high water requirements. Physiological factors often determine an animal's ecology." Cody replied equally firmly, "Nonsense. Natural selection makes an animal's

Animal Influences on Ecosystem DynamicsLarge animals are more than passive components of ecological systems

Abstract: ited the grasslands and forests of North America, migratory birds filled the skies, and seemingly unlimited fishes and fur-bearing mammals populated the lakes and rivers. Early explorations by Jacques Cartier, Samuel de Champlain, Pierre Esprit Radisson, and Pierre Gaultier de Varennes revealed wildlife so abundant as to be almost unbelievable today (Bakeless 1950). It is clear from their descriptions, and those of Bates (1863) for the Amazon River basin and Bartram (1791), Hays (1871), and Morgan (1868) for North America, that animals had strong interactions with the ecosystems supporting them.

Comparative Conservation Biology of Oceanic Archipelagoes Hawaii and the Galdpagos

Abstract: Oceanic islands have had an important role in the history of evolutionary biology and are continuing to serve as crucial sites for evolutionary studies. The Hawai- ian Islands and the Galipagos Islands are two archipelagoes where much biological investigation has been, and continues to be, performed. Both ar- eas have also received attention be- cause of the vulnerability of their endemic animals and plants to dam- age by humans and organisms intro- duced by humans. The Hawaiian bio- ta has, in general, undergone much more destruction than that of the Galipagos. For example, whereas the Hawaiian archipelago has lost over 75% of its original endemic land bird fauna through prehistoric and histor- ic extinctions (Olson and James 1984, Scott et al., page 238-253 this issue), the Galipagos archipelago as a whole is not known to have lost a single land bird species. Oceanic islands are extremely vul- nerable to certain types of human- related biological invasions because of their long isolation from some of the selective forces that have shaped the evolution of continental orga- nisms. These forces include browsing and trampling by herbivorous mam- mals, predation by ants, virulent dis-

Environmental Degradation in the Pantanal EcosystemIn Brazil, the world's largest wetland is being threatened by human activities

Abstract: ment was part of the opening ceremonies of a worldwide campaign directed at the conservation of wetlands. The campaign was promoted by UNESCO, with the cooperation of the International Union for the Conservation of Nature and Natural Resources (IUCN) and the World Wildlife Fund (WWF). The Pantanal, with its extraordinary diversity and abundance of wildlife, is a threatened region. Deforestation; expanding agriculture; illegal hunting and fishing; and pollution of the water with herbicides, pesticides, and by-products of fuel alcohol production have caused a progressive deterioration of the natural environment, placing at risk one of Brazil's most important ecosystems.

The Conservation of Diversity in Forest Trees: Why and how should genes be conserved?

Abstract: eforestation, pollution, and climatic change threaten forest diversity all over the world. And because forests are the habitats for diverse organisms, the threat is extended to all the flora and fauna associated with forests, not only forest trees. In a worst case scenario, if the tropical forest in Latin America was reduced to the areas now set aside in parks and reserves, 66% of the world's plant species would go extinct, along with 69% of the birds and correspondingly high proportions of the other fauna (Myers 1984). But immediate loss of species is not the only danger. Among the surviving species, many populations will be lost, taking with them much of the genetic diversity upon which long-term survival and evolution depend. A really alarming thought is: What if the loss of biological diversity does irreversible damage to our planetary lifesupport system? At the root of this threat is human population growth. And to support our expanding population, we concentrate our agriculture on just a few species-20 species supply most of the world's food (US Committee on Genetic Vulnerability of Major Crops 1972). In these species, the genetic base is greatly reduced, both purposefully, to facilitate management, and by chance. This reduction leads to another problem of gene conservation: the The need is clear, but the task is enormous, and time is

Boundaries in the Protection of Nature Reserves: Translating multidisciplinary knowledge into practical conservation

Abstract: n most countries of the world, natural habitats are on the decline. To avoid indiscriminate land use and to allow evolutionary and ecological processes to function naturally, land has been set aside as national parks, reserves, forests, refuges, and recreation areas, which I refer to collectively as nature reserves. These nature reserves can serve as a baseline against which environmental change in adjacent areas can be measured. If, in addition, nature reserves are to protect biodiversity for the future, local human communities must be considered in nature reserve planning, design, and management (see Dasmann, page 487 this issue). Analyses of nature reserve protection should combine anthropocentric disciplines, such as economics, law, and anthropology, with the biological ones to reach a powerful multidisciplinary synthesis (Anadu 1987, Field and Johnson 1981, Forman and Godron 1986, Ives and Ives 1987, Janzen 1983, Myers 1987, Norton 1986, OTA 1986, Prims 1987, Sax and Keiter 1987, Risser 1985, Schonewald-Cox et al. 1983, Soule 1986, Usher 1986, Wilson 1988). There is a great gap between what has emerged from basic research and what nature reserve managers need for planning and evaluation of protection. Therefore, considerable attention is being given to translating the We can treat the

Intellectual Problems of Applied EcologyApplied problems can guide ecology just as clinical problems focus medical research

Abstract: here is no dirth of problems for applied ecologists. Red tides litter beaches with dead fish, greenhouse gases are changing the climate, habitats are being destroyed, and species are becoming extinct. Applied ecology studies organisms of practical importance and attempts to use the theoretical insights and empirical concerns of academic ecology in the solution of specific problems of environmental management. The diverse field of applied ecology includes such specialities as range management, fisheries science, and certain branches of environmental engineering. In addition to the obvious applications to improving human health and economic well-being, the influence of applied ecology extends tangibly into the spiritual and aesthetic realms. What constitutes an environmental problem depends in part on popular perception. An organism or habitat that has been incorporated into art, poetry, or national symbolism becomes the object of special concern. The California condor and the bald eagle have a special importance to the United States. The richer a country's history and literature the more complex the perception of problems of ecology. Conversely, national life is enriched by sensitivity to the local organisms. A people that has lost a sense of its own landscape is severely Ecology has deep-rooted characteristics that make its problems more difficult to solve than, for example, those of physics

Cooperative Foraging and Communication in CaterpillarsSilk and chemical markers may catalyze social evolution

Abstract: higher social insects, gregarious caterpillars have not advanced significantly from a primitive stage of communal grouping. Beginning with Wheeler (1923), biologists have considered the elements of true sociality (eusociality)-cooperative brood care, overlapping generations of parents and offspring, and division of labor-to be characteristic features of ants, termites, and some bees and wasps. Colonies of caterpillars clearly lack the first two of these criteria, and, while a less sophisticated, nonreproductive division of labor was reported to occur in some species of the tent caterpillars Malacosoma (Franz and Laux 1964, Wellington 1957), these findings have been challenged by recent work (Edgerly and Fitzgerald 1982, Papaj and Rausher 1983). In an early attempt to establish a paradigm for the evolution of coloniality in caterpillars, Balfour-Browne (1925) argued that gregarious cater-

Saving Endangered Species by TranslocationAre we tinkering with evolution

Abstract: species itself. Recent studies conducted in Hawaii of the Laysan finch (Telespyza cantans; Figure 1), endemic to Laysan Island, and a rock wallaby (Petrogale sp.; Figure 2) on the island of Oahu suggest that translocated populations may diverge very rapidly from parent populations. If this differentiation is genetically based, such translocations may represent human intervention in the evolutionary process, and wildlife managers need to consider this possibility when deciding whether to try translocation to save a threatened species. Recently Scott and Carpenter (1987) called attention to the fact that past attempts at reintroduction or translocation of a species have been poorly documented, leaving managers at a disadvantage in planning new programs. Translocations can have

Environmental impact of weed-control insects

Abstract: local and temporary. Such use of the organism is regulated under the legislation for chemical pesticides, and registration can be withdrawn if there are unwanted side effects. In contrast, classical biological control establishes an organism from another part of the world. With this approach the weed is continually controlled, but the introduction is generally irreversible. Once an organism is established, it is usually impossible to eradicate it. Most classical biological control organisms have been insects, although some micro-organisms, nematodes, and mites have been used. With a few exceptions, such as the White Amur fish, Ctenopharydon idella (Val.), vertebrates have not been used for weed control. Unless confined, their ecological impact tends to be devastating, such as the deforestation of the Mediterranean basin by goats. Worldwide, there are more than 300 examples in which an insect species has been introduced for the pur-

Floral AromaHow far will plants go to attract pollinators

Abstract: relationships between plants and insect pollinators challenge biologists ross-pollination is the transfer of pollen from anthers where it is produced to a flower stigma on a different plant. The value of cross-pollination is that it promotes gene mixing and results in greater vigor in the offspring. Because crosspollination is riskier than self-pollination, flowering plants have evolved many ways of ensuring its success. Plants that let the wind carry their pollen indiscriminantly to distant ovules must produce copious amounts of pollen to correct for inaccuracy of delivery. These plants, however, need produce only small, inconspicuous flowers. Other plants use biological agents to deliver their pollen, but at a cost of advertising for and paying the agents. Floral aroma is one example of flower advertisement, and in some cases may even act as compensation for pollination services. Wind-pollinated flowers may not emit aromas, nor may bird-pollinated flowers that rely on vivid red colors, which appear black to many insects (Faegri and van der Pijl 1979, Heinrich 1979b, von Frisch 1967). The origin and function of floral aroma have been of recent interest. The fossil record is incomplete but shows that plants with flowerlike structures and insects capable of evolving into pollinators began their radiations at about the same time

Comparing Australian Ecosystems to Those ElsewhereWhat is the significance of evolutionary history

Abstract: No one doubts that ecosystems are strongly influenced by their present-day physical context. Changes along environmental gradients are to be seen all around us. But how important is the long evolutionary history that shaped the biology of component species and led to those components assembling at a particular place? To tackle this question we must compare parts of the world that have similar present-day environments but different histories. Australia is a key laboratory for this natural experiment because much of its biota has had an evolutionary history separate from most other continents, and because it provides a wide range of environments. A variety of aspects of ecosystems have been compared between Australia (Figure 1) and elsewhere. An overview of these comparisons can ask which aspects of ecosystems depend on evolutionary history and which aspects are converAustralia is a key laboratory for this natural experiment

Biocultural restoration of a tropical forestArchitects of Costa Rica's emerging Guanacaste National Park plan to make it an integral part of local culture

Abstract: ne hot, windy day last summer, Daniel Janzen leaned in through the window of an open-air schoolhouse in northwestern Costa Rica and called to the teacher. The teacher left the blackboard, where he had been working a math problem. After chatting with the teacher for a few minutes in Spanish, Janzen handed him a photocopied note inviting the elementary school students to attend a speech by Costa Rican President Oscar Arias Sanchez in which Arias was to reaffirm conservation as one of the nation's top priorities. The speech would be given at nearby Santa Rosa National Park, where the class had already studied natural history as part of a new educational program. The invitation was delivered to several other elementary schools in the region, as well as to farmers, politicians, and other local residents.

Speciation in the Hawaiian DrosophilaSexual selection appears to play an important role

Abstract: large number of divergent forms from a primitive ancestor. By far the most outstanding of these examples is the Hawaiian Drosophilidae (see reviews in Carson et al. 1970, Carson and Kaneshiro 1976, Hardy and Kaneshiro 1981, Kaneshiro 1983). Here, in this isolated group of Pacific Basin islands situated more than 3500 kilometers from the nearest land mass, are found nearly onefourth of the known species in the family Drosophilidae. More than 95% (484 out of 509 species in two genera) are endemic to Hawaii; they are found nowhere else in the world. Considering Hawaii's small land mass-approximately 15,500 square kilometers-and the geological newness of the present-day high islands of the Hawaiian Archipelago, the Hawaiian Drosophilidae represents one of the most striking examples of adaptive radiation known for any group of animals anywhere, and these islands offer a unique opportunity for investigating dynamic stages of evoluWith their often bizarre