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In evolutionary time, species come and go. In ecological time—anything from days to decades or even centuries—most species, in most places, persist. They do so in complex networks of local communities and extended metacommunities, within and between which even similar and closely related species may vary greatly in abundance. And while processes such as invasion and succession sometimes bring about a rapid reordering of the biological status quo for a particular site or region, species more typically maintain themselves in fairly constant numbers, neither taking over everything, like kudzu, nor dwindling to nothing, like the dodo.
The glaciers in the Blackfoot–Jackson Glacier Basin of Glacier National Park, Montana, decreased in area from 21.6 square kilometers (km2) in 1850 to 7.4 km2 in 1979. Over this same period global temperatures increased by 0.45°C (± 0.15°C). We analyzed the climatic causes and ecological consequences of glacier retreat by creating spatially explicit models of the creation and ablation of glaciers and of the response of vegetation to climate change. We determined the melt rate and spatial distribution of glaciers under two possible future climate scenarios, one based on carbon dioxide–induced global warming and the other on a linear temperature extrapolation. Under the former scenario, all glaciers in the basin will disappear by the year 2030, despite predicted increases in precipitation; under the latter, melting is slower. Using a second model, we analyzed vegetation responses to variations in soil moisture and increasing temperature in a complex alpine landscape and predicted where plant communities are likely to be located as conditions change.
Most community-based models in ecology assume that all individuals within a species respond similarly to environmental conditions and thereby exert identical effects as consumers or prey. Rather, individuals differ among systems, with important implications for population demographics and community interactions. For widely distributed assemblages made up of poikilotherms with high first-year mortality, species-specific differences in growth reaction norms as affected by both temperature and genotype will influence biotic interactions. For a broadly distributed fish assemblage, first-year growth does not vary with latitude for a planktivorous prey species, but declines with increasing latitude for a terminal piscivore. Size-based competitive interactions between these species are likely to be more intense at high latitudes, as they spend an extended time sharing resources during early life. Such patterns probably are pervasive and must be considered when seeking to understand species interactions. Improving our knowledge of how temperature and local adaptations affect size-based interactions should enhance our ability to manage and conserve widespread assemblages.
Speciation, the set of processes by which two populations of one species become distinct species, is an important topic in evolutionary biology. It is usually impractical to conduct experiments on how new species form, but occasionally the natural history of a species places it in a context that may be thought of as a “natural experiment” with regard to speciation. One such natural experiment involves the periodical cicadas of eastern North America, a group in which populations have become isolated in time and space. Some of these isolated populations appear to have evolved into distinct genetic lineages. A rare life-cycle switching event brought two such lineages into contact in the relatively recent past, and the two lineages are now behaving as distinct species. This natural experiment provides important insights into species differences and the processes that underlie species formation.
In situ, on-farm conservation is an important complement to ex situ conservation of traditional crop varieties. In Yunnan Province, China, management for crop diversity by mixed planting (intercropping) of traditional and hybrid rice varieties provides a possible means for sustainable on-farm conservation of traditional rice varieties. Since the adoption of this form of crop diversity management in 1997, the number of traditional rice varieties in cultivation has increased dramatically and now includes some varieties that were formerly locally extinct. The cultivated area of traditional varieties has also been greatly expanded. This form of management is easy to implement and links farmers' economic concerns with conservation. Management for crop diversity can promote on-farm conservation of rice, and potentially other crops too, in a feasible and sustainable way.
Evolutionary indeterminists argue that, in addition to any indeterminism introduced by quantum events, at least some evolutionary processes are themselves fundamentally indeterministic. That is, they maintain that the chance element in evolutionary processes results from indeterminism in the processes themselves, rather than simply from our cognitive limitations. Not everyone has been persuaded. A number of philosophers have argued that claims for evolutionary indeterminism are premature at best and deeply confused at worst. They maintain that evolutionary processes can and should be understood as deterministic processes. According to them, “chance” is merely a word denoting our ignorance of causes. This controversy is now one of the liveliest topics in the philosophy of biology. This article reviews the main arguments on each side, showing how the issues at stake in this debate raise fundamental questions about the nature of science as an explanatory enterprise and of the world it seeks to explain.
In this article we report on a regional study in the Pacific Northwest concerning the attitudes of scientists, resource managers, representatives of interest groups, and members of the involved public regarding preferred roles for research and field ecologists in natural resource management. Specifically, we examine the question of whether scientists should act as policy advocates and, if so, in what way. We also examine the factors that are perceived to affect scientists' credibility in these roles.