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Human activities dramatically change the abundance, diversity, and composition of species. However, little is known about how the most intense human activity, urbanization, alters food webs and trophic structure in biological communities. Studies of the Phoenix area, situated amid the Sonoran Desert, reveal some surprising alterations in the control of trophic dynamics. Species composition is radically altered, and resource subsidies increase and stabilize productivity. Changes in productivity dampen seasonal and yearly fluctuations in species diversity, elevate abundances, and alter feeding behaviors of some key urban species. In urban systems—in contrast to the trophic systems in outlying deserts, which are dominated by limiting resources—predation by birds becomes the dominant force controlling arthropods on plants. Reduced predation risk elevates the abundance of urban birds and alters their foraging behavior such that they exert increased top-down effects on arthropods. Shifts in control of food web dynamics are probably common in urban ecosystems, and are influenced by complex human social processes and feedbacks.
Decomposition in the Arctic has been slower than plant growth, causing an accumulation of detritus in tundra soils. Climate warming may result in carbon (C) loss by accelerating the decomposition of soil organic matter (SOM). Nitrogen (N) release from SOM may also enhance plant growth, which is limited by N availability in tundra ecosystems. Since N acquisition varies by plant species, changes in plant community composition resulting from climate change may alter carbon cycling in tundra soils. Shrubs are growing in predominance in tundra communities in response to warming. Since they are the woodiest plants in the tundra, this may increase ecosystem C storage, because wood has the highest C:N ratio of any plant tissue and decomposes slowly. Whether net ecosystem C storage increases or decreases will depend on the balance of (a) C losses from SOM and (b) C storage in plant pools due to higher primary productivity and changes in plant community composition.
We call into question the idea that birds have not evolved unique physiological adaptations to desert environments. The rate at which desert larks metabolize energy is lower than in mesic species within the same family, and this lower rate of living translates into a lower overall energy requirement in the wild. We argue that selection has reduced oxygen consumption at the tissue level under basal conditions for birds living in deserts. We document that total evaporative water loss—the sum of cutaneous water loss (CWL) and respiratory water loss—is reduced in desert birds, and present evidence that changes in CWL are responsible for this pattern. The diminution in CWL is attributable to changes in the lipid structure of the stratum corneum of the skin, the physical barrier to diffusion of water vapor. Finally, we show linkages between physiology and life-history attributes of larks along an aridity gradient; birds from deserts have not only a reduced rate of metabolism but also a small clutch size and slow nestling development. Hence, attributes of physiology are correlated with traits that directly affect reproductive success. Our hope is that we will prompt students to question the notion that birds do not possess physiological adaptations to the desert environment, and raise the specter of doubt about “preadaptation” in birds living in deserts.
The farming of salmon and other marine finfish in open net pens continues to increase along the world's coastlines as the aquaculture industry expands to meet human demand. Farm fish are known to escape from pens in all salmon aquaculture areas. Their escape into the wild can result in interbreeding and competition with wild salmon and can facilitate the spread of pathogens, thereby placing more pressure on already dwindling wild populations. Here we assess the ecological, genetic, and socioeconomic impacts of farm salmon escapes, using a risk-assessment framework. We show that risks of damage to wild salmon populations, ecosystems, and society are large when salmon are farmed in their native range, when large numbers of salmon are farmed relative to the size of wild populations, and when exotic pathogens are introduced. We then evaluate the policy and management options for reducing risks and discuss the implications for farming other types of marine finfish.
We examined the effects of different types of collaboration on the citation rates of 837 research papers published in Oecologia from 1998 through 2000. Multiauthored papers had higher annual citation rates, but also higher self-citation rates, than single-authored papers. Interdisciplinary collaboration between institutions increased citation rates, whereas in-house collaboration reduced them. Contrary to our predictions, international collaboration had no effect on the citation rates of ecological papers, and US ecologists benefited from collaboration more than their European colleagues. Altogether, our results indicate that scientific collaboration in ecology has a rather minor effect on the impact of the resulting publications, as measured by their citation rates.
I surveyed chapters on animal behavior in 11 introductory textbooks to see how well textbooks introduce current research in the field. Chapters on animal behavior were placed in or near the sections on ecology and often near sections on animals. Within chapters, the introductory textbooks tended to present the same topics in a standard sequence. This sequence generally agrees with the sequence of chapters in an advanced textbook. Textbooks showed little consistency, however, in the terms they presented in boldface type. Different textbooks presented different terms in boldface type, so most “essential terms” were featured in only one textbook. Terms in boldface from introductory textbooks were not often used in an advanced textbook or research articles in animal behavior. Textbooks rarely showed alternative hypotheses or data from control groups when presenting animal behavior. Textbooks seem to present an abundance of unnecessary terms and miss the opportunity to illustrate the process of science using observations of animals.