Amphibians as metrics of critical biological thresholds in forested headwater streams of the Pacific Northwest, U.S.A.

1. Amphibians are recognized both for their sensitivity to environmental perturbations and for their usefulness as cost-effective biometrics of ecosystem integrity (=system health).
2. Twenty-three years of research in headwater streams in the Klamath-Siskiyou and North Coast Bioregions of the Pacific Northwest, U.S.A., showed distinct patterns in the distribution of amphibians to variations in water temperature, % fine sediments and the amount of large woody debris (LWD).
3. Here, we review seven studies that demonstrate connections between species presence and abundance and these three in-stream variables. These data were then used to calculate realized niches for three species, the southern torrent salamander, the larval coastal tailed frog and the larval coastal giant salamander, relative to two of these environmental stressors (water temperature and % fine sediments). Moreover, multivariate generalized additive models were used to predict the presence of these three amphibians when these three stressors act in concert.
4. Stream-dwelling amphibians are shown to be extremely sensitive to changes in water temperature, amounts of fine sediment and LWD, and specific thresholds and ranges for a spectrum of animal responses can be used to manage for headwater tributary ecosystem integrity.
5. Consequently, amphibians can provide a direct metric of stream ecosystem integrity acting as surrogates for the ability of a stream network to support other stream-associated biota, such as salmonids, and their related ecological services.     

Special Section on Canada Lynx-Habitat Relations in the Contiguous United States

Abstract The southern extent of the range of Canada lynx (Lynx canadensis) extends into the contiguous United States in locations from Washington State in the West to northern Maine in the East. Lynx persist in various habitats across this range from high-elevation wilderness to intensively managed industrial forests. Lynx habitat use at the species' southern range boundary was poorly understood before the species was listed as Threatened under the Endangered Species Act in 2000, because most research had been conducted in boreal forest. The papers in this special section outline a variety of questions regarding lynx populations at the southern extent of their range, address topics on lynx space use and denning habitat, and provide generally consistent results in terms of features important to lynx habitat use despite the wide variation in specific habitats among the study areas.     

Behavioural responses of fathead minnows to hypoxanthine-3-N-oxide at varying concentrations

Antipredator behaviour of fathead minnows Pimephales promelas increased significantly on exposure to hypoxanthine-3-N-oxide at concentrations as low as 0·4 n with no further increase in response at concentrations up to 6·7.     

A molecular perspective on the evolution of microteiid lizards (Squamata, Gymnophthalmidae), and a new classification for the family

A molecular phylogeny was reconstructed for 26 recognized genera of the Gymnophthalmidae using a total of 2379 bp of mitochondrial (12S, 16S and ND4) and nuclear (18S and c-mos) DNA sequences. We performed maximum parsimony (MP) and maximum likelihood (ML) analyses, and data partitions were analysed separately and in combination under MP. ML analyses were carried out only on the combined sequences for computational simplicity. Robustness for the recovered nodes was assessed with bootstrap and partitioned Bremer support (PBS) analyses. The total molecular evidence provided a better-resolved hypothesis than did separate analysis of individual partitions, and the PBS analysis indicates congruence among independent partitions for support of some internal nodes. Based on this hypothesis, a new classification for the family is proposed. Alopoglossus , the sister group of all the other Gymnophthalmidae was allocated to a new subfamily Alopoglossinae, and Rhachisaurus (a new genus for Anotosaura brachylepis) to the new Rhachisaurinae. Two tribes are recognized within the subfamily Gymnophthalminae: Heterodactylini and Gymnophthalmini, and two others within Cercosaurinae (Ecpleopini and Cercosaurini). Some ecological and evolutionary implications of the phylogenetic hypothesis are considered, including the independent occurrence of limb reduction, body elongation, and other characters associated with fossoriality.     

The Properties of an Enzyme System Degrading Endogenous Phospholipids of Tetrahymena pyriformis

SYNOPSIS. Tetrahymena pyriformis contains a potent system of lipolytic enzymes which is activated by disruption of the cells. The extent to which endogenous lipids of the homogenate are degraded depends upon the age of the culture and the strain of T. pyriformis used. In their most active form, the enzymes can hydrolyze nearly 60% of the endogenous phospholipids within one hour at room temperature. The products of this reaction are probably responsible for the frequently reported instability of Tetrahymena enzyme systems in vitro. The use of inhibitors and the careful choice of culture conditions can reduce lipid degradation to a negligible level.     

An Introduction to Phylogenetically Based Statistical Methods, with a New Method for Confidence Intervals on Ancestral Values

Interspecific comparisons have played a prominent role in evolutionarybiology at least since the time of Charles Darwin. Since 1985,the "comparative method" has been revitalized by new analyticaltechniques that use phylogenetic information and by increasedavailability of phytogenies (often from molecular data sets).Because species descend from common ancestors in a hierarchicalfashion, related species tend to resemble each other (elephantslook like elephants); therefore, cross-species data sets generallydo not comprise independent and identically distributed datapoints. Phylogenetically based statistical methods attempt toaccount for this fact. Phylogenetic methods allow traditionaltopics in comparative and ecological physiology to be addressedwith greater rigor, including the form of allometric relationshipsand whether physiological phenotypes vary predictably in relationto behavior, ecology or environmental characteristics, whichprovides evidence about adaptation. They can also address newtopics, such as whether rates of physiological evolution havediffered among lineages (clades), and where and when a phenotypefirst evolved. We present brief overviews of three phylogeneticallybased statistical methods: phylogenetically independent contrasts,Monte Carlo computer simulations to obtain null distributionsof test statistics, and phylogenetic autocorrelation. In a newresult, we show analytically how to use independent contraststo estimate ancestral values and confidence intervals aboutthem. These confidence intervals often exceed the range of variationobserved among extant species, which points out the relativelygreat uncertainty inherent in such inferences. The use of phytogeniesshould become as common as the use of body size and scalingrelationships in the analysis of physiological diversity.     

Other Perspectives on the Kennewick Man Controversy

Skull Wars: Kennewick Man, Archaeology, and the Battle for Identity. David Hurst Thomas. New York: Basic Books, 2000. 326 pp.
Riddle of the Bones: Politics, Science, Race, and the Story of Kennewick Man. Roger Downey. New York: Copernicus, 2000. 202 pp.