Forest ecologists and biogeochemists have used a variety of extraction techniques to assess labile vs. non-labile soil P pools in chronosequences, the balance between biological vs. geochemical control of P transformations across a wide range of soil orders, the role of plants with either N-fixing or mycorrhizal symbionts in controlling soil P fractions, and to make inferences about plant-available P. Currently, variants of the sequential extraction procedure developed by M. J. Hedley and co-workers afford the greatest discrimination among labile and non-labile organic and inorganic P pools. Results of recent studies that used this technique to evaluate P fractions in forest soils indicate the following: (1) in intact, highly weathered forest soils of the humid tropics, Hedley-labile P values are several times larger than extractable P values resulting from mildly acidic extracting solutions which were commonly used in the past 2 decades; (2) pools of Hedley-labile P are several times larger than the annual forest P requirement and P required from the soil annually in both temperate and tropical forests; (3) long-term trends in non-labile P pools during pedogenesis are adequately represented by the Walker and Syers' model of changes in P fractionation during soil development. However, to better represent trends in pools that can supply plant-available P across forest soils of different age and weathering status, the paradigm should be modified; and (4) across a wide range of tropical and temperate forest soils, organic matter content is an important determinant of Hedley-labile P.

Isolated theropod teeth are common Mesozoic fossils and would be an important data source for paleoecology biogeography if they could be reliably identified as having come from particular taxa. However, obtaining identifications is confounded by a paucity of easily identifiable characters. Here we discuss a quantitative methodology designed to provide defensible identifications of isolated teeth using Tyrannosaurus as a comparison taxon. We created a standard data set based as much as possible on teeth of known taxonomic affinity against which to compare isolated crowns. Tooth morphology was described using measured variables describing crown length, base length and width, and derived variables related to basal shape, squatness, mesial curve shape, apex location with respect to base, and denticle size. Crown curves were described by fitting the power function Y ϭ a ϩ bX 0.5 to coordinate data collected from lateral-view images of mesial curve profiles. The b value from these analyses provides a measure of curvature. Discriminant analyses compared isolated teeth of various taxonomic affinities against the standard. The analyses classified known Tyrannosaurus teeth with Tyrannosaurus and separated most teeth known not to be Tyrannosaurus from Tyrannosaurus. They had trouble correctly classifying teeth that were very similar to Tyrannosaurus and for which there were few data in the standard. However, the results indicate that expanding the standard should facilitate the identification of numerous types of isolated theropod teeth. 2005 Wiley-Liss, Inc. © 2005 Wiley-Liss, Inc. Key words: dinosauria; theropoda; teeth; morphometrics; taxonomy; discriminant analysisOne of the first steps in studying interactions among ancient organisms and their environments is identifying the taxa that comprised the ecosystem. Regrettably, this task can be quite complicated. For vertebrates, the difficulties in obtaining taxonomic identifications for isolated bones, and in some cases partial skeletons, have plagued researchers since the infancy of paleontology. The difficulties stem from a lack of recognized characters in many elements, degradation and loss of anatomical data through taphonomic processes, and the fact that withintaxon variation is poorly understood for most bones of most taxa. These issues confound study into most questions regarding ancient vertebrates, but the situation is acute where bone beds or attempts to generate paleopopulation census data are concerned (e.g., Dodson, 1971;

Nitrogen acquisition is a major challenge for herbivorous animals, and the repeated origins of herbivory across the ants have raised expectations that nutritional symbionts have shaped their diversification. Direct evidence for N provisioning by internally housed symbionts is rare in animals; among the ants, it has been documented for just one lineage. In this study we dissect functional contributions by bacteria from a conserved, multi-partite gut symbiosis in herbivorous Cephalotes ants through in vivo experiments, metagenomics, and in vitro assays. Gut bacteria recycle urea, and likely uric acid, using recycled N to synthesize essential amino acids that are acquired by hosts in substantial quantities. Specialized core symbionts of 17 studied Cephalotes species encode the pathways directing these activities, and several recycle N in vitro. These findings point to a highly efficient N economy, and a nutritional mutualism preserved for millions of years through the derived behaviors and gut anatomy of Cephalotes ants.

Op as a proxy for gs or E under low E conditions. Further, we show that incorporation of a multi-species L-E scaling into the leaf water model has the potential to both improve the prediction accuracy and simplify parameterization of the model when compared with the conventional approach. This has important implications for future modelling of oxygen isotope ratios.

No abstract

Growth series of femora, tibiotarsi, and humeri of the Canada goose Branta canadensis were examined to evaluate whether bone surface textures are reliable indicators of relative age and skeletal maturity in this taxon. The relationship between surface texture and skeletal maturity was analysed by comparing element texture types with both size-based and size-independent maturity estimates. A subsample of hindlimb elements was thin sectioned to observe histological structures underlying various surface textures. Three relative age classes of elements are identifiable based on surface texture. Juvenile and subadult bone textures have fibrous and/or porous areas on the bone shaft and are distinguished by the presence (in juveniles) or absence (in subadults) of coarse longitudinal striations in proximal and/or distal regions. Adult bone texture lacks surface porosity. Immature textures are caused by channels in fibrolamellar bone intersecting the bone surface; the presence or absence of striations is determined by channel orientation. Mature textures may be underlain by fibrolamellar bone with little to no surface exposure of channels, or by lamellar bone deposited after rapid growth ceases. The utility of the textural ageing method appears intimately related to the uninterrupted determinate growth regime of Branta . This suggests that bone surface textures may prove useful as skeletal maturity indicators in both modern and fossil taxa with similar growth regimes, but may not necessarily be reliable for taxa with interrupted and/or indeterminate growth.

Growth series of femora, tibiae, and humeri of the American alligator Alligator mississippiensis were examined to assess the relationship between bone surface textures and relative skeletal maturity. Element texture types were compared with both size‐based and size‐independent maturity estimates. Selected elements were thin sectioned to observe the histological structures underlying various surface textures. Results suggest little to no relationship between bone textures and skeletal maturity in Alligator. Controlling for additional factors suspected to affect textural variation – sexual dimorphism, seasonally interrupted growth, wild vs. captive habitat, and geographical range – provides little resolution. Indeterminate growth is almost certainly a factor; however, this alone cannot explain all observed variability. Histological analyses reveal that highly porous surface textures are often associated with zones composed of fibrolamellar bone; smoother textures are generally underlain by lamellar zones or annuli. Textures of intermediate porosity may be associated with more than one histological pattern. Until the factors affecting bone texture changes in modern crocodylians are better understood, it is recommended that the textural ageing method be applied with caution to studies of fossil archosaurs with crocodylian‐like or unknown growth regimes. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 150, 1–39.

We present an objective and quantitative technique to reconstruct former sea level from assemblages of salt-marsh foraminifera using partitioning around medoids (PAM) cluster analysis and linear discriminant functions. Three salt marshes, representing different physiographic environments in southern New Jersey, were selected for describing the modern distribution of foraminifera from 56 surface samples. PAM estimated the number and composition of assemblages present at each site and showed that foraminifera adhered to the concept of elevation-dependent ecological zones, making them appropriate sea-level indicators.This approach has several advantages in comparison to hierarchical clustering. Application of PAM to a regional dataset generated by combining all samples identified the presence of five distinctive biozones occupying defined elevation ranges. The characteristics of these biozones were similar to those identified elsewhere on the mid-Atlantic coast of the USA. Classification of each of the 56 samples as belonging to one of the five biozones enabled us to develop linear discriminant functions, which confirmed their distinctiveness. These functions can estimate the probability that assemblages of foraminifera preserved in samples of salt-marsh sediment represent one of the five modern biozones. Recognition of these biozones in sequences of salt-marsh sediment provides a means to reconstruct sea level. We collected a 4.0 m core from Leeds Point, New Jersey to investigate the practical application of this approach to reconstructing former sea level. The linear discriminant functions were used to indicate the faunal origin of 32 core samples and in cross validation tests were accurate in 54 of 56 cases.The approach described can be used as an independent means to reconstruct sea level or to check the ecological plausibility of results from other techniques including transfer functions.