Assessment of soil calcium status in red spruce forests in the northeastern United States

Long-term changes in concentrations of available Ca in soils of redspruce forests have been documented, but remaining questions aboutthe magnitude and regional extent of these changes have precluded anassessment of the current and future status of soil Ca. To addressthis problem, soil samples were collected in 1992—93from 12 sites in New York, Vermont, New Hampshire, and Maine toprovide additional data necessary to synthesize all availableresearch results on soil Ca in red spruce forests. Sites werechosen to encompass the range of environmental conditionsexperienced by red spruce. Concentrations of exchangeableCa ranged from 2.13 to 21.6 cmol_ckg^–1 in the Oa horizon, and from 0.11 to 0.68cmol_c kg^–1 in the upper 10 cm of theB horizon. These measurements expanded the range of exchangeable Ca reported in the literature for both horizons in northeastern redspruce forests. Exchangeable Ca was the largest Ca fraction in theforest floor at most sites (92% ofacid-extractableCa), but mineral Ca was the largest fraction at the three sites that also had the highest mineral-matter concentrations. Theprimary factor causing variability in Ca concentrations among siteswas the mineralogy of parent material, but exchangeable concentrationsin the B horizon of all sites were probably reduced by acidicdeposition. Because the majority of Ca in the forest floor isin a readily leachable form, and Ca inputs to the forest floor from the mineral soil and atmospheric deposition have beendecreasing in recent decades, the previously documented decreasesin Ca concentrations in the forest floor over previous decades mayextend into the future.     

Chemosensory Adaptation to Lysozyme and GTP Involves Independently Regulated Receptors in Tetrahymena thermophila

ABSTRACT. Chemosensory adaptation is seen in Tetrahymena thermophila following prolonged exposure (ten minutes) to micromolar concentrations of the chemorepellents lysozyme or guanosine triphosphate (GTP). Since these cells initially show repeated backward swimming episodes (avoidance reactions) in these repellents, behavioral adaptation is seen as a decrease in this repellent-induced behavior. The time course of this behavioral adaptation is paralleled by decreases in the extents of surface binding of either [³²P]GTP or [³H]lysozyme in vivo. Scatchard plot analyses of repellent binding in adapted cells suggests the behavioral adaptation is due to a dramatic decrease in the number of surface binding sites, as represented by decreased Bmax values. The estimated K_D values for nonadapted cells are 6.6 μM and 8.4 μM for lysozyme and GTP binding, respectively. Behavioral adaptation and decreased surface receptor binding are specific for each repellent. The GTP adapted cells (20 μM for ten minutes) still respond behaviorally to 50 μM lysozyme and bind [³H]lysozyme normally. Lysozyme adapted cells (50 μM for ten minutes) still bind [³²P]GTP and respond behaviorally to GTP. All the behavioral and binding changes seen are also reversible (deadaptation). Neomycin was shown to be a competitive inhibitor of [³H]lysozyme binding and lysozyme-induced avoidance reactions, but it had no effect on either [³²P]GTP binding or GTP-induced or avoidance reactions. These results are consistent with the hypothesis that there are two separate repellent receptors, one for GTP and the other for lysozyme, that are independently downregulated during adaptation to cause specific receptor desensitization and consequent behavioral adaptation.     

Egg maturation strategy and survival trade-offs in holometabolous insects: a comparative approach

One of the key predictions of general life-history theory is that reproduction incurs a survival cost. Although there is a convincing body of evidence to support this prediction at the intraspecific level in insects, evidence at the interspecific level is relatively scarce, as is the case for other animals. By employing two methods of phylogenetically controlled analysis, we demonstrate the existence of a negative correlation between life-span and early life investment in reproduction, across a wide diversity of Lepidoptera. The measure of initial reproductive effort used was the 'ovigeny index', defined as the proportion of the lifetime potential egg complement that is mature (ready to lay) upon female emergence. We present a graphical model for holometabolous insects, illustrating the trade-offs that are hypothesized to occur among capital resources (soma vs non-soma and initial eggs vs storage) in relation to variation in ovigeny index. These trade-offs, for which there is some empirical support, are postulated to underlie the life-span/ovigeny index relationship observed in the Lepidoptera and also in other insect orders.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 293–302.     

Colony characteristics influence the risk of nest predation of a polydomous ant by a monotreme

Although predation of individual social insect workers has little effect on colony fitness, nest predation may be a significant selective agent because it can result in substantial loss of reproductive success. Surprisingly, the consequences of predation on social insect nests are poorly understood. In the present study, we investigate the factors that correlate with the probability of predation by echidnas, Tachyglossus aculeatus , on nests and colonies of the facultatively polydomous meat ant, Iridomyrmex purpureus. In particular, we investigate whether colony fragmentation provides a mechanism for reducing the costs of echidna predation. Over 2 years, 138 of the 140 colonies on our study site were depredated. Nest predation was most common in woodlands but with no obvious seasonal patterns. The probability of nest predation was positively correlated with the size of the nest, and negatively correlated with the density of surrounding nests. Although polydomous colonies are at a similar risk of predation by echidnas, the proportion of depredated nests is negatively correlated with the number of nests; thus, the probability that one or more nests avoid predation is increased with increasing nest numbers. Surprisingly, we found no influence of the level of echidna predation on colony growth, measured by either changes in the number of nests or the number of nest entrance holes.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 1–8.     

Kinship, Contract, Community, and State: Anthropological Perspectives on China

Kinship, Contract, Community, and State: Anthropological Perspectives on China. Myron L. Cohen. Stanford: Stanford University Press, 2005. 359 pp.