Social synchronization of circadian rhythms of metabolism in honeybees (Apis mellifera)

ABSTRACT. Groups of honeybee workers ( Apis mellifera Linn.; Hymenoptera: Apidae) show endogenous circadian rhythms in metabolic activity. Workers entrained to two different photoperiods, when put together in a group, coordinate their individual metabolic activity cycles into a synchronized group oscillation. Either physical interaction among workers, or a low volatility contact pheromone, is implicated in the control of this oscillating system.     

Galactose-induced Ethylene Evolution in Mung Bean Hypocotyls: A Possible Mechanism for Galactose Retardation of Plant Growth

Galactose has long been known to inhibit growth in certain plant systems and more recently to promote abscission. These same systems are similarly affected by ethylene. The mung bean (Phaseolus aureus Roxb.) hypocotyl system was employed to ascertain whether the inhibitory effects of galactose might be regulated through ethylene. Galactose alone (at 10 and 100 mM) of the many carbohydrates tested elicited high rates of ethylene evolution (1.5–4.0 nl/g fresh weight x h) as determined by gas chroma-tography. Hook opening, pigment formation, and hypocotyl elongation were inhibited by this resultant ethylene. Galactose and auxin were found to act synergistically with respect to ethylene induction. Use of an auxin antagonist and auxin transport inhibitor revealed that galactose-induced ethylene formation is auxin dependent. Time course studies indicate that this effect may be auxin-sparing. Methionine appears to be the substrate of galactose-induced ethylene. since a methionine antagonist [L-2-amino-4-(2′-amino ethoxy)-trans-3-butenoic acid] abolished the induction. Potential interrelationships between galactose and ethylene synthesis are discussed.     

The annual cycle of wing-moult and breeding in the Wattled Starling Creatophora cinerea

Moult, breeding and seasonal occurrence of the Wattled Starling Creatophora cinerea throughout its range in Africa are reviewed based on data from museum specimens and the published literature. Neither moult nor breeding follows a rigid seasonal pattern, although there are some regional differences, and overlap between moult and breeding is unlikely. The regular occurrence of interrupted wing-moult may be associated with nomadic movements rather than opportunistic breeding.     

Vulnerability and Place: Flat Land and Uneven Risk in New Orleans

Vulnerability to extreme events is shaped by both physical and social factors, and Hurricane Katrina brutally exposed that fact in New Orleans. Historically, low-income Irish and Italian populations suffered when floods washed over the Crescent City. Modifications in the structural defenses to floods and shifting demographics since 1950 altered the geography of vulnerability. In recent years, both blacks and whites have occupied below-sea-level sites, exposing both to flood risks, although the racial composition of the city has undergone a near reversal. Additionally, low-income residents, found disproportionately within the African American population, suffered dual vulnerability. Not only did many live in low-lying areas but evacuation plans relied on private automobiles that left many poor residents to endure the impact of the hurricane-induced flooding.     

Empirical geographic modeling of switchgrass yields in the United States

Switchgrass (Panicum virgatum L.) is a perennial grass native to the United States that has been studied as a sustainable source of biomass fuel. Although many field‐scale studies have examined the potential of this grass as a bioenergy crop, these studies have not been integrated. In this study, we present an empirical model for switchgrass yield and use this model to predict yield for the conterminous United States. We added environmental covariates to assembled yield data from field trials based on geographic location. We developed empirical models based on these data. The resulting empirical models, which account for spatial autocorrelation in the field data, provide the ability to estimate yield from factors associated with climate, soils, and management for both lowland and upland varieties of switchgrass. Yields of both ecotypes showed quadratic responses to temperature, increased with precipitation and minimum winter temperature, and decreased with stand age. Only the upland ecotype showed a positive response to our index of soil wetness and only the lowland ecotype showed a positive response to fertilizer. We view this empirical modeling effort, not as an alternative to mechanistic plant‐growth modeling, but rather as a first step in the process of functional validation that will compare patterns produced by the models with those found in data. For the upland variety, the correlation between measured yields and yields predicted by empirical models was 0.62 for the training subset and 0.58 for the test subset. For the lowland variety, the correlation was 0.46 for the training subset and 0.19 for the test subset. Because considerable variation in yield remains unexplained, it will be important in the future to characterize spatial and local sources of uncertainty associated with empirical yield estimates.     

Behavioural strategies of cormorants (Phalacrocoracidae) foraging under challenging light conditions

Diving is indicative of foraging in cormorants (Phalacrocoracidae). We have investigated a range of parameters associated with diving in Great Cormorants Phalacrocorax carbo to provide insight into the bases of cormorant predatory strategies. We hypothesize that if vision is important in cormorant foraging behaviour, and if they are not constrained by the position of their prey in the water column, then diving behaviour will be modulated primarily in response to the diel variation in ambient light levels. Specifically, we propose that cormorants forage at shallower depths when light levels are low, and more deeply when light levels are high. We provide evidence that this is the case. We recorded the occurrence of cormorant diving behaviour using implanted data loggers and recorded ambient light levels and water temperature using leg-mounted loggers in a sample of free-living Great Cormorants in Greenland. Our results show that dives are shallower at the beginning and end of each day when light levels are lower. We suggest that these data support the hypothesis that cormorant foraging is visually-guided even though recent evidence has shown that their underwater visual acuity is poor.     

Validation of a Demographic Model for Woodland Caribou

Abstract: Wildlife population models are potentially valuable for conservation planning. Validation is necessary to ensure that models are sufficiently robust for predicting management outcomes consistent with conservation objectives. Sorensen et al. (2008) produced a model of woodland caribou (Rangifer tarandus) population growth rate that was recently modified and used as a predictive tool at several scales. We computed confidence intervals and evaluated the performance of this model using novel data. Confidence intervals were wide, and results suggested that the model may have a positive bias, resulting in over-estimation of population growth rates, as well as low predictive power. Wide confidence intervals mean that current understanding of factors governing woodland caribou herd dynamics is not sufficient for wildlife managers to make reliable projections of responses to management.