Quantifying the impact of current and future tropospheric ozone on tree biomass, growth, physiology and biochemistry: a quantitative meta-analysis

The northern hemisphere temperate and boreal forests currently provide an important carbon sink; however, current tropospheric ozone concentrations ([O₃]) and [O₃] projected for later this century are damaging to trees and have the potential to reduce the carbon sink strength of these forests. This meta‐analysis estimated the magnitude of the impacts of current [O₃] and future [O₃] on the biomass, growth, physiology and biochemistry of trees representative of northern hemisphere forests. Current ambient [O₃] (40 ppb on average) significantly reduced the total biomass of trees by 7% compared with trees grown in charcoal‐filtered (CF) controls, which approximate preindustrial [O₃]. Above‐ and belowground productivity were equally affected by ambient [O₃] in these studies. Elevated [O₃] of 64 ppb reduced total biomass by 11% compared with trees grown at ambient [O₃] while elevated [O₃] of 97 ppb reduced total biomass of trees by 17% compared with CF controls. The root‐to‐shoot ratio was significantly reduced by elevated [O₃] indicating greater sensitivity of root biomass to [O₃]. At elevated [O₃], trees had significant reductions in leaf area, Rubisco content and chlorophyll content which may underlie significant reductions in photosynthetic capacity. Trees also had lower transpiration rates, and were shorter in height and had reduced diameter when grown at elevated [O₃]. Further, at elevated [O₃], gymnosperms were significantly less sensitive than angiosperms. There were too few observations of the interaction of [O₃] with elevated [CO₂] and drought to conclusively project how these climate change factors will alter tree responses to [O₃]. Taken together, these results demonstrate that the carbon‐sink strength of northern hemisphere forests is likely reduced by current [O₃] and will be further reduced in future if [O₃] rises. This implies that a key carbon sink currently offsetting a significant portion of global fossil fuel CO₂ emissions could be diminished or lost in the future.     

Coexistence of two species of Binella Motchulsky (Coleoptera: Ptiliidae) and the significance of their adaptation to different temperature ranges

Abstract.

• 1 Ptinella aptera and Ptinella errabunda often coexist where their distributions overlap.
• 2 The ecological requirements of P.aptera and P.errabunda are similar. Both are generalized mycetophages restricted to the same subcortical habitat of trees in a particular state of decay. Relative humidity appears important in determining habitat suitability for both species, neither of which survived in laboratory regimes below approximately 100% relative humidity.
• 3 In laboratory studies the beetles differed in their response to temperature. Recorded maxima for activity and rate of increase were at higher temperatures for P.aptera than for Perrabunda.
• 4 Temperatures which ‘Ptinella were exposed to in the laboratory occur in natural conditions under bark. Their effects on the species’ distributions are considered.
• 5 The differential temperature adaptations of P.aptera and P.errabunda were probably evolved in allopatry, in response to different environmental conditions. In view of this, it is unreasonable to infer past interspecies competition from these niche differences.
• 6 The niche difference between coexisting Ptinella species is discussed in the light of current ideas concerning the relative importance of competition and other factors in natural communities.

     

Destination‐based seed dispersal homogenizes genetic structure of a tropical palm

As the dominant seed dispersal agents in many ecosystems, frugivorous animals profoundly impact gene movement and fine‐scale genetic structure of plants. Most frugivores engage in some form of destination‐based dispersal, in that they move seeds towards specific destinations, resulting in clumped distributions of seeds away from the source tree. Molecular analyses of dispersed seeds and seedlings suggest that destination‐based dispersal may often yield clusters of maternal genotypes and lead to pronounced local genetic structure. The long‐wattled umbrellabird Cephalopterus penduliger is a frugivorous bird whose lek mating system creates a species‐specific pattern of seed dispersal that can potentially be distinguished from background dispersal processes. We used this system to test how destination‐based dispersal by umbrellabirds into the lek affects gene movement and genetic structure of one of their preferred food sources Oenocarpus bataua, a canopy palm tree. Relative to background dispersal processes, umbrellabird mating behaviour yielded more diverse seed pools in leks that included on average five times more seed sources and a higher incidence of long‐distance dispersal events. This resulted in markedly lower fine‐scale spatial genetic structure among established seedlings in leks than background areas. These species‐specific impacts of destination‐based dispersal illustrate how detailed knowledge of disperser behaviour can elucidate the mechanistic link driving observed patterns of seed movement and genetic structure.     

SENSORY EXPECTATIONS OF CHILDREN FROM DIFFERENT HOUSEHOLD INCOMES FOR A BRANDED CONFECTIONARY PRODUCT

The influence of brand and price on the sensory acceptability of alfajor (an individual cake covered in chocolate) among children from different household incomes was measured. Two brands of alfajores, “cheap” and “expensive,” were used. A total of 120 children, half from low‐income households (LI) and half from medium‐ to high‐income households (M–HI), participated in the study. They tasted the alfajores in three conditions: blind, package‐alone and package + product. The LI children were not influenced by brand. For the M–HI children, an assimilation effect was observed. The findings highlight the importance of socioeconomic factors in sensory expectation. In the blind condition, if the price is very high, no matter how much a child likes an alfajor he/she will not buy it. If the price is low, the overall liking will highly influence the choice. Implications of results for manufacturers, money providers and nutritional education agencies are discussed.     

Anthropologies of Violence and Resistance

Encounters with Violence in Latin America: Urban Poor Perceptions from Colombia and Guatemala. Caroline O. N. Moser and Cathy McIlwaine. New York: Routledge, 2004. 272 pp.
Violence: Theory and Ethnography. Pamela J. Stewart and Andrew Strathern. New York: Continuum, 2002. 196 pp.
Shadows of War: Violence, Power, and International Profiteering in the Twenty-First Century. Carolyn Nordstrom. Berkeley: University of California Press, 2004. 293 pp.     

Hox Genes and Segmental Patterning of the Vertebrate Hindbrain

SYNOPSIS. Pattern formation in the developing hindbrain andcranio-facial region has been studied in a range of vertebrateorganisms. The developing hindbrain is transiently segmentedinto units termed rhombomeres which correspond with domainsof gene expression, lineage restriction and neuronal organizationand serve to coordinate the migration of cranial neural crestinto the adjacent branchial arches. In this paper I review thecellular and molecular events underlying both hindbrain segmentationand the acquisition of segmental identity, consolidating recentresults from different model systems. Data suggesting that thevertebrate Hox genes play an important role in specifying positionalvalue to the rhombomeres and cranial neural crest are also examined.I compare expression patterns of the Hox genes between speciesand consider the mechanisms involved in controlling their appropriatespatial regulation. In addition I describe a recently characterizedzebraflsh hindbrain segmentation mutant, Valentino; morphological,cellular and gene expression data for this mutant are helpingto further our understanding of hindbrain patterning.