Use of fragment–sharing estimates from DNA fingerprinting to determine relatedness in a tropical wren

We assessed the usefulness of DNA fragment–sharing scores from DNA fingerprints for assigning relatedness to unknown pairs of individuals in a population of stripe–backed wrens (Campylorhynchus nuchalis). Preliminary investigation of scoring biases revealed consistency both within and between scorers in relative band–sharing scores, but a tendency for scores to be inflated and for inter–scorer agreement to decline as distance between lanes on an autoradiograph increased. Distributions of band–sharing values matched expected distributions well, which suggests that variability in scores is mostly inherent and not a result of errors in scoring. Confidence intervals based on band–sharing scores or means of scores across enzymes, probes and scorers revealed that unrelated (r= 0) and first–order dyads (r=Vi) could be distinguished on the basis of single band–sharing scores from the best combination of enzyme and probe (HaeIII/33.15) and that first– and second–order dyads could be distinguished when confidence intervals were based on means of band–sharing scores across two enzymes, two probes and two scorers.     

Dinosaur Evolution: Student Response to Dinosaur Ramblings

Abstract: In the 2007 Journal of Wildlife Management article “Dinosaur Ramblings,” Scalet described a shift in university and agency programs away from applied management research toward basic ecological research. We interpret Scalet's commentary as primarily synonymizing applied management research to game management and basic ecological research to nongame management and theoretical research. Although we agree with Scalet that a change in management practices has occurred, we believe that change is more an integration of applied and basic research as opposed to a shift away from management. We provide a hierarchical framework to alternatively explain Scalet's perceived shift in which we place applied management and basic theoretical research under the science of ecology. We believe integration of basic and applied research has been driven by the evolving structure of society and the public's changing view of natural resources. The integration of basic and applied research is necessary for informed and, thence, better management practices.     

The development of an action threshold for cabbage aphid (Brevicoryne brassicae) in oilseed rape in the UK

Replicated small plot field experiments were done at two sites growing winter oilseed rape (ADAS Boxworth, Cambridgeshire and ADAS High Mowthorpe, North Yorkshire) and two sites growing spring oilseed rape (ADAS Bridgets, Hampshire and ADAS Rosemaund, Herefordshire) to investigate the effect of cabbage aphid (Brevicoryne brassicae) on crop yield and quality. All four sites were included in the first 2 yr of the experiment in 1994 and 1995 but only those with winter oilseed rape were continued into the final year in 1996. Plots were artificially inoculated with cabbage aphids at either five aphid 4 m^-2 or 5 aphids 16 m^-2 or left uninoculated to become naturally infested. In 1995 and 1996 the naturally infested treatment was omitted. Sprays of the aphicide pirimicarb at GS 3.3, 3.7, 4.5, 4.9 and 5.5 were used to manipulate aphid populations. Once a plot had been treated at a target growth stage it was sprayed on all subsequent occasions to prevent recolonisation. Aphid numbers were assessed prior to each spray date and their effect on the crop measured in terms of yield of seed and oil and glucosinolate content. Artificial inoculation of aphids was often successful in establishing different populations of the pest at a range of growth stages. Results showed that cabbage aphid sometimes reduced both crop yield and quality. Yield responses to insecticide treatment tended to be larger in spring oilseed rape than in winter oilseed rape mainly because it became more heavily infested at an early growth stage. Tentative thresholds are proposed for control of the pest in both winter and spring oilseed rape. It is stressed that cabbage aphid is a sporadic pest and rarely likely to reach these threshold levels in field crops.     

Assessing the phytotoxicity of mononuclear hydroxy-aluminum

Abstract Al³⁺ is an important rhizotoxic ion in acid soils around the world. Al³⁺ is in equilibrium with mononuclear hydroxy-Al species, such as AlOH²⁺ and AL(OH)₂⁺, but the toxicity of these species has not been determined. Polynuclear Al may also coexist with Al³⁺, and one of these species, AlO₄Al₁₂(OH)₂₄(H₂O)₁₂⁷⁴, is very toxic. In order to determine the toxicity of mononuclear hydroxy-Al we have reanalysed the results of previously published, solution-culture experiments and have performed new experiments. Several problems are inherent in these studies. At pH values less than 5.0, the activities of the mononuclear hydroxy-Al species are low relative to Al³⁺, but attempts to change the ratio by raising the pH generally initiate the formation of polynuclear Al. (We discovered that mononuclear solutions are stable for many days when {Al³⁺}/{H⁺}³≤ 10^8.8, where braces denote activities.) We avoided, or accounted for, polynuclear Al in our studies. In addition, we used up-to-date equilibrium constants to compute Al species, very simple culture media (generally containing CaCl₂, AlCl₃ and HCl as the only inputs), short-term (2d) growth, and an Al-sensitive wheat variety (Triticum aestivum L. cv. Tyler) that permitted low Al levels and, consequently, higher pH values without Al polymerization. Experiments were designed in which the solutions were constant in {Al³⁺} and variable in mononuclear hydroxy-Al or were orthonal (factorial) in {Al³⁺} and {AlOH²⁺}. Linear and nonlinear, simple and multiple, regression analyses of these and previous experiments failed to reveal any toxicity for mononuclear hydroxy-Al to Tyler wheat.     

The citrus leaf cuticle in relation to measurement of leaf water potential using thermocouple psychrometers*

Abstract. Cuticular resistance to water vapour diffusion is an important aspect of thermocouple psychrometry and may introduce significant error in the measurement of leaf water potential (Ψ). The effect of the citrus (Citrus mitis Blanco) leaf cuticle on water vapour movement was studied using the times required for vapour pressure equilibration during thermocouple psychrometric measurement of Ψ. Cuticular abrasion with various carborundum powders was used to reduce the diffusive resistance of both the adaxial and abaxial leaf surfaces, and the extent of the disruption to the leaf was investigated with light and electron microscopy. Cuticular abrasion resulted in reduced equilibration times due to decreased cuticular resistance and greater water vapour movement between the leaf and the psychrometer chamber. Equilibration times were reduced from over 5 h in the unabraded control leaves to 1 h with cuticle abrasion. This was associated with the decrease in diffusive resistance with cuticular abrasion from over 55 s cm^?1 to less than 8 s cm^?1 for both the adaxial and abaxial leaf surfaces. Scanning electron micrographs of the abraded leaf tissue revealed considerable disruption of the stomatal ledge and of the guard cells, surface smoothing and displacement of waxes into the stomatal aperture, and damage to veins. Observations with the transmission electron microscope revealed frequent disruption of epidermal cell walls, and damage to both the cytoplasmic and vacuolar membranes.     

Ecological role of control agent,and not just host‐specificity,determine risks of biological control

Biological control agents used to manage alien vegetation are generally viewed as providing an ecosystem service, owing to reduced ecological and economic costs of invasion following their release. In particular, gall‐formers are popular as biological control agents because they are host‐specific and therefore considered low risk. However, galls can also be considered to be ecological engineers, because they provide nutritional resources for native invertebrates. We tested whether native invertebrates had formed associations with the gall‐forming fungus Uromycladium tepperianum, introduced into South Africa to control the Australian invasive alien tree Acacia saligna, by collecting U. tepperianum galls and monitoring emergence. We found that a number of invertebrates had formed associations with the biological control agent, among which was the important citrus pest, Thaumatotibia leucotreta (false codling moth). We used pheromone‐baited traps to ascertain if this supplementary source of T. leucotreta increased their abundance in orchards close to patches of gall host, but did not find this to be the case. We did find, however, that control measures used by farmers explained T. leucotreta abundances in traps, which may have obscured detection of any effects of a nearby host for the pest. Nevertheless, this study illustrates the first case of a host‐specific classical biological control agent providing resources for an economically significant crop pest. We conclude that although biological control agents are strictly vetted to ensure host‐specificity, introduced biological control agents that become abundant and can act as ecological engineers pose risks when native biota form associations with them, resulting in a number of possible cascading ecosystem effects. In addition, there could be economic consequences when these associated species include agricultural pests. We conclude that not just host specificity, but potential ecological effects of biological control agents, should be considered in their selection.     

Sperm (ejaculate) competition in Drosophila melanogaster, and the reproductive value of females to males in relation to female age and mating status

• 1 In double mating experiments with Drosophila melanogaster in which one male had been irradiated, it was confirmed that sperm displacement is extensive, i.e. the second male to mate displaces most of the previously-stored sperm.
• 2 The predominance of the second ejaculate over the first increases with the interval between the two matings, from about P₂= 0.83 (second mating on the first day after the first mating) to about P₂= 0.99 (interval between mating = 14 days) where P₂ is the proportion of offspring fathered by the second male.
• 3 A more accurate method for calculating P₂ values is developed for experiments in which sperm are ‘labelled’ by irradiation treatment (equation 1).
• 4 Observations of the reducing egg production of the female throughout life were also obtained. A model is examined which incorporates both the sperm competition and egg production data to predict the reproductive value to a male of a mating with a given type of female, varying in age and mating status. The relative value (in terms of probable numbers of progeny gained) of a mating with a virgin or 4 day post-mating female is about twice that of a 14 day post-mating female, mainly because of the fecundity difference.
• 5 Some evolutionary aspects of sperm competition and multiple mating in insects are reviewed and discussed.

     

Multiple aspects of condition influence a heritable sexual trait: a synthesis of the evidence for capture of genetic variance in red junglefowl

A long‐standing question in the study of sexual selection is: if an attractive male trait signals heritable aspects of quality, how does genetic variation associated with that trait persist in the face of directional selection? It has been proposed that sensitivity to condition in general could allow a sexual signal to show heritable variation even under persistent directional selection. The multitude of genes underlying components of condition present a large target for mutation, and so genetic variance in condition may not be readily exhausted by selection. Insights gained in studies of the red junglefowl are relevant to this hypothesis, and provide a model for research in other systems. The fleshy comb of male red junglefowl is among the best‐studied sexual signals. Multiple components of condition, such as health, immune function, testosterone, and social status, influence comb growth, and, in the present study, we provide the first comprehensive integration of this large body of evidence to lay out the compelling case for condition‐dependence of the junglefowl comb. Variation in comb size is heritable and, most important to this issue, is genetically correlated with heritable variation in a body condition index. Although understanding of the red junglefowl's comb is far from complete, it exceeds our understanding of many other sexual signals and provides an empirical model for the study of condition‐dependent signals in general. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 651–660.