Identification of ichneumonid wasps using image analysis of wings

Abstract. Image analysis was used to measure the morphological characters of wings of five species of Canadian Itoplectis (Ichneumonidae). The procedure to digitize and measure various elements of the wings with an image analyser is outlined. Specimens were assigned to species by discriminant analysis and independent univariate comparisons of 144 characters from cells, veins and vertices. All the fifty specimens used were assigned to the correct species by both methods. Image analysis of ichneumonid wings is an effective alternative to the conventional identification system.     

Propagation of Date Palm (Phoenix dactylifera L.) in vitro

Adventitious plantlets were obtained from lateral buds, shoottips, embryos, and pieces of stem and rachilla tissue of Phoenixdactylifera L. cultured on a modified Murashige and Skoog mediumcontaining 3 mg l^–1 N-(²-isopenty)adenine 0?1–100mg l^–1 -naphthaleneacetic acid or 2,4-dichlorophenoxyaceticacid, and 3 g l^–1 activated charcoal. Additions of auxinswere necessary to induce explants to produce callus, adventitiousplantlets, and roots. Plantlets were obtained from explantscultured 3–4 months in vitro. No difference in growthresponses between male and female explants was observed duringculture. Complex addenda of activated charcoal and polyvinylpyrrolidonewere tested in the nutrient media at various concentrationsto prevent explant browning. Activated charcoal fostered satisfactorygrowth by reducing the browning and inhibition of growth ofexplants.     

Sensitivity to metalaxyl of Phytophthora infestans populations in potato crops in south-west England in 1980 and 1981

A laboratory test was developed to assess the sensitivity of field populations of Phytophthora infestans to metalaxyl. Discs of potato leaf tissue were floated upon solutions of the fungicide at different concentrations and inoculated with spores. The extent of symptom development was noted after incubation under standard conditions for 5–6 days. In preliminary experiments growth of isolates of P. infestans obtained from culture collections was severely inhibited in discs treated at 2 μg/ml. By contrast the development of an isolate obtained from a crop in Eire in which blight control with metalaxyl had failed, and known to be markedly less sensitive in vitro, was unaffected in discs treated at 100 μg/ml. During the summer of 1980, 234 samples of P. infestans were obtained from 20 sites in south-west England, 10 of which had received sprays containing metalaxyl and 10 of which had not. All samples were sensitive to metalaxyl applied at 2 μg/ml. In 1981, 35 sites within the same area, 30 of which had received sprays containing either metalaxyl or ofurace (a related fungicide), were similarly surveyed. Most of the 79 samples of P. infestans examined proved sensitive and at all sites the amount of blight was small. However, at three sites, including one not treated with acylalanine fungicides, strains were found which were unaffected by 100 μg/ml metalaxyl in leaf disc tests. These findings are discussed in relation to the development of resistant blight in other areas and to the use of fungicide mixtures.     

Covert Categories and Folk Taxonomies

Much of the recent work in ethnoscience has been concerned with the nature of folk taxonomies, an often stated definition of which requires that all folk taxa be monolexemically labeled. This paper offers evidence that unlabeled categories may also be of crucial taxonomic significance, and we feel that it is inappropriate to treat such categories apart from the named taxonomic entities of the system. More importantly, evidence presented indicates that by recognizing unnamed taxa one may gain an understanding of the structure of a particular semantic domain that is actually obscured if one focuses solely on lexically labeled units.     

PCR primers for polymorphic microsatellite loci in the plant‐ant Azteca ulei cordiae (Formicidae: Dolichoderinae)

Twelve microsatellite loci were isolated from the Peruvian tropical plant‐ant, Azteca ulei cordiae (Hymenoptera: Dolichoderinae). High levels of within‐population variation were observed at most loci, with number of alleles ranging from four to 18, and heterozygosity from 0.118 to 1 per population sample. Cross‐species amplification of these loci was also successfully tested in several other species of the same ant genus Azteca.     

Endocrine effects of social stimuli on maturing queens of the dampwood termite Zootermopsis angusticollis

Abstract.  The reproductive physiology of social insects is often highly responsive to social stimuli from nestmates, but the mechanisms underlying this sensitivity are usually poorly understood. The effect of varied social conditions on the endocrinology and ovarian maturation in maturing female primary reproductives of the dampwood termite Zootermopsis angusticollis Hagen is studied to better understand their developmental responses to conspecifics. Newly dealate queens are paired with a reproductive male, with another maturing female, or are allowed to mature in isolation. Developmental responses are tracked by monitoring rates of juvenile hormone (JH) production by corpora allata in vitro , haemolymph ecdysteroids titres and ovarian development after 5, 10, 15 and 30 days of maturation. Significant declines in rates of JH production rates are observed by days 5, 10 and 30, respectively, for females paired with males, left to mature in isolation or paired with a female. Ecdysteroid titres increase by day 5 and stay elevated in females nesting with males. By contrast, for CA from females that are isolated or paired with another female, the titres decline and stay low until at least day 15, but increase significantly by day 30. These hormonal differences correspond to differential rates of physiological maturation, with more rapid ovarian development occurring in females paired with a male, than in those nesting alone or with another female. The results suggest that JH and ecdysteroids modulate the ovarian response of alates to stimuli from nestmates during this period of maturation, and that JH and ecdysteroid titres may be regulated independently during this period of development.     

Hardening trumps acclimation in improving cold tolerance of Drosophila melanogaster larvae

Abstract Chill‐susceptible insects are able to improve their survival of acute cold exposure over both the short term (i.e. hardening at a relatively severe temperature) and longer term (i.e. acclimation responses at milder temperatures over a longer time frame). However, the mechanistic overlap of these responses is not clear. Four larval stages of four different strains of Drosophila melanogaster are used to test whether low temperature acclimation (10 °C for 48 h) improves the acute cold tolerance (LT₉₀, ～2 h) of larvae, and whether acclimated larvae still show hardening responses after brief exposures to nonlethal cold or heat, or a combination of the two. Acclimation results in increased cold tolerance in three of four strains, with variation among instars. However, if acclimation is followed by hardening pre‐treatments, there is no improvement in acute cold survival. It is concluded that short‐term thermal responses (e.g. hardening) may be of more ecological relevance to short‐lived life stages such as larvae, and that the mechanisms of low temperature hardening and acclimation in D. melanogaster may be antagonistic, rather than complementary.     

HOW DID LIFE BECOME SO DIVERSE? THE DYNAMICS OF DIVERSIFICATION ACCORDING TO THE FOSSIL RECORD AND MOLECULAR PHYLOGENETICS

Abstract: The long‐term diversification of life probably cannot be modelled as a simple equilibrial process: the time scales are too long, the potential for exploring new ecospace is too large and it is unlikely that ecological controls can act at global scales. The sum of many clade expansions and reductions, each of which happens according to its own dynamic, probably approximates more a damped exponential curve when translated into a global‐scale species diversification curve. Unfortunately, it is not possible to plot such a meaningful global‐scale species diversification curve through time, but curves at higher taxonomic levels have been produced. These curves are subject to the vagaries of the fossil record, but it is unlikely that the sources of error entirely overwhelm the biological signal. Clades radiate when the external and internal conditions are right: a new territory or ecospace becomes available, and the lineage has acquired a number of characters that open up a new diet or mode of life. Modern high levels of diversity in certain speciose clades may depend on such ancient opportunities taken. Dramatic climatic changes through the Quaternary must have driven extinctions and originations, but many species responded simply by moving to more favourable locations. Ecological communities appear to be no more than merely chance associations of species, but there may be real interactions among species. Ironically, high species diversity may lead to more speciation, not, as had been assumed, less: more species create more opportunities and selective pressures for other species to respond to, rather than capping diversity at a fixed equilibrium level. Studies from the scale of modern ecosystems to global long‐term patterns in the fossil record support a model for the exponential diversification of life, and one explanation for a pattern of exponential diversification is that as diversity increases, new forms become ever more refinements of existing forms. In a sense the world becomes increasingly divided into finer niche space. Organisms have a propensity to speciate freely, species richness within ecosystems appears to generate opportunities for more speciation, clades show all kinds of patterns from sluggish speciation rates and constant diversity through time to apparently explosive speciation, and there is no evidence that rapidly speciating clades have reached a limit, nor that they are driving other clades to extinction. A corollary of this view is that current biodiversity must be higher than it has ever been. Limits to infinite growth are clearly local, regional, and global turnover and extinction events, when climate change and physical catastrophes knock out species and whole clades, and push the rising exponential curve down a notch or two.