Detection of dengue viral RNA in Aedes aegypti (Diptera : Culicidae) exposed to sticky lures using reverse-transcriptase polymerase chain reaction

Active surveillance for dengue (DEN) virus infected mosquitoes can be an effective way to predict the risk of dengue infection in a given area. However, doing so may pose logistical problems if mosquitoes must be kept alive or frozen fresh to detect DEN virus. In an attempt to simplify mosquito processing, we evaluated the usefulness of a sticky lure and a seminested reverse-transcriptase polymerase chain reaction assay (RT-PCR) for detecting DEN virus RNA under laboratory conditions using experimentally infected Aedes aegypti (L.) mosquitoes. In the first experiment, 40 male mosquitoes were inoculated with 0.13 mul of a 10(4) pfu/ml DEN-2 stock solution. After a 7-d incubation period, the mosquitoes were applied to the sticky lure and kept at room temperatures of 23-30 degreesC. Following 7,10,14, and 28 d application, 10 mosquitoes each were removed from the lure pooled and assayed for virus. DEN virus nucleic acid was clearly detectable in all pools up to 28 d after death. A second study evaluated sensitivity and specificity using one, two, and five DEN-infected mosquitoes removed after 7, 10, 14, 21 and 30 d application and tested by RT-PCR. All four DEN serotypes were individually inoculated in mosquitoes and evaluated using the same procedures as experiment 1. The four serotypes were detectable in as few as one mosquito 30 d after application to the lure with no evidence of cross-reactivity. The combination of sticky lures and RT-PCR show promise for mosquito and dengue virus surveillance and warrant further evaluation.

Foraging by the endangered black-breasted button-quail (Turnix melanogaster) within fragmented rainforest of an agricultural landscape

We studied the foraging habitat of the endangered black-breasted button-quail (Turnix melanogaster) in 13 rainforest patches of an agricultural landscape (23.4 km(2)) in eastern Australia to assess its use of fragmented habitats outside conservation reserves. The species foraged only in the three largest patches (17.4, 40.0, 63.8 ha in size), all of which were connected to open eucalypt forest, and in intact rainforest. Occurrence of birds was greatest in the largest patch. The maximum number of individuals within the study area was estimated to be 22. Radio-tracking of nine birds revealed that three were resident in the largest patch for periods of over 100 days; no movements between patches were detected. Three radio-tagged birds were taken by avian and mammalian predators. Our results indicated that the long-term future of the species in agricultural landscapes is bleak and that management action is urgently needed to arrest its decline in these ecosystems, (C) 2001 Elsevier Science Ltd. All rights reserved.

Habitat complexity, spatial interference, and "minimum risk distribution": a framework for population stability

In the past century, the debate over whether or not density-dependent factors regulate populations has generally focused on changes in mean population density, ignoring the spatial variance around the mean as unimportant noise. In an attempt to provide a different framework for understanding population dynamics based on individual fitness, this paper discusses the crucial role of spatial variability itself on the stability of insect populations. The advantages of this method are the following: (1) it is founded on evolutionary principles rather than post hoc assumptions; (2) it erects hypotheses that can be tested; and (3) it links disparate ecological schools, including spatial dynamics, behavioral ecology, preference-performance, and plant apparency into an overall framework. At the core of this framework, habitat complexity governs insect spatial variance. which in turn determines population stability. First, the minimum risk distribution (MRD) is defined as the spatial distribution of individuals that results in the minimum number of premature deaths in a population given the distribution of mortality risk in the habitat (and, therefore, leading to maximized population growth). The greater the divergence of actual spatial patterns of individuals from the MRD, the greater the reduction of population growth and size from high, unstable levels. Then, based on extensive data from 29 populations of the processionary caterpillar, Ochrogaster lunifer, four steps are used to test the effect of habitat interference on population growth rates. (1) The costs (increasing the risk of scramble competition) and benefits (decreasing the risk of inverse density-dependent predation) of egg and larval aggregation are quantified. (2) These costs and benefits, along with the distribution of resources, are used to construct the MRD for each habitat. (3) The MRD is used as a benchmark against which the actual spatial pattern of individuals is compared. The degree of divergence of the actual spatial pattern from the MRD is quantified for each of the 29 habitats. (4) Finally, indices of habitat complexity are used to provide highly accurate predictions of spatial divergence from the MRD, showing that habitat interference reduces population growth rates from high, unstable levels. The reason for the divergence appears to be that high levels of background vegetation (vegetation other than host plants) interfere with female host-searching behavior. This leads to a spatial distribution of egg batches with high mortality risk, and therefore lower population growth. Knowledge of the MRD in other species should be a highly effective means of predicting trends in population dynamics. Species with high divergence between their actual spatial distribution and their MRD may display relatively stable dynamics at low population levels. In contrast, species with low divergence should experience high levels of intragenerational population growth leading to frequent habitat-wide outbreaks and unstable dynamics in the long term. Six hypotheses, erected under the framework of spatial interference, are discussed, and future tests are suggested.

Mathematical methods for spatially cohesive reserve design

The problem of designing spatially cohesive nature reserve systems that meet biodiversity objectives is formulated as a nonlinear integer programming problem. The multiobjective function minimises a combination of boundary length, area and failed representation of the biological attributes we are trying to conserve. The task is to reserve a subset of sites that best meet this objective. We use data on the distribution of habitats in the Northern Territory, Australia, to show how simulated annealing and a greedy heuristic algorithm can be used to generate good solutions to such large reserve design problems, and to compare the effectiveness of these methods.

Patchy populations in stochastic environments: Critical number of patches for persistence

We introduce a model for the dynamics of a patchy population in a stochastic environment and derive a criterion for its persistence. This criterion is based on the geometric mean (GM) through time of the spatial-arithmetic mean of growth rates. For the population to persist, the GM has to be greater than or equal to1. The GM increases with the number of patches (because the sampling error is reduced) and decreases with both the variance and the spatial covariance of growth rates. We derive analytical expressions for the minimum number of patches (and the maximum harvesting rate) required for the persistence of the population. As the magnitude of environmental fluctuations increases, the number of patches required for persistence increases, and the fraction of individuals that can be harvested decreases. The novelty of our approach is that we focus on Malthusian local population dynamics with high dispersal and strong environmental variability from year to year. Unlike previous models of patchy populations that assume an infinite number of patches, we focus specifically on the effect that the number of patches has on population persistence. Our work is therefore directly relevant to patchily distributed organisms that are restricted to a small number of habitat patches.

Stream-bank shade and larval distribution of the Philippine malaria vector Anopheles flavirostris

The principal malaria vector in the Philippines, Anopheles flavirostris (Ludlow) (Diptera: Culicidae), is regarded as 'shade-loving' for its breeding sites, i.e. larval habitats. This long-standing belief, based on circumstantial observations rather than ecological analysis, has guided larval control methods such as 'stream-clearing' or the removal of riparian vegetation, to reduce the local abundance of An. flavirostris . We measured the distribution and abundance of An. flavirostris larvae in relation to canopy vegetation cover along a stream in Quezon Province, the Philippines. Estimates of canopy openness and light measurements were obtained by an approximation method that used simplified assumptions about the sun, and by hemispherical photographs analysed using the program hemiphot(C) . The location of larvae, shade and other landscape features was incorporated into a geographical information system (GIS) analysis. Early larval instars of An. flavirostris were found to be clustered and more often present in shadier sites, whereas abundance was higher in sunnier sites. For later instars, distribution was more evenly dispersed and only weakly related to shade. The best predictor of late-instar larvae was the density of early instars. Distribution and abundance of larvae were related over time (24 days). This pattern indicates favoured areas for oviposition and adult emergence, and may be predictable. Canopy measurements by the approximation method correlated better with larval abundance than hemispherical photography, being economical and practical for field use. Whereas shade or shade-related factors apparently have effects on larval distribution of An. flavirostris , they do not explain it completely. Until more is known about the bionomics of this vector and the efficacy and environmental effects of stream-clearing, we recommend caution in the use of this larval control method.

Cleaning symbioses from the parasites' perspective

Cleaning behaviour has generally been viewed from the cleaner or client's point of view. Few studies, however, have examined cleaning behaviour from the parasites' perspective, yet they are the equally-important third players in such associations. All three players are likely to have had their evolution affected by the association. As cleaner organisms are important predators of parasites, cleaners are likely to have an important effect on their prey. Little, however, is known of how parasites are affected by cleaning associations and the strategies that parasites use in response to cleaners. I examine here what parasites are involved in cleaning interactions, the effect cleaners have on parasites, the potential counter-adaptations that parasites have evolved against the predatory activities of cleaner organisms, the potential influence of cleaners on the life history traits of parasites, and other factors affected by cleaners. I have found that a wide range of ectoparasites from diverse habitats have been reported to interact with a wide range of cleaner organisms. Some of the life history traits of parasites are consistent with the idea that they are in response to cleaner predation. It is clear, however, that although many cleaning systems exist their ecological role is largely unexplored. This has likely been hindered by our lack of information on the parasites involved in cleaning interactions.

Habitat requirements for the conservation of arboreal marsupials in dry sclerophyll forests of Southeast Queensland, Australia

The habitat requirements of arboreal marsupials were investigated in the dry sclerophyll forests of southeast Queensland, Australia. Species richness and abundance of arboreal marsupials was correlated to the proportion of total stand basal area occupied by lemon-scented gum (Corymbia citriodora), the height of the tallest trees, and density of hollow-bearing trees. The first two factors suggested that the most productive forests were also the most suitable habitats for arboreal marsupials. Importantly, the number of hollow-bearing trees was a significant factor in determining species richness and abundance of arboreal marsupials in this study, with the maximum number of species reached at sites containing greater than or equal to4 hollow-bearing trees/ha, and maximum abundance occurring at sites with :6 hollow-bearingtrees/ha. The proportion of C. citriodora was significant for the presence of the common brushtail possum (Trichosurus vulpecula), greater glider (Petauroides volans), and the yellow-bellied glider (Petaurus australis), while understory Acacia sp. density was important for the presence of the sugar glider (Petaurus breviceps). The yellow-bellied glider was also affected by two other variables: the density of hollow-bearing trees >50 cm diameter at breast height (dbh), and the time since the last logging. Current Codes of Practice regulating the density of hollow-bearing trees and silvicultural practices in state-owned timber production forests appear to provide adequate protection for arboreal marsupials, but the recently introduced increase in timber extraction rates within state forests may be detrimental to the animals. Also, protective prescriptions do not apply to the privately owned and leasehold estates, which contain the majority of the dry sclerophyll forests in southeast Queensland.

Convergent maternal care strategies in ungulates and macropods

Mammals show extensive interspecific variation in the form of maternal care. Among ungulates, there is a dichotomy between species in which offspring follow the mother (following strategy) versus species in which offspring remain concealed (hiding strategy). Here we reveal that the same dichotomy exists among macropods (kangaroos, wallabies and allies). We test three traditional adaptive explanations and one new life history hypothesis. and find very similar patterns among both ungulates and macropods. The three traditional explanations that we tested were that a ''following'' strategy is associated with (1) open habitat, (2) large mothers, and (3) gregariousness. Our new life-history hypothesis is that a following strategy'' is associated with delayed weaning, and thus with the slow end of the slow-fast mammalian life-history continuum, because offspring devote resources to locomotion rather than rapid growth. Our comparative test strongly supports the habitat structure hypothesis and provides some support for this new delayed weaning hypothesis for both ungulates and macropods. We propose that sedentary young in closed habitats benefit energetically by having milk brought to them. In open habitats, predation pressure will select against hiding. Followers will suffer slower growth to independence. Taken together, therefore, our results provide the first quantitative evidence that macropods and ungulates are convergent with respect to interspecific variation in maternal care strategy. In both clades, differences between species in the form of parental care are due to a similar interaction between habitat, social behavior, and life history.

Interspecific variation in plumage colour among birds: species recognition or light environment?

The traditional explanation for interspecific plumage colour variation in birds is that colour differences between species are adaptations to minimize the risk of hybridization. Under this explanation, colour differences between closely related species of birds represent reproductive character displacement. An alternative explanation is that interspecific variation in plumage colour is an adaptive response to variation in light environments across habitats. Under this explanation, differences in colour between closely related species are a product of selection on signal efficiency. We use a comparative approach to examine these two hypotheses, testing the effects of sympatry and habitat use, respectively, on divergence in male plumage colour. Contrary to the prediction of the Species Isolation Hypothesis, we find no evidence that sympatric pairs of species are consistently more divergent in coloration than are allopatric pairs of species. However, in agreement with the Light Environment Hypothesis, we find significant associations between plumage coloration and habitat use. All of these results remain qualitatively unchanged irrespective of the statistical methodology used to compare reflectance spectra, the body regions used in the analyses, or the exclusion of areas of plumage not used in sexual displays. Our results suggest that, in general, interspecific variation in plumage colour among birds is more strongly influenced by the signalling environment than by the risk of hybridization.

Spatial distribution of benthic microalgae on coral reefs determined by remote sensing

Understanding the ecological role of benthic microalgae, a highly productive component of coral reef ecosystems, requires information on their spatial distribution. The spatial extent of benthic microalgae on Heron Reef (southern Great Barrier Reef, Australia) was mapped using data from the Landsat 5 Thematic Mapper sensor. integrated with field measurements of sediment chlorophyll concentration and reflectance. Field-measured sediment chlorophyll concentrations. 2 ranging from 23-1.153 mg chl a m(2), were classified into low, medium, and high concentration classes (1-170, 171-290, and > 291 mg chl a m(-2)) using a K-means clustering algorithm. The mapping process assumed that areas in the Thematic Mapper image exhibiting similar reflectance levels in red and blue bands would correspond to areas of similar chlorophyll a levels. Regions of homogenous reflectance values corresponding to low, medium, and high chlorophyll levels were identified over the reef sediment zone by applying a standard image classification algorithm to the Thematic Mapper image. The resulting distribution map revealed large-scale ( > 1 km 2) patterns in chlorophyll a levels throughout the sediment zone of Heron Reef. Reef-wide estimates of chlorophyll a distribution indicate that benthic Microalgae may constitute up to 20% of the total benthic chlorophyll a at Heron Reef. and thus contribute significantly to total primary productivity on the reef.

Growth of subtropical ECM fungi with different nitrogen sources using a new floating culture technique

Eight species of ectomycorrhizal (ECM) fungi in the genera Amanita. Gymnoboletus, Lactarius, and Russula were isolated from subtropical plant communities in eastem Australia. Two species were isolated from each of rainforest, Nothofagus forest, Eucalyptus forest, and Eucalyptus dominated wallum (heath) forest. These communities differ strongly in their soluble soil nitrogen (N) composition. The ability of the fungi to use inorganic (nitrate, ammonium) and organic (amide, peptide, protein) nitrogen sources was determined. As the fungi did not grow in liquid culture, a 'floating culture' technique was devised that allows hyphal growth on a screen floating on liquid medium. With some exceptions, fungal biomass production in floating culture closely reflected fungal growth on solid media assessed by total colony glucosamine content. Most isolates grown in floating culture had similar glucosamine concentrations on all N sources, with isolate specific concentrations ranging from 6 to 12 mug glucosamine g(-1) DW. However, Russula spp. had up to 1.7-fold higher glucosamine concentrations when growing with glutamine or ammonium compared to nitrate, glutathione or protein. Floating cultures supplied with 0.5, 1.5. 4.5, or 10 mm N mostly produced greatest biomass with 4.5 mM N. In vitro nitrate reductase activity (NRA) ranged from very low (0.03 mumol NO2- g(-1) fw h(-1)) in Russula sp. (wallum) to high (2.16 mumol NO2- g(-1) fw h(-1)) in Gymnoboletus sp. (rainforest) and mirrored the fungi's ability to use nitrate as a N source. All Russula spp. (wallum, Nothofagus and Eucalyptus forests), Lactarills sp, (rainforest) and.4manita sp. (wallum) utilized ammonium and glutamine but had little ability to use other N sources. In contrast,Amanita species (Nothofagus and Eucalyptus forests) grew on all N sources but produced most biomass with ammonium and glutamine. Only Gymnoboletus sp. (rainforest) showed similar growth with nitrate and ammonium as N sources. Fungal N source use was not associated with taxonomic groups, but is discussed in the context of soil N sources in the different habitats.

Drosophilidae (Diptera) of Australia's Northern Territory: Ecology and biogeography

The drosophilid fauna is well documented in eastern Australia but is poorly known in other parts of the continent. This paper summarises what is known of this fauna in the Northern Territory (NT), and includes results from banana trapping in the humid and arid zones. The 42 recorded species include species that breed in fruit, fungi and/or flowers, and a larval predator of scale insects. Drosophilids occur in all three major climate zones (humid, semiarid and arid) but predominate in the humid zone. Banana-attracted species in the humid zone (wet-dry tropics) were common in all sampled habitats: urban, rainforest and open woodland. They included predominantly urban and/or rainforest species. Of the species collected in open woodland, some are likely to be breeding there, whereas others may have been intercepted during movement across the area. The semiarid fauna is a depauperate version of that found in the humid region. Only three species have been recorded in the arid region: an endemic arid specialist, and two cosmopolitan species (D. simulans and D. melanogaster ) in urban Alice Springs. Overall, the NT drosophilid fauna represents a depauperate version of that found in eastern Australia, probably because of climatic factors and natural barriers to range expansion. There is little evidence of regional endemism, with probably only one (and at most three) species endemic to the NT, and no evidence of independent, natural dispersion from nearby Indonesia.

Propagation of nonstationary curved and stretched premixed flames with multistep reaction mechanisms

The propagation speed of a thin premixed flame disturbed by an unsteady fluid flow of a larger scale is considered. The flame may also have a general shape but the reaction zone is assumed to be thin compared to the flame thickness. Unlike in preceding publications, the presented asymptotic analysis is performed for a general multistep reaction mechanism and, at the same time, the flame front is curved by the fluid flow. The resulting equations define the propagation speed of disturbed flames in terms of the properties of undisturbed planar flames and the flame stretch. Special attention is paid to the near-equidiffusion limit. In this case, the flame propagation speed is shown to depend on the effective Zeldovich number Z(f) , and the flame stretch. Unlike the conventional Zeldovich number, the effective Zeldovich number is not necessarily linked directly to the activation energies of the reactions. Several examples of determining the effective Zeldovich number for reduced combustion mechanisms are given while, for realistic reactions, the effective Zeldovich number is determined from experiments. Another feature of the present approach is represented by the relatively simple asymptotic technique based on the adaptive generalized curvilinear system of coordinates attached to the flame (i.e., intrinsic disturbed flame equations [IDFE]).

Diversity in the Monogenea and Digenea: does lifestyle matter?

If the cestodes are excluded, then the parasitic platyhelminths of fishes divide neatly into the external and monoxenous Monogenea and the internal and heteroxenous Digenea. Both groups have apparently had long associations of coevolution, host switching and adaptation with fishes and have become highly successful in their respective habitats. Current estimates of species richness for the two groups suggest that they may be remarkably similar. Here we consider the nature of the diversity of the Monogenea. and Digenea of fishes in terms of richness of species and higher taxa to determine what processes may be responsible for observed differences. The Monogenea includes at least two super-genera (Dactylogyrus and Gyrodactylus) each of which has hundreds of species, no comparable genera are found in the Digenea. Possible reasons for this difference include the higher host specificity of monogeneans and their shorter generation Lime. If allowance is made for the vagaries of taxonomic 'lumping' and 'splitting', then there are probably comparable numbers of families of monogeneans and digeneans in fishes. However, the nature of the families differ profoundly. Richness in higher taxa (families) in the Digenea is explicable in terms of processes that appear to have been unimportant in the Monogenea. Readily identifiable sources of diversity in the Digenea are: recolonisation of fishes by taxa that arose in association with tetrapods; adoption of new sites within hosts; adoption of new diets and feeding mechanisms; adaptations relating to the exploitation of ecologically similar groups of fishes and second intermediate hosts; and adaptations relating to the exploitation of phylogenetic lineages of molluscs. In contrast, most higher- level monogenean diversity (other than that associated with the subclasses) relates principally to morphological specialisation for attachment by the haptor. (C) 2002 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.