[Show abstract][Hide abstract] ABSTRACT: Dengue is the most prevalent global arboviral disease that affects over 300 million people every year. Brazil has the highest number of dengue cases in the world, with the most severe epidemics in the city of Rio de Janeiro (Rio). The effective control of dengue is critically dependent on the knowledge of population genetic structuring in the primary dengue vector, the mosquito Aedes aegypti. We analyzed mitochondrial and nuclear genome-wide SNP markers generated via Restriction-site Associated DNA sequencing, as well as traditional microsatellite markers in Ae. aegypti from Rio. We found four divergent mitochondrial lineages and a strong spatial structuring of mitochondrial variation, in contrast to the overall nuclear homogeneity across Rio. Despite a low overall differentiation in the nuclear genome, we detected strong spatial structure for variation in over 20 genes that have a significantly altered expression in response to insecticides, xenobiotics and pathogens, including the novel biocontrol agent Wolbachia. Our results indicate that high genetic diversity, spatially unconstrained admixing likely mediated by male dispersal, along with locally heterogeneous genetic variation that could affect insecticide resistance and mosquito vectorial capacity, set limits to the effectiveness of measures to control dengue fever in Rio.
[Show abstract][Hide abstract] ABSTRACT: AimSpatial models of the impacts of climate change generally assume that species are restricted to their realized niche, and will persist only if that niche remains accessible through time. However, species often have physiological limits beyond the range of environmental conditions experienced in their present realized niche, and these limits may also be extended further through evolution in response to the selection pressure provided by climate change. Our aim was to develop a general framework for incorporating key parameters relating to physiological limits and adaptive evolution into models of the impact of climate change.LocationGlobal.Methods
Four types of parameter are defined in our framework: the realized limit, the current physiological limit, the evolutionary physiological limit and the rate of adaptive evolution. These parameters can be estimated or predicted using a variety of information sources, and can be applied to a diverse range of modelling approaches.ResultsWe illustrate the utility of this approach by describing how parameters can be measured directly for model species, and by exploring how minimal information on phylogeny and distribution might enable parameter estimation for less well-studied species. We outline a general strategy for deriving these parameters from ongoing research, involving a cascading hierarchy of information ranging from direct observations of traits closely linked to the parameters of interest (e.g. from physiological or evolutionary experimentation) through to more distal indicators (e.g. ecological traits such as niche position or range size).Main conclusionsThe incorporation of adaptive capacity into spatial modelling of biological responses to climate change is now eminently achievable. Significant sources of data are available that can be used as predictors or indicators of physiological limits and the capacity for adaptive evolution in non-model organisms. These data offer a common currency for addressing one of the most important limitations of current efforts to model the impacts of climate change on biological distributions.
[Show abstract][Hide abstract] ABSTRACT: The small heat shock protein (sHsp) family is thought to play an important role in protein refolding and signal transduction, and thereby protect organisms from stress. However little is known about sHsp function and conservation across phylogenies. In the current study, we provide a comprehensive assessment of small Hsp genes and their stress responses in the oriental fruit moth (OFM), Grapholita molesta. Fourteen small heat shock proteins of OFM clustered with related Hsps in other Lepidoptera despite a high level of variability among them, and in contrast to the highly conserved Hsp11.1. The only known lepidopteran sHsp ortholog (Hsp21.3) was consistently unaffected under thermal stress in Lepidoptera where it has been characterized. However the phylogenetic position of the sHsps within the Lepidoptera was not associated with conservation of induction patterns under thermal extremes or diapause. These findings suggest that the sHsps have evolved rapidly to develop new functions within the Lepidoptera.
PLoS ONE 07/2015; 10(7):e0132700. DOI:10.1371/journal.pone.0132700 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutations in the voltage-sensitive sodium channel gene (Vssc) have been identified in Aedes aegypti and some have been associated with pyrethroid insecticide resistance. Whether these mutations cause resistance, alone or in combination with other alleles, remains unclear, but must be understood if mutations are to become markers for resistance monitoring. We describe High Resolution Melt (HRM) genotyping assays for assessing mutations found in Ae. aegypti in Indonesia (F1565C, V1023G, S996P) and use them to test for associations with pyrethroid resistance in mosquitoes from Yogyakarta, a city where insecticide use is widespread. Such knowledge is important because Yogyakarta is a target area for releases of Wolbachia-infected mosquitoes with virus-blocking traits for dengue suppression. We identify three alleles across Yogyakarta putatively linked to resistance in previous research. By comparing resistant and susceptible mosquitoes from bioassays, we show that the 1023G allele is associated with resistance to type I and type II pyrethroids. In contrast, F1565C homozygotes were rare and there was only a weak association between individuals heterozygous for the mutation and resistance to a type I pyrethroid. As the heterozygote is expected to be incompletely recessive, it is likely that this association was due to a different resistance mechanism being present. A resistance advantage conferred to V1023G homozygotes through addition of the S996P allele in the homozygous form was suggested for the Type II pyrethroid, deltamethrin. Screening of V1023G and S996P should assist resistance monitoring in Ae. aegypti from Yogyakarta, and these mutations should be maintained in Wolbachia strains destined for release in this city to ensure that these virus-blocking strains of mosquitoes are not disadvantaged, relative to resident populations.
[Show abstract][Hide abstract] ABSTRACT: Wolbachia are endosymbionts found in many insects with the potential to suppress vector borne diseases, particularly through interfering with pathogen transmission. Wolbachia strains are highly variable in their effects on hosts, raising the issue of which attributes should be selected to ensure that the best strains are developed for disease control. This depends on their ability to suppress viral transmission, invade host populations, persist without loss of viral suppression, and not interfere with other control strategies. The potential to achieve these objectives is likely to involve evolutionary constraints; viral suppression may be limited by the ability of infections to spread due to deleterious host fitness effects. However, there are exceptions to these patterns in both natural infections and in novel associations generated following interspecific transfer, suggesting that pathogen blockage, deleterious fitness effects and changes to reproductive biology might be at least partly decoupled to achieve ideal infection attributes. The stability of introduced Wolbachia and its effects on viral transmission remain unclear, but rapid evolutionary changes seem unlikely. Although deliberate transfers of Wolbachia across species remain particularly challenging, the availability of strains with desirable attributes should be expanded, taking advantage of the diversity available across thousands of strains in natural populations.
[Show abstract][Hide abstract] ABSTRACT: The endosymbiotic bacteria Wolbachia pipientis (wMel strain) has been successfully established in several populations of Aedes aegypti, the primary dengue vector. The virulent Wolbachia strain wMelPop is known to cause several pathological impacts (increased egg mortality, life shortening, etc.) reducing overall fitness in the mosquito Ae. aegypti. Increased egg mortality could substantially reduce egg banks in areas with a lengthy monsoonal dry season, and be employed to eliminate local populations. We tested this application under semi-field cage conditions. First, we determined that wMelPop infection significantly reduced the survival of desiccation-resistant eggs of the dengue vector Ae. aegypti, with shade and temperature having a significant impact; nearly all wMelPop-infected eggs failed to hatch after 6 and 10 weeks in summer and winter conditions, respectively. In laboratory selection experiments we found that egg desiccation resistance can be increased by selection, and that this effect of wMelPop infection is due to the nuclear background of the host rather than Wolbachia. We then conducted an invasion of wMelPop within a semi-field cage using sustained weekly releases of wMelPop infected mosquitoes, with fixation achieved after 9 weeks. The egg populations wMelPop infected and an uninfected control were then subjected to a simulated prolonged monsoonal dry season (2.5 months) before flooding to induce hatching. The wMelPop infected eggs suffered significantly greater mortality than the controls, with only 0.67% and 4.35% of respective infected and uninfected eggs held in 99% shade hatching after 80 days. These studies suggest that wMelPop could be used to locally eliminate populations of Ae. aegypti that are exposed to prolonged dry conditions, particularly if combined with vector control.
[Show abstract][Hide abstract] ABSTRACT: Chironomids from the genus Chironomus are widely used in laboratory ecotoxicology, but are prone to inbreeding depression, which can compromise test results. The standard Chironomus test species (C. riparius, C. dilutus and C. yoshimatsui) are also not cosmopolitan, making it difficult to compare results between geographic regions. In contrast, the chironomid Paratanytarsus grimmii is cosmopolitan, and not susceptible to inbreeding depression because it reproduces asexually by apomictic parthenogenesis. However, there is no standardised culturing methodology for P. grimmii, and a lack of acute toxicity data for common pollutants (metals and pesticides). In this study, we developed a reliable culturing methodology for P. grimmii. We also determined 24-h first instar LC50s for the metals Cu, Pb, Zn, Cd and the insecticide imidacloprid. By developing this culturing methodology and generating the first acute metal and imidacloprid LC50s for P. grimmii, we provide a basis for using P. grimmii in routine ecotoxicological testing.
Bulletin of Environmental Contamination and Toxicology 06/2015; 95(3). DOI:10.1007/s00128-015-1578-5 · 1.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Physiological variation among and within species is thought to play a key role in determining distribution patterns across environmental gradients. We tested inter- and intraspecific variation in cold and heat tolerances for three grasshopper species (genus Kosciuscola) with overlapping elevation distributions, across their respective ranges in the Australian mountains. Of the three cold tolerance traits measured, the critical thermal minimum was the only trait to vary among species, with greater cold tolerance associated with a distribution extending to a higher elevation. Cold tolerance limits were regularly exceeded in exposed microhabitats, suggesting a role for cold adaptation in structuring species distribution patterns. In contrast to cold tolerance, heat tolerance variation was primarily partitioned within species. For two species, populations from treeless alpine habitat were more heat tolerant than their lower-elevation counterparts, supporting recent models that suggest greater exposure to temperature extremes at higher elevations. These contrasting patterns of physiological variation among and within species emphasise the importance of considering variation within species when attempting to understand how species distributions are affected by thermal extremes.This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Alpine ecosystems are globally at risk from climate change. We use the International Union for the Conservation of Nature (IUCN) Red List Criteria for ecosystems to assess the risk of ecosystem collapse in Australian alpine snow patch herbfields. These ecosystems occur on both mainland Australia and Tasmania. They are restricted to steep, south-easterly slopes where snow pack persists well into the summer growing season. Consequently, they are rare, and have high conservation significance. We evaluated the risk of snow patch herbfield ‘ecosystem collapse’ against criteria that accounted for the ecosystem's restricted distribution, projected decline in the snowpack and increased rates of invasion by taller growing native species of shrub and grass. Our analyses revealed considerable uncertainty in estimates of risk based on some criteria, particularly those related to thresholds of ecosystem collapse caused by biotic change. On the basis of the IUCN Red List criteria, we conclude that the ecosystem is ‘endangered’. This is because of the restricted geographical distribution of the ecosystem, a substantial and highly likely decline in the abundance of snow (the principal abiotic driver of the ecosystem), and the prospect of invasion of much of the ecosystem by taller growing native shrubs and grasses. Our case study demonstrates the utility of the Red List methodology for assessing risks to biodiversity in rare ecosystems where changes to both abiotic factors and the relative dominance of native species constitute major threats. Our findings indicate the importance of snow patch herbfields as refugia for dwarf alpine plant species in the face of climate change, the need for continued monitoring, the removal of feral animals from the Australian Alps and scenario planning.
[Show abstract][Hide abstract] ABSTRACT: 1.Thermal tolerance influences the distribution and abundance of many species, but the adaptive capacity of species to increase upper thermal tolerance is poorly understood. Given that patterns of heat tolerance can strongly depend on assay method, it is crucial to get a better understanding of genetic variances and correlations among different heat tolerance components.2.This study tests for correlated responses in different heat tolerance assays in Drosophila melanogaster lines selected for increased heat tolerance following exposure to a static high temperature. Traits tested included heat tolerance measured under static (basal and hardened) and ramping assays (using different starting temperatures and ramping rates), with lines exposed to fluctuating conditions (three days of a cycling temperature regime) and a variable food treatment.3.Selected lines had higher heat tolerance than control lines in all static and ramping assays. The upper thermal tolerance was up to 0.5°C higher in the selected compared to control lines after ten generations of strong selection.4.Selection using a static assay therefore leads to correlated responses in other heat resistant components, suggesting that traits are genetically correlated and not influenced strongly by assay conditions.5.While the D. melanogaster population we studied harbored additive genetic variation to evolve increased upper thermal tolerance, the level detected may be insufficient to keep up with temperature increases predicted under climate change.This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Coccinellidae are important natural enemies of agricultural pests in a variety of crops and there is interest in landscape manipulation to enhance coccinellid populations. Here we investigate impacts of non-crop woody vegetation variables, adjacent crop type and abundance of aphid prey on coccinellid abundance in shelterbelts adjacent to vineyards or pasture near Melbourne, Australia. Sixty sites were sampled five times at monthly intervals using yellow sticky traps. The abundance of coccinellids in shelterbelts was influenced to a greater extent by adjacent crop type and aphid abundance rather than vegetation characteristics like canopy flowers. Abundance of some species was 2-5 times higher in riparian shelterbelts while increased litter depth decreased abundance. When the leaf litter depth of shelterbelts was experimentally increased, the abundance of coccinellids decreased, whereas an experimental decrease in porosity tended to have the opposite effect. These findings suggest that coccinellid abundance can be influenced to some extent by characteristics of shelterbelts, but crop type and prey availability is likely to have a relatively larger impact, perhaps reflecting the high movement rates of this group of natural enemies.
Biological Control 04/2015; 87. DOI:10.1016/j.biocontrol.2015.04.004 · 1.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: DNA barcoding has proven useful for identifying species, and there is increasing interest in this approach to determine species compositions for routine biological monitoring. Generally, DNA barcodes applied to taxa used for monitoring are clearly linked to species, but where taxa are closely related separation using DNA barcodes can be ambiguous. This raises challenges for monitoring, especially if closely related taxa are not recognised as separate species and these species have different environmental responses.Here we examine whether separation of closely related taxa with DNA barcodes is supported by other gene sequences and whether morphological and environmental differences occur among related species that cannot be easily separated. We selected six Chironomidae genera where initial neighbour-joining analysis of DNA barcodes produced monophyletic groups supported by high bootstraps (>95%), but groups were separated by low nucleotide divergence of 3–7%. Taxon separation based on DNA barcodes and mitochondrial cytochrome b (CytB) gene sequences were compared to delineations based on nuclear sequences from the carbomoylphosphate synthase-like gene region 1 (CAD1) and the zinc metalloproteinase (ZMP) gene.Species delineations with DNA barcodes were not always the same as those defined with nuclear sequences, morphological variation or differences in pollution and salinity tolerance. Morphological differences and some environmental differences were often in agreement with taxon separation based on nuclear CAD1 (and ZMP) sequences rather than DNA barcodes (and CytB variation).This study suggests that nuclear sequence data when used in combination with DNA barcodes can help separate closely related taxa into groups useful for routine biological monitoring.
[Show abstract][Hide abstract] ABSTRACT: Background and AimsThere is increasing interest in using natural enemies to control pests in viticulture, but in Australian vineyards, this is often hampered by a lack of information on enemies of particular pest groups. Here we provide an assessment for the first time of the natural enemies of coccids of grapevines.Methods and ResultsThe main coccid pest, Parthenolecanium persicae, was attacked by the parasitoid Metaphycus maculipennis, which constituted 75% of the parasitoids collected from this species. The second most abundant coccid in Australia vineyards, Parthenolecanium pruinosum, was attacked only by one parasitoid, Coccophagus lycimnia. The most common coccinellid predator was Rhyzobius pulchellus, whereas other coccinellids including Cryptolaemus montrouzieri were less common. Several other coleopteran species as well as the moth Mataeomera dubia and several neuroptera are also likely to be important coccid predators.Conclusions
These results point to a complex and much wider range of natural enemies attacking vineyard Coccidae than previously appreciated, although P. pruinosum may have few enemies.Significance of the StudyGrapevine scale pests have an array of natural enemies including parasitoids, beetles, moth larvae and lacewings, highlighting the importance of maintaining a diverse insect community in vineyards for biological control.
Australian Journal of Grape and Wine Research 04/2015; 21(2). DOI:10.1111/ajgw.12134 · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chromosomal inversion polymorphisms are common in animals and plants and recent models suggest that alternative arrangements spread by capturing different combinations of alleles acting additively or epistatically to favour local adaptation. It is also thought that inversions typically maintain favoured combinations for a long time by suppressing recombination between alternative chromosomal arrangements. Here, we consider patterns of linkage disequilibrium and genetic divergence in an old inversion polymorphism in Drosophila melanogaster (In(3R)Payne) known to be associated with climate change adaptation and a recent invasion event into Australia. We extracted, karyotyped and sequenced whole chromosomes from two Australian populations so that changes in the arrangement of the alleles between geographically separated tropical and temperate areas could be compared. Chromosome-wide linkage disequilibrium (LD) analysis revealed strong LD within the region spanned by In(3R)Payne. This genomic region also showed strong differentiation between the tropical and the temperate populations but no differentiation between different karyotypes from the same population, after controlling for chromosomal arrangement. Patterns of differentiation across the chromosome arm and in gene ontologies were enhanced by the presence of the inversion. These data support the notion that inversions are strongly selected by bringing together combinations of genes but it is still not clear if such combinations act additively or epistatically. Our data suggest that climatic adaptation through inversions can be dynamic, reflecting changes in the relative abundance of different forms of an inversion and ongoing evolution of allelic content within an inversion. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: AHTEENSUU ET AL. highlight four issues with our proposed framework for guiding decisions to conserve species under climate change and suggest some ways forward. From the outset we stress that we presented a framework. By their very nature, frameworks are for building on and elaborating. We thus welcome the contribution of Ahteensuu et al.. Here we continue the conversation about how the framework might more easily translate into practice across a range of applications.Issue 1: Yes/No answers are often not appropriateFirstly, the primary purpose of the framework we presented was to bring together (in one place) the suite of actions currently being considered to conserve species under climate change and begin the task of identifying constraints on the decision problem that might affect allocation of resources to particular actions. Candidate constraints included the likelihood of success, cost of implementation and likely co-benefits to non-target species (in addition to perceived vulner ...
[Show abstract][Hide abstract] ABSTRACT: The effects of climate change on biodiversity are increasingly well documented, and many methods have been developed to assess species' vulnerability to climatic changes, both ongoing and projected in the coming decades. To minimize global biodiversity losses, conservationists need to identify those species that are likely to be most vulnerable to the impacts of climate change. In this Review, we summarize different currencies used for assessing species' climate change vulnerability. We describe three main approaches used to derive these currencies (correlative, mechanistic and trait-based), and their associated data requirements, spatial and temporal scales of application and modelling methods. We identify strengths and weaknesses of the approaches and highlight the sources of uncertainty inherent in each method that limit projection reliability. Finally, we provide guidance for conservation practitioners in selecting the most appropriate approach(es) for their planning needs and highlight priority areas for further assessments.