Predicting the potential distribution of Amblyomma americanum (Acari: Ixodidae) infestation in New Zealand, using maximum entropy-based ecological niche modelling.

Although currently exotic to New Zealand, the potential geographic distribution of Amblyomma americanum (L.), the lone star tick, was modelled using maximum entropy (MaxEnt). The MaxEnt model was calibrated across the native range of A. americanum in North America using present-day climatic conditions and occurrence data from museum collections. The resulting model was then projected onto New Zealand using both present-day and future climates modelled under two greenhouse gas emission scenarios, representative concentration pathways (RCP) 4.5 (low) and RCP 8.5 (high). Three sets of WorldClim bioclimatic variables were chosen using the jackknife method and tested in MaxEnt using different combinations of model feature class functions and regularization multiplier values. The preferred model was selected based on partial receiver operating characteristic tests, the omission rate and the lowest Akaike information criterion. The final model had four bioclimatic variables, Annual Mean Temperature (BIO1), Annual Precipitation (BIO12), Precipitation Seasonality (BIO15) and Precipitation of Driest Quarter (BIO17), and the projected New Zealand distribution was broadly similar to that of Haemaphysalis longicornis Neumann, New Zealand's only livestock tick, but with a more extensive predicted suitability. The climate change predictions for the year 2050 under both low and high RCP scenarios projected only moderate increases in habitat suitability along the mountain valleys in the South Island. In conclusion, this analysis shows that given the opportunity and license A. americanum could and would successfully establish in New Zealand and could provide another vector for theileriosis organisms.

Potential Spatial Distribution of the Newly Introduced Long-horned Tick, Haemaphysalis longicornis in North America.

The North American distributional potential of the recently invaded tick, Haemaphysalis longicornis, was estimated using occurrence data from its geographic range in other parts of the world and relevant climatic data sets. Several hundred candidate models were built using a correlative maximum entropy approach, and best-fitting models were selected based on statistical significance, predictive ability, and complexity. The median of the best-fitting models indicates a broad potential distribution for this species, but restricted to three sectors-the southeastern United States, the Pacific Northwest, and central and southern Mexico.

Ordinary stoichiometry of extraordinary microorganisms.

All life on Earth seems to be made of the same chemical elements in relatively conserved proportions (stoichiometry). Whether this stoichiometry is conserved in settings that differ radically in physicochemical conditions (extreme environments) from those commonly encountered elsewhere on the planet provides insight into possible stoichiometries for putative life beyond Earth. Here, we report measurements of elemental stoichiometry for extremophile microbes from hot springs of Yellowstone National Park (YNP). Phototrophic and chemotrophic microbes were collected in locations spanning large ranges of temperature (24 °C to boiling), pH (1.6-9.6), redox (0.1-7.2 mg L(-1) dissolved oxygen), and nutrient concentrations (0.01-0.25 mg L(-1) NO2-, 0.7-12.9 mg L(-1) NO3-, 0.01-42 mg L(-1) NH4 (+), 0.003-1.1 mg L(-1) P mostly as phosphate). Despite these extreme conditions, the microbial cells sampled had a major and trace element stoichiometry within the ranges commonly encountered for microbes living in the more moderate environments of lakes and surface oceans. The cells did have somewhat high C:P and N:P ratios that are consistent with phosphorus (P) limitation. Furthermore, chemotrophs and phototrophs had similar compositions with the exception of Mo content, which was enriched in cells derived from chemotrophic sites. Thus, despite the extraordinary physicochemical and biological diversity of YNP environments, life in these settings, in a stoichiometric sense, remains much the same as we know it elsewhere.

Interaction between lithification and resource availability in the microbialites of Río Mesquites, Cuatro Ciénegas, México.

Lithified microbial structures (microbialites) have been present on Earth for billions of years. Lithification may impose unique constraints on microbes. For instance, when CaCO3 forms, phosphate may be captured via coprecipitation and/or adsorption and potentially rendered unavailable for biological uptake. Therefore, the growth of microbes associated with CaCO3 may be phosphorus-limited. In this study, we compared the effects of resource addition on biogeochemical functions of microbial communities associated with microbialites and photoautotrophic microbial communities not associated with CaCO3 deposition in Río Mesquites, Cuatro Ciénegas, México. We also manipulated rates of CaCO3 deposition in microbialites to determine whether lithification reduces the bioavailability of phosphorus (P). We found that P additions significantly increased rates of gross primary production (F2,13 = 103.9, P < 0.001), net primary production (F2,13 = 129.6, P < 0.0001) and ecosystem respiration (F2,13 = 6.44, P < 0.05) in the microbialites, while P addition had no effect on photoautotrophic production in the non-CaCO3 -associated microbial communities. Growth of the non-CaCO3-associated phototrophs was only marginally stimulated when nitrogen and P were added simultaneously (F1,36 = 3.98, P = 0.053). In the microbialites, resource additions led to some shifts in the abundance of Proteobacteria, Bacteroidetes and Cyanobacteria but mostly had little effect on bacterial community composition. Ca(2+) uptake rates increased significantly with organic carbon additions (F1,13 = 8.02, P < 0.05). Lowering of CaCO3 deposition by decreasing calcium concentrations in the water led to increased microbial biomass accumulation rates in terms of both organic carbon (F4,48 = 5.23, P < 0.01) and P (F6,48 = 13.91, P < 0.001). These results provide strong evidence in support of a role of lithification in controlling P limitation of microbialite communities.

Community structure and biogeochemical impacts of microbial life on floating pumice.

Volcanic eruptions are a widespread force of geological and ecological disturbance and present recurrent opportunities for the study of biological responses to novel habitat formation. However, scientific study of such events is difficult given their short duration and often distant location. Here we report results from opportunistic sampling of unique volcano-generated habitats formed during the 2011 explosive eruption in the Puyehue-Cordón Caulle complex (Chile), when massive amounts of pumice were ejected, creating novel floating substrata that have never before been characterized from a microbiological perspective. DNA sequencing revealed a dynamic community of microbes that came to inhabit the pumice, with a unique composition distinct from that of the lakes' surface waters and with suggestions of ecological convergence across lakes and sampling times. Furthermore, biogeochemical studies of net nutrient fluxes showed that, while the fresh pumice arriving to the lakes was an initial source of phosphorus (P), colonized pumice had high rates of nitrogen (N) and P uptake and was sufficiently abundant to represent a significant lake-wide nutrient sink. These findings highlight the remarkable versatility of microbes in exploiting novel environments and are consistent with a recent proposal of floating pumice as a favorable environment for the initial origins of life on early Earth.

Ecological niche and potential geographic distribution of the invasive fruit fly Bactrocera invadens (Diptera, Tephritidae).

Two correlative approaches to the challenge of ecological niche modeling (genetic algorithm, maximum entropy) were used to estimate the potential global distribution of the invasive fruit fly, Bactrocera invadens, based on associations between known occurrence records and a set of environmental predictor variables. The two models yielded similar estimates, largely corresponding to Equatorial climate classes with high levels of precipitation. The maximum entropy approach was somewhat more conservative in its evaluation of suitability, depending on thresholds for presence/absence that are selected, largely excluding areas with distinct dry seasons; the genetic algorithm models, in contrast, indicate that climate class as partly suitable. Predictive tests based on independent distributional data indicate that model predictions are quite robust. Field observations in Benin and Tanzania confirm relationships between seasonal occurrences of this species and humidity and temperature.

Could the bug Triatoma sherlocki be vectoring Chagas disease in small mining communities in Bahia, Brazil?

Searches for Chagas disease vectors were performed at the type locality from which Triatoma sherlocki Papa et al. (Hemiptera: Reduviidae: Triatominae) was described in the municipality of Gentio do Ouro, in the state of Bahia, Brazil, and in a small artisan quarry-mining community approximately 13 km distant in a remote area of the same municipality. The latter site represents a new locality record for this species. Adults, nymphs and exuviae of T. sherlocki were found in 21% of human dwellings, indicating that the species is in the process of domiciliation. Prevalence of Trypanosoma cruzi infection in collected bugs was 10.8%. Simple predictive approaches based on environmental similarity were used to identify additional sites likely suitable for this species. The approach successfully predicted an additional five sites for the species in surrounding landscapes. Ecological and entomological indicators were combined to discuss whether this scenario likely represents an isolated case or an emerging public health problem.

Speciation in the highlands of Mexico: genetic and phenotypic divergence in the Mexican jay (Aphelocoma ultramarina).

The pine-oak woodlands of the Mexican highlands harbour significant biological diversity, yet little is known about the evolutionary history of organisms inhabiting this region. We assessed genetic and phenotypic differentiation in 482 individuals representing 27 populations of the Mexican jay (Aphelocoma ultramarina) - a widespread bird species of the Mexican highlands - to test whether populations in the central and northern Mexican sierras display discrete breaks between groups, which would be consistent with a role for the different mountain chains in divergence and speciation. We found abrupt breaks in mitochondrial DNA (mtDNA; ND2 and control region) delineating four major genetic groups found in the Sierra Madre Occidental, Sierra Madre Oriental, southern Central Plateau (Bajio), and Transvolcanic Belt. These mtDNA groups were largely corroborated by data from nuclear microsatellites and phenotypic data, except that clades from the Central Plateau and Sierra Madre Oriental showed clinal change in these data sets. Uncertainty about the mutation rate for our mitochondrial markers warrants considerable caution with regard to estimating divergence times, but the major genetic groups appear to have split before the most extreme period of glacial cycling that marked the last 0.7 million years and after Mexico's period of major mountain formation. The fact that some genetic breaks do not coincide with well-known geographic barriers suggests a role for ecology in divergence and speciation, and we discuss implications for taxonomy and conservation.

Evidence of climatic niche shift during biological invasion.

Niche-based models calibrated in the native range by relating species observations to climatic variables are commonly used to predict the potential spatial extent of species' invasion. This climate matching approach relies on the assumption that invasive species conserve their climatic niche in the invaded ranges. We test this assumption by analysing the climatic niche spaces of Spotted Knapweed in western North America and Europe. We show with robust cross-continental data that a shift of the observed climatic niche occurred between native and non-native ranges, providing the first empirical evidence that an invasive species can occupy climatically distinct niche spaces following its introduction into a new area. The models fail to predict the current invaded distribution, but correctly predict areas of introduction. Climate matching is thus a useful approach to identify areas at risk of introduction and establishment of newly or not-yet-introduced neophytes, but may not predict the full extent of invasions.

Environmental factors associated with distribution and range limits of malaria vector Anopheles farauti in Australia.

Ecological factors associated with the narrow coastal distribution of Anopheles farauti Laveran s.s. were investigated using decision tree software and a recently developed software tool that permits analysis of environmental gradients across distributional boundaries. Significant variables identified by these procedures were then used to develop ecological niche models that permitted detailed--and improved--predictions of the species' overall distribution. These methods identified seven climatic factors (four of temperature factors and three atmospheric moisture factors) from among 40 environmental variables related to the range of this species. In addition, the gradient-analysis tool identified elevation as being particularly important. The distributional hypothesis predicted using ecological niche modeling of these factors included all of the record sites from which An. farauti s.s. was collected in northern Australia and successfully reconstructed its narrow limitation to coastal areas. Omission of elevation from analyses resulted in unrealistic predictions of potential distributional areas > 100 km inland, where the species has not been found.

Metabolic responses associated with deer hunting.

PURPOSE: Deer hunting is a popular recreational activity with a high rate of cardiovascular events. Previous studies have demonstrated large HR responses during deer hunting. This study compared the HR and metabolic costs of maximal treadmill (TM) exercise with those of hiking while deer hunting and while dragging a deer. METHODS: Healthy male volunteers (N = 16) performed a maximal TM exercise test, a 0.8-km hiking test, and a 0.4-km dragging test over lightly rolling terrain. VO2 was measured by portable spirometry and HR by radiotelemetry. RESULTS: HR averaged 74.0 +/- 7.0% and 89.1 +/- 4.5% of peak TM HR during the hike and drag, respectively. The peak HR observed during hiking and dragging was 83.2 +/- 6.0% and 94.9 +/- 4.2% of peak TM HR, respectively. VO2 averaged 62.2 +/- 15.8% and achieved a peak of 77.2 +/- 19.0% of TM VO2 while hiking. This corresponded to 86.8 +/- 17.3% and 108.1 +/- 22.3% of ventilatory threshold (VT), respectively. VO2 averaged 72.3 +/- 21.0% and achieved a peak of 91.2 +/- 21.4% of peak TM VO2 while dragging the deer. This corresponded to 101.5 +/- 27.7% and 128.5 +/- 26.8% of VT, respectively. The VO2/HR relationship showed significant (P < 0.05) difference between the dragging test and the TM test with a disproportionately high HR. The VO2/HR relationship between the hiking and TM tests was comparable. CONCLUSION: In part, the previously described large HR responses and high rate of cardiovascular complications associated with deer hunting may attributable to the elevated metabolic costs of associated activities.