Methodological caveats in the environmental modelling and projections of climate niche for ticks, with examples for Ixodes ricinus (Ixodidae)

Estrada-Peña, Agustı́n; Estrada-Sánchez, Adrián; Estrada-Sánchez, David

doi:10.1016/j.vetpar.2014.12.016

Cited by 31 publications

(34 citation statements)

References 98 publications

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“…Uncertainties appeared in the modelling process, especially in the selection of explanatory variables. As suggested by experts [ 4 ], only biologically meaningful variables were considered instead of the frequently applied approach of reducing significant variables from a large set of possible explanatory variables. As a side effect, collinearities (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…As a side effect, collinearities (e.g. between altitude and temperature) were estimated, which should be avoided in generally applicable models [ 4 ]. Due to the low number of explanatory variables used in the model, this is, however, not possible without reducing the model’s performance.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, various statistical models to describe species habitats have been developed. An overview on models as well as methodological caveats in the modelling with examples for I. ricinus was described by Estrada-Peña and co-authors [ 4 ]. Several applications focus on the projection of climate niche models to estimate future scenarios.…”

Section: Introductionmentioning

confidence: 99%

“…Several applications focus on the projection of climate niche models to estimate future scenarios. These studies provide maps of suitability indices and presence/absence maps of both the present and the future distribution of I. ricinus , covering Europe and Northern Africa [ 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

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Estimating Ixodes ricinus densities on the landscape scale

et al. 2015

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BackgroundThe study describes the estimation of the spatial distribution of questing nymphal tick densities by investigating Ixodes ricinus in Southwest Germany as an example. The production of high-resolution maps of questing tick densities is an important key to quantify the risk of tick-borne diseases. Previous I. ricinus maps were based on quantitative as well as semi-quantitative categorisations of the tick density observed at study sites with different vegetation types or indices, all compiled on local scales. Here, a quantitative approach on the landscape scale is introduced.MethodsDuring 2 years, 2013 and 2014, host-seeking ticks were collected each month at 25 sampling sites by flagging an area of 100 square meters. All tick stages were identified to species level to select nymphal ticks of I. ricinus, which were used to develop and calibrate Poisson regression models. The environmental variables height above sea level, temperature, relative humidity, saturation deficit and land cover classification were used as explanatory variables.ResultsThe number of flagged nymphal tick densities range from zero (mountain site) to more than 1,000 nymphs/100 m2. Calibrating the Poisson regression models with these nymphal densities results in an explained variance of 72 % and a prediction error of 110 nymphs/100 m2 in 2013. Generally, nymphal densities (maximum 374 nymphs/100 m2), explained variance (46 %) and prediction error (61 nymphs/100 m2) were lower in 2014. The models were used to compile high-resolution maps with 0.5 km2 grid size for the study region of the German federal state Baden-Württemberg. The accuracy of the mapped tick densities was investigated by leave-one-out cross-validation resulting in root-mean-square-errors of 227 nymphs/100 m2 for 2013 and 104 nymphs/100 m2 for 2014.ConclusionsThe methodology introduced here may be applied to further tick species or extended to other study regions. Finally, the study is a first step towards the spatial estimation of tick-borne diseases in Central Europe.Electronic supplementary materialThe online version of this article (doi:10.1186/s12942-015-0015-7) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimating Ixodes ricinus densities on the landscape scale

et al. 2015

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“…All presence data for each tick species were used to train the models for projection in current and future climates. This ensured that the maximum amount of information on the current climate niche of the species was available to the model [ 54 , 55 ]. Climate suitability maps are presented as averages of Maxent and MD outputs.…”

Section: Methodsmentioning

confidence: 99%

Climate suitability for European ticks: assessing species distribution models against null models and projection under AR5 climate

et al. 2015

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BackgroundThere is increasing evidence that the geographic distribution of tick species is changing. Whilst correlative Species Distribution Models (SDMs) have been used to predict areas that are potentially suitable for ticks, models have often been assessed without due consideration for spatial patterns in the data that may inflate the influence of predictor variables on species distributions. This study used null models to rigorously evaluate the role of climate and the potential for climate change to affect future climate suitability for eight European tick species, including several important disease vectors.MethodsWe undertook a comparative assessment of the performance of Maxent and Mahalanobis Distance SDMs based on observed data against those of null models based on null species distributions or null climate data. This enabled the identification of species whose distributions demonstrate a significant association with climate variables. Latest generation (AR5) climate projections were subsequently used to project future climate suitability under four Representative Concentration Pathways (RCPs).ResultsSeven out of eight tick species exhibited strong climatic signals within their observed distributions. Future projections intimate varying degrees of northward shift in climate suitability for these tick species, with the greatest shifts forecasted under the most extreme RCPs. Despite the high performance measure obtained for the observed model of Hyalomma lusitanicum, it did not perform significantly better than null models; this may result from the effects of non-climatic factors on its distribution.ConclusionsBy comparing observed SDMs with null models, our results allow confidence that we have identified climate signals in tick distributions that are not simply a consequence of spatial patterns in the data. Observed climate-driven SDMs for seven out of eight species performed significantly better than null models, demonstrating the vulnerability of these tick species to the effects of climate change in the future.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1046-4) contains supplementary material, which is available to authorized users.

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The ecological niche of Dermacentor marginatus in Germany

2016

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The ixodid tick Dermacentor marginatus (Sulzer, 1776) is endemic throughout southern Europe in the range of 33–51 ° N latitude. In Germany, however, D. marginatus was exclusively reported in the Rhine valley and adjacent areas. Its northern distribution limit near Giessen is located at the coordinates 8.32 ° E/50.65 ° N. Particularly with regard to the causative agents of rickettsioses, tularemia, and Q fever, the observed locations as well as the potential distribution of the vector D. marginatus in Germany are of special interest. Applying a dataset of 118 georeferenced tick locations, the ecological niche for D. marginatus was calculated. It is described by six climate parameters based on temperature and relative humidity and another six environmental parameters including land cover classes and altitude. The final ecological niche is determined by the frequency distributions of these 12 parameters at the tick locations. Main parameters are the mean annual temperature (frequency distribution characterized by the minimum, median, and maximum of 6.1, 9.9, and 12.2 °C), the mean annual relative humidity (73.7, 76.7, and 80.9 %), as well as the altitude (87, 240, 1108 m). The climate and environmental niche is used to estimate the habitat suitability of D. marginatus in Germany by applying the BIOCLIM model. Finally, the potential spatial distribution of D. marginatus was calculated and mapped by determining an optimal threshold value of the suitability index, i.e., the maximum of sensitivity and specificity (Youden index). The model performance is expressed by AUC = 0.91.

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Methodological caveats in the environmental modelling and projections of climate niche for ticks, with examples for Ixodes ricinus (Ixodidae)

Cited by 31 publications

References 98 publications

Estimating Ixodes ricinus densities on the landscape scale

Estimating Ixodes ricinus densities on the landscape scale

Climate suitability for European ticks: assessing species distribution models against null models and projection under AR5 climate

The ecological niche of Dermacentor marginatus in Germany

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