Modeling the potential distribution of the Ixodes pavlovskyi tick and its changes under current climatic conditions

The tick Ixodes pavlovskyi Pomerantsev, 1946 is a vector of tick-borne encephalitis virus, Borrelia, and a number of other diseases. It is widespread in Siberia and the Far East, and its range has expanded in recent decades. The purpose of this study was to create a model of its potential distribution over three periods: 1961–1980, 1981–2000 and 2001–2020, during which strong climate change was observed. Modeling was performed using the MaxEnt algorithm. A total of 81 detection points were identified from literature and databases. Bioclimatic parameters were used as the only predictors because climate is apparently the principal factor limiting the distribution of I. pavlovskyi. Five bioclimatic parameters with the lowest pairwise correlations and their transformation functions were selected to provide the best model. Akaike Information Criterion corrected (AICc), Boyce Index, and Area Under Curve (AUC) were used as model quality metrics. In addition to known distribution areas, new potential territories of distribution with high suitability were identified, including those in Russia, Japan, Central Asia, the Caucasus, China, Canada, and the northern United States. According to the results of modeling, the greatest changes in the potential climatic range of I. pavlovskyi during the study periods occurred in the Siberian part of its range, where the area of high suitability expanded substantially during 2001–2020 as a result of climate change. In other regions, little shift in the potential range of I. pavlovskyi was observed. Also, it was identified that BIO1 (annual mean temperature) and BIO15 (precipitation seasonality) are the most important parameters for model construction.