Maximum Entropy-Based Ecological Niche Model and Bio-Climatic Determinants of Lone Star Tick (Amblyomma americanum) Niche

Abstract

The potential distribution of Amblyomma americanum ticks in Kansas was modeled using maximum entropy (MaxEnt) approaches based on museum and field-collected species occurrence data. Various bioclimatic variables were used in the model as potentially influential factors affecting the A. americanum niche. Following reduction of dimensionality among predictor variables using principal components analysis, which revealed that the first two principal axes explain over 87% of the variance, the model indicated that suitable conditions for this medically important tick species cover a larger area in Kansas than currently believed. Soil moisture, temperature, and precipitation were highly correlated with the first two principal components and were influential factors in the A. americanum ecological niche. Assuming that the niche estimated in this study covers the occupied distribution, which needs to be further confirmed by systematic surveys, human exposure to this known disease vector may be considerably under-appreciated in the state.

Keywords: Amblyomma americanum; Climate; Lone star tick; MaxEnt; Precipitation; Soil moisture; Temperature.

FIG. 1.

Abiotically suitable regions for A. americanum ticks in Kansas as modeled with MaxEnt.

FIG. 2.

County-level presence map of A. americanum ticks in Kansas. Shaded counties include one or multiple locations where nymph, larvae, and adult stages of A. americanum were recorded by one or more presence data source in this study—the Walter Reed Biosystematics Unit, the Prairie Arthropod Research at Kansas State University, and field collections conducted between years 2012 and 2014.