Negative spatial covariation in abundance of two European ticks: diverging niche preferences or biotic interaction?

Abstract

1. Understanding the ecological niches of ticks is central to predicting the risk of tick‐borne disease occurrence. Despite considerable advances in describing species distributions over the last two decades, disentangling the differences in habitat preferences from biotic interactions still remains among the main challenges.2. In boundary areas along the rivers Danube, Morava and Dyje, separating the Czech Republic, Slovakia and Austria, we studied ecological niche segregation between two European sympatric tick species, Dermacentor reticulatus and Ixodes ricinus, the abundances of which exhibited a negative spatial covariation. By applying ANCOVA analysis, we tested the effects of 19 climate, four moisture and two topographical variables derived through GIS on tick abundances.3. Dermacentor reticulatus preferred warmer and wetter sites with greater diurnal and seasonal variation in temperature but with lower seasonality in precipitation than I. ricinus.4. By adopting the static regression model based on a modified Lotka–Volterra model for interspecific competition, we examined the relative power of environmental variables to explain the negative relationship between tick log‐abundances. We found that nonzero estimates of competition coefficients α12 and α21 were not eliminated even if we included seven principal components derived from considered environmental variables.5. These results suggest that habitat conditions can shape abundance patterns of the studied ticks but their overall power to explain negative spatial covariation is low. This indicates that other critical variables were not considered in the analysis. An alternative explanation suggests that competitive interaction is not yet supported by direct field evidence obtained for these ticks.