Survival in the Understorey: Unravelling Direct and Indirect Effects of Microclimatological Changes on Ixodes Ricinus

Abstract

The distribution of ticks in the Ixodes ricinus species complex is partly driven by climate, with temperature and relative humidity affecting survival. These variables are driven by macroclimate, but vary locally due to microclimate buffering. This buffering has been suggested to be the driving force behind variation in tick survival and density in time and space. In order to understand the role of herb the herb layer vegetation with respect to this variation, we deployed Ixodes ricinus within an existing experimental setup studying the response of forest understorey to micrometeorological changes. This allowed for the analysis of both direct effects of warming on tick survival in controlled field conditions, as well as indirect effects through changes in herb layer biomass. Both tick survival and herb layer biomass estimates were observed to be higher in plots that had been experimentally warmed. Although, for the former, effect sizes were small. The marginal increase in survival rate may be due to increased microclimate buffering. Comparing our results to literature implies that canopy and shrub layer vegetation have a larger effect on climate buffering, and therefore also on tick survival. Since the herb layer biomass is expected to increase due to global warming and increased frequency of disturbance-induced canopy gaps, survival in forested habitats may increase in the future. This would increase the difference in survival compared to that in open habitats.

Keywords: Ixodes ricinus, Ectoparasites, Survival, Global Warming, Microclimate Buffering