Data for: Off-host survival of blacklegged ticks in eastern North America: A multi-stage, multi-year, and multi-site study

Climatic conditions are widely thought to govern the distribution and abundance of ectoparasites, such as the blacklegged tick (Ixodes scapularis), vector of the agents of Lyme disease and other emerging human pathogens. However, translating physiological tolerances to distributional limits or mortality is challenging. Ticks may be able to avoid or tolerate unsuitable conditions, and what is lethal to one life history stage may not extend to others. Thus, even after decades of research there are clear gaps in our knowledge about how climatic conditions determine tick distributions or patterns of abundance. We present the results of a comprehensive, three-year study of the influence of local temperatures and vapor pressure deficits on the survival of each free-living, off-host stage of I. scapularis in semi-natural enclosures across three locations that span their current distribution in eastern North America. We found that only larvae are clearly sensitive to direct mortality from climatic conditions, specifically desiccating conditions, whereas mortality of nymphs and adults appears to stem from exhausted energy reserves. We also found strong evidence that key developmental transitions in the tick’s life cycle—fed larvae molting into to nymphs, fed nymphs molting into adults, and fed females producing larvae (via egg masses)—were all strongly temperature-dependent, though temperatures were not limiting in any of our sites. Collectively, our results suggest that climate is likely to impact I. scapularis largely through its impact on the larval stage.

Methods
Primary data consists of known numbers of ticks of a given life stage deployed in soil core enclosures (SCEs) and then the number recovered alive at a later date. This includes all flat (unfed) tick life stages as well as recently fed ticks molting (fed larvae and fed nymphs) or producing offspring (fed adults). These survivorship and life history transition data are paired with data on the daily ambient conditions (temperature and vapor pressure deficit) averaged across the roughly hourly readings of numerous iButton data loggers.