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Using ground-derived data to assess the environmental niche of the spinose ear tick, Otobius megnini


Correspondence: Agustín Estrada-Peña, Department of Parasitology, Faculty of Veterinary Medicine, Miguel Servet 177, 50013-Zaragoza, Spain. E-mail:


Four layers of environmental information, namely 1) monthly atmospheric temperature and rainfall, 2) annual ground and underground moisture, evaporation, surface adjacent specific humidity, and temperature, 3) monthly Normalized Derived Vegetation Index (NDVI), and 4) soil physical attributes, were used separately to define the expected geographical distribution and environmental niche of the spinose ear tick, Otobius megnini (Dugès) (Acari: Ixodida: Argasidae), an endophilic argasid, in both tropical and neotropical regions. The best predictive values were obtained from ground-derived climate. Air-derived features ranked second. The remaining environmental information had poor discriminatory abilities. The most informative variables in the distribution of neotropical populations are ground temperatures, with surface humidity ranking second. In the tropics, surface humidity is the most important factor delineating the distribution of O. megnini. Marginality scores are similar for tick populations in both biogeographical regions, but specialization factors are different, supporting the findings that both populations are regulated by different variables. Similarly, models trained with records of one biogeographical region and projected into the other one, resulted in poorer predictions than when trained with the homologous set of records. Populations of the tick in the tropics experience a different range of temperatures than their neotropical relatives, whereas marginality scores are similar. The conclusion is that each population uses particular portions of the environmental niche, probably because of different climate or competitor constraints on either biogeographical region.