Amblyomma mixtumfree-living stages: Summer and winter use, preference, and niche width in an agroecosystem (Yopal, Casanare, Colombia)

Abstract

Studying a species’ tolerance to an ecosystem’s environmental conditions and its selection of available resources is relevant in ecological and evolutionary terms. Moreover, formulation of effective control strategies implicitly includes the study of habitat use and preference and niche width in anthropogenically transformed natural landscapes. Here, we evaluated whether the use, habitat preference, and niche range of the Amblyomma mixtum tick changed between stages, habitats, and seasons (summer-winter 2019) on a farm in Yopal (Casanare, Colombia). To this end, the presence and relative abundance of larvae, nymphs, and free-living adults was quantified in four different habitats according to the type of vegetation cover (Riparian Forest, Cocoa Crop, King Grass Crop, and Star Grass Paddock). Habitat availability was calculated, environmental variables were analyzed, and various indices of habitat use and preference and niche width were calculated. A. mixtum’s habitat use and preference and niche width changed between stages, habitat types, and time of the year. The total abundance of A. mixtum was an order of magnitude greater in summer than winter. Nymphs and larvae dominated it in the summer and adults in the winter. In summer, all the stages used the four habitats. In winter, the larvae did not use two habitats (Riparian Forest and Cocoa Crop); nymphs did not use the cocoa crop. A. mixtum adults used all the habitats in both seasons. In summer, the nymphs and larvae preferred three of the four habitats (King Grass Crop, Star Grass Paddock, and Cocoa Crops), while adults preferred the King Grass Crop. In winter, the nymphs and larvae preferred the King Grass Crop and Star Grass Paddock, while the adults preferred the King Grass Crop. The value of the niche width index was high for larvae, nymphs, and adults in summer, while it was high only for adults in winter. A. mixtum is exposed to significant daily, seasonal, and multiannual variations in relative humidity (minimum 30%), ambient temperature (minimum 18°C), solar radiation (maximum 800 W/m2), and precipitation (maximum 481 mm/month). Thus, the local A. mixtum population could rapidly acclimatize to changing habitats (unstable or temporary) under fluctuating environmental conditions (e.g., King Grass Crop). However, the winter flood season in Yopal could exceed A. mixtum’s adaptive capacity during its most vulnerable stages. Mathematically, a low number of female A. mixtum, surviving the most demanding environmental conditions, could sufficiently ensure the population’s persistence, which, coupled with the vast host range, could facilitate the ticks stages’ dispersal among habitats to complete their life cycle. A. mixtum’s population control should be carried out during its season of greater vulnerability (winter), when the population is low, particularly the females.