Environmental differentiation between the invasive cattle fever ticks Rhipicephalus (Boophilus) microplus and Rhipicephalus (Boophilus) annulatus revealed by comparative geographical ecology.

Cattle fever ticks, Rhipicephalus (Boophilus) microplus and R. (B.) annulatus, are major constraints on cattle production worldwide because they directly reduce productivity and transmit the agents of bovine babesiosis and anaplasmosis. Despite their shared hosts and similar vector capacity, their environmental preferences and the extent to which they occupy comparable climatic space remain unclear. We compiled historical occurrence records from global sources and, after quality control and spatial thinning, retained 2338 records for R. (B.) microplus and 527 for R. (B.) annulatus. Using climate, vegetation and soil variables, we characterized occupied environments, reconstructed geographically accessible areas with dispersal simulations, and compared climatic niches using methods that approximate fundamental and realized components. Both species were recorded across all major terrestrial biomes except tundra and in all livestock production systems. Environmental profiles nevertheless differed significantly: R. (B.) microplus occurred more often in warmer, wetter and more vegetated settings with moister soils and more stable surface temperatures, whereas R. (B.) annulatus was more frequently associated with drier environments and a broader range of thermal extremes. Climatic niche similarity was low to moderate and was statistically supported mainly for temperature-based niches. These results indicate that cattle fever ticks are not as environmentally distinct as often assumed, but they differ in how they partition environmental space. This information complements existing knowledge about the ecology and distribution of cattle fever ticks and motivate testable hypotheses about species interactions.