Using invaded range data to model the climate suitability for Amblyomma variegatum (Acari: Ixodidae) in the New World

Abstract

Climate matching models are in increasing use to predict distributions of living organisms, using records of the known distribution of a species to map its expected range of habitat suitability. Here, we modelled the known distribution of the tick Amblyomma variegatum in Africa as a preliminary step to delineate the most probable range of climatically suitable habitat for the tick in the New World. We used two presence-only methods (one based in the Gower distance, the other based on the Maximum Entropy principle) to model the distribution range in Africa. The Maximum Entropy method is highly dependent of the realized niche of the tick, and has serious constraints in the case of lack of adequate description of the actual range of the tick. The Gower distance, however, can evaluate the fundamental niche of the tick and produced better results with the same set of distribution data. Several populations of A. variegatum were recognized in Africa on the basis of statistically different ecological attributes. The separate modelling of the climate envelope for these populations provided a better fit in the delineation of habitat suitability with both methods in Africa but produced high rates of false negatives when applied to the Caribbean. The best modelling strategy for the tick in the New World (according to the rate of false negatives) is the use of Gower distance together with the known distribution of the tick in the Caribbean. The potential spread area of the tick includes all the Caribbean, large areas of Colombia and Venezuela, parts of Brazil, most of the Mesoamerican corridor and Mexico as well as the Peninsula of Florida. We do not consider further if the invading strain either still retains the full ecological plasticity of the original populations in Africa, or has already adapted to the invaded area, resulting in a more restricted ability to expand. Both possibilities have deep impact in our analyses, as the tick could find a larger zone for spreading into the New World.