Host specificity by parasites is hypothesized to be a critical determinant of disease dynamics. Parasite traits mediating host specificity can show exceptional intraspecific variation, but we know little regarding how specialization of individual parasites or populations scales up to continent level processes. Additionally, in ecology it is often unknown whether the distributions of organisms across environments actually correspond to preferred environments. Here, we develop a macroecological framework for mapping geographic regions with increased likelihood of host-specialized parasite populations, based on comparisons of environmental niche models built from subsets of occurrence data on different hosts. We test our approach using natural history collections of Striga hermonthica, a root parasitic plant that infests maize, millet, sorghum, and rice and constitutes a major constraint to global food security.
Results/Conclusions
For native African crops sorghum and pearl millet we find strong concordance between model predictions and observations of host specialization from previous empirical studies. Continent-scale datasets describing distribution of host cereals enable further validation of predictions from our model. Projections to future climate scenarios suggest increased habitat suitability for S. hermonthica overall by the year 2050 and predict an increased vulnerability of pearl millet to S. hermonthica. Our study demonstrates the utility of environmental niche model contrasts for predicting host-specialized populations of parasites at broad scale.