Are we more ignorant than interactions are relevant? Case examples from human disease and carnivore parasites

Background/Question/Methods Evidence from previous climate change events suggest that species move in response to changing climate in ways more complex than would be suspected on the basis of models that assume species simply track climate. One possible explanation for these deviations is that species tend to be dispersal limited. Another possibility, however, is that they require not only appropriate climate but also appropriate hosts or partners. Here we use data from global disease databases and a regional database of carnivore hosts and their parasites to examine how dependent species, such as parasites or commensals, are likely to shift given different assumptions about how directly climate influences them.
Results/Conclusions

The diversity of parasites and commensals under warmer climates appears most strongly influenced by the effects of climate on host distributions. Knowing host distributions under future climates serves as a reasonable proxy for future diversity patterns of parasites and commensals. The abundance (or prevalence) of parasites and commensals on the other hand is much more difficult to predict and may in fact be impossible to predict, given that abundance is most influenced by factors at local scales at which general climate models predictions are the least reliable and idiosyncratic human actions carry the most weight.