Host responses to historical climate change shape parasite communities in North America’s intermountain west

Authors: GALBREATH, KURT - Northern Michigan University; Hoberg, Eric

Submitted to: Folia Parasitologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2015
Publication Date: 10/20/2015
Citation: Galbreath, K.E., Hoberg, E.P. 2015. Host responses to historical climate change shape parasite communities in North America’s intermountain west. Folia Parasitologica. 64(3):218-232.

Interpretive Summary: Parasites represent an exceptionally diverse component of the biosphere yet the processes that produced this diversity are not fully understood. One concept of parasite diversification with deep roots in parasitology is that parasite lineages, especially those that are strongly host-specific, diverge as a direct consequence of host differentiation. This co-speciation model predicts that associated taxa speciate in concert, resulting in congruence in the histories between hosts and parasites. Such a clear phylogenetic prediction is relatively straightforward to test, and has consequences for understanding and predicting the ecological and evolutionary mechanisms involved in the assembly of the biosphere and in emerging diseases. Host-parasite co-speciation, in which parasite divergence occurs in response to host divergence, is commonly proposed as a driver of parasite diversification, yet few empirical examples of strict co-speciation exist. Host-parasite co-evolutionary histories commonly reflect complex mosaics of co-speciation, dispersal, and other phenomena. The episodic host-switching model of parasite diversification accounts for complexity by suggesting that diversification and faunal assembly is a consequence of fluctuations between environmental disruption and environmental stability. The historical phylogeographic (structure of populations based on genetic data) predictions of the strict co-speciation and episodic host-switching models were tested using the North American pika/parasite assemblage, with a primary focus on the American pika, Ochotona princeps (a small mammal related to hares and rabbits), and a suite of its endoparasitic tapeworms and roundworms. This approach integrating phylogeographic and demographic methods with inferences drawn from species distribution modelling revealed that the parasite community of pikas has been shaped by climate-driven range fluctuation of hosts and bouts of geographic and host colonization by parasites associated with transitions between glacial and interglacial phases. A significant conclusion, our studies have broader implications for understanding the nature of ecological and evolutionary mechanisms that determine the distribution of parasites and diseases. Emphasized here is a primary role for ecological disruption in leading to new distributions and associations of parasites over time, providing a powerful analogue for the outcomes of ongoing climate warming and environmental perturbation. Our results will be of interest and application to disease ecologists, environmental biologists, convservation biologists and managers in governmental and non-governmental agencies in exploring, anticipating and mitigating the impacts of environmental change over time.

Technical Abstract: Host-parasite co-speciation, in which parasite divergence occurs in response to host divergence, is commonly proposed as a driver of parasite diversification, yet few empirical examples of strict co-speciation exist. Host-parasite co-evolutionary histories commonly reflect complex mosaics of co-speciation, dispersal, lineage extinction and other phenomena. The episodic host-switching model of parasite diversification accounts for complexity by suggesting that diversification and faunal assembly is a consequence of oscillations between environmental disruption and environmental stability. The phylogeographic predictions of the strict co-speciation and episodic host-switching models were tested using the North American pika/parasite assemblage, with a primary focus on the American pika, Ochotona princeps (Richardson, 1828), and a suite of its endoparasitic cestodes and nematodes. This approach integrating phylogeographic and demographic methods with inferences drawn from species distribution modelling revealed that the parasite community of pikas has been shaped by climate-driven range fluctuation of hosts and bouts of geographic and host colonization by parasites associated with transitions between glacial and interglacial phases.