Ecological consequences of parasite host shifts under changing environments: more than a change of partner

(1) Parasitic plants, among many other parasitic organisms, are shifting in their geographic distribution in response to global change, establishing novel interactions with susceptible but previously unexposed host plants. Projections of future species assemblages in increasingly changing environments frequently overlook the strong capacity of these parasites to transform ecological systems, and host switching is considered a mere change of partner with no subsequent impact on ecosystem properties. (2) We explore the ecological consequences of parasite host shifts analysing the growth and reproductive responses of two host trees that share a different interaction-history with the parasitic plant Viscum album: recent in the case of Pinus sylvestris subsp. nevadensis and longstanding in that of Pinus nigra. We quantified growth by measuring primary (bud elongation) and secondary (dendrochronology) tree growth, and reproduction by quantifying cone crops, cone size, seed production, seed...