Abstract
A growing body of research is focused on the extinction of parasite species in response to host endangerment and declines. Beyond the loss of parasite species richness, host extinction can impact apparent parasite host specificity, as measured by host richness or the phylogenetic distances among hosts. Such impacts on the distribution of parasites across the host phylogeny can have knock-on effects that may reshape the adaptation of both hosts and parasites, ultimately shifting the evolutionary landscape underlying the potential for emergence and the evolution of virulence across hosts. Here, we examine how the reshaping of host phylogenies through extinction may impact the host specificity of parasites, and offer examples from historical extinctions, present-day endangerment, and future projections of biodiversity loss. We suggest that an improved understanding of the impact of host extinction on contemporary host–parasite interactions may shed light on core aspects of disease ecology, including comparative studies of host specificity, virulence evolution in multi-host parasite systems, and future trajectories for host and parasite biodiversity.This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.
Highlights
The Earth’s biodiversity is in the midst of a crisis, with current rates of extinction that are conservatively 100 times faster than the normal background rate [1]
While current coextinction theory largely addresses parasite extinction resulting from host extinction, we suggest that expanding this framework to include contemporary measures of host specificity and theory underlying co-adaptation and virulence evolution in multi-host systems will be crucial to understanding how biodiversity loss impacts infectious diseases more broadly
There are 352 documented mammal extinctions, which resulted in evolutionary distinctiveness (ED) shifts for 551 extant mammals. The majority of these ED gains are less than 1 million years, but some species have seen large gains in ED on the order of tens of millions of years of added distinctiveness. As these hosts have lost close relatives, we suggest that the impacts of historical host extinction on parasite host specificity may be gleaned from investigating the ecology and evolution of parasites surviving on them
Summary
The Earth’s biodiversity is in the midst of a crisis, with current rates of extinction that are conservatively 100 times faster than the normal background rate [1]. Host extinction has the potential to result in parasite extinction, but may alter host specificity and shift the evolutionary landscapes shaping future parasite evolution. Identifying the set of host species that a parasite could infect given suitable opportunity (i.e. the potential host range of a parasite) allows us to infer ancestral host–parasite associations [29] and make crucial predictions of the potential for emergence in novel hosts [30,31] and likely impacts following cross-species transmission [32,33,34]. While current coextinction theory largely addresses parasite extinction resulting from host extinction, we suggest that expanding this framework to include contemporary measures of host specificity and theory underlying co-adaptation and virulence evolution in multi-host systems will be crucial to understanding how biodiversity loss impacts infectious diseases more broadly
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
