Abstract
Quantifying the relative impact of environmental conditions and host community structure on disease is one of the greatest challenges of the 21st century, as both climate and biodiversity are changing at unprecedented rates. Both increasing temperature and shifting host communities toward more fast-paced life-history strategies are predicted to increase disease, yet their independent and interactive effects on disease in natural communities remain unknown. Here, we address this challenge by surveying foliar disease symptoms in 220, 0.5 m-diameter herbaceous plant communities along a 1100-m elevational gradient. We find that increasing temperature associated with lower elevation can increase disease by (1) relaxing constraints on parasite growth and reproduction, (2) determining which host species are present in a given location, and (3) strengthening the positive effect of host community pace-of-life on disease. These results provide the first field evidence, under natural conditions, that environmental gradients can alter how host community structure affects disease.
Highlights
Infectious disease is strongly influenced by host community structure and abiotic conditions (Halliday et al, 2020a; Halliday et al, 2019), both of which are undergoing unprecedented change as the climate is warming (Pachauri et al, 2014) and biodiversity is being reshuffled (Díaz et al, 2019; Hillebrand et al, 2018)
Our study reveals strong evidence that increasing temperature associated with lower elevation can directly influence disease risk, which we attribute to well-e stablished effects of abiotic conditions (Avenot et al, 2017; Garrett et al, 2006; Harvell et al, 2002; Tapsoba and Wilson, 1997; Waugh et al, 2003) on parasite replication and growth, and can indirectly influence disease risk by shifting host community structure and by modifying the trait-competence relationship
To evaluate abiotic constraints on parasite replication and growth, shifting host community structure, and modification of the trait- competence relationship as mechanisms through which environmental gradients can influence disease risk, we surveyed 220, 0.5 m-diameter vegetation communities, that were established in four meadows along a 1101 m elevational gradient as part of the Calanda Biodiversity Observatory (CBO) in 2019 in order to investigate biotic and abiotic drivers of species interactions (Figure 2; Supplementary file 1a)
Summary
Infectious disease is strongly influenced by host community structure and abiotic conditions (Halliday et al, 2020a; Halliday et al, 2019), both of which are undergoing unprecedented change as the climate is warming (Pachauri et al, 2014) and biodiversity is being reshuffled (Díaz et al, 2019; Hillebrand et al, 2018). In an experiment in the Rocky mountains, host plants that grew on heated research plots showed increased disease, largely by increasing the amount of time that environmental conditions were favorable for parasite growth and reproduction (Roy et al, 2004). These same environmental factors can indirectly influence disease risk by altering the composition of host or vector communities that are required for sustained parasite transmission
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