Data from: Disease from leaves to landscapes: Viral hotspots are determined by spatial arrangement and phytochemistry of host plants in specialist caterpillars

Although infectious diseases play a critical role in population
regulation, the drivers of disease prevalence in insects have most often
been investigated in isolation, thus our knowledge of disease dynamics for
insects is severely limited. We conducted a field study on Baltimore
checkerspots (Euphydryas phaeton) to investigate the roles of host plants,
phytochemistry, ontogeny, and larval spatial associations in determining
viral prevalence at the landscape scale. We analyzed individuals for viral
presence and loads, and quantified secondary phytochemistry from their
native and novel host plants. We found caterpillar groups that were more
proximate had greater similarity in infection prevalence, with areas of
high prevalence indicating the presence of viral hotspots. Post-diapause
caterpillars had higher infection rates than other developmental stages.
We found that infection prevalence was linked to phytochemistry for both
plants; infection prevalence was similar on both host plants at low
phytochemical concentrations but diverged at high concentrations with the
native plant showing low prevalence and the exotic plant hosting high
prevalence. Altogether, our findings reveal that spatial proximity,
ontogeny, larval host plant species, and phytochemistry are important in
structuring infection risk and thus offer insight into causal drivers of
disease prevalence in complex plant-insect systems.