Viruses are the most abundant life form on Earth, but there are significant gaps in our understanding of the diversity, distribution and consequences of virus infection in wild hosts. Plant viruses are particularly poorly characterized in native perennial host species, but recent technological advancements have enabled de novo study of various viruses across diverse plant taxa. We use metagenomic methods to assess the diversity of leaf-associated viruses infecting the wild host Boechera stricta across Gothic Valley in south-central Colorado. The theoretical foundation of this research is grounded in classical biogeographical hypotheses that predict diversity will decrease as environmental conditions become increasingly stressful. In particular, abiotic conditions across elevational clines often, though not always, predict monotonically linear decrease in species diversity for many taxonomic groups. In this framework, we would expect plant viruses to be more diverse and abundant at low elevation, and to become rarer at higher elevation. Here we use RNA sequencing of field-collected plant virome samples to answer the motivating question: does plant virus diversity vary across an elevation cline?
Results/Conclusions
Virus diversity was negatively correlated with elevation across the five host populations included in this study. Using metagenomic methods, we show that sampling at the biological scale of host populations is adequate to assess virus taxonomic diversity across an elevation cline. Finally, we show that differences in virus diversity are generally greater between host populations than within. Results of this study indicate that spatial distributions of plant viruses vary with abiotic conditions, and the loss of virus taxa at high elevation sites may represent an upslope range edge. Further studies are needed to determine if this potential edge is the result of dispersal limitation, host environmental conditions or population-level host genetic differences. Characterizing plant virus distributions is important given the likelihood of migration of hosts and insect vectors. It is likely that rapid climate change in alpine environments will facilitate upslope range expansions for viruses, and may increase the likelihood of pathogen emergence in naive host species or populations.
