Abstract
Future climate change has the potential to alter the distribution and prevalence of plant pathogens, which may have significant implications for both agricultural crops and natural plant communities. However, there are few long-term datasets against which modelled predictions of pathogen responses to climate change can be tested. Here, we use 18S metabarcoding of 28 rodent middens (solidified deposits of rodent coprolites and nesting material) from the Central Atacama, spanning the last ca. 49 ka, to provide the first long-term late Quaternary record of change in plant pathogen communities in response to changing climate. Plant pathogen richness was significantly greater in middens deposited during the Central Andean Pluvial Event (CAPE); a period of increased precipitation between 17.5–8.5 ka. Moreover, the occurrence frequency of Pucciniaceae (rust fungi) was significantly greater during the CAPE, and the highest relative abundances for five additional potentially pathogenic taxa also occurred during this period. The results demonstrate the promising potential for ancient DNA analysis of late Quaternary samples to reveal insights into how plant pathogens responded to past climatic and environmental change, which could help predict how pathogens may responded to future change.
Highlights
Herbaria collections have been recognised as one potential resource for studying temporal dynamics in plant pathogen populations[18,19], but are limited to just the last few hundred years
Three were oomycetes genera: Albugo (100% identity to Albugo spp., nearest 94%), Hyaloperonospora (100–98% identity to Hyaloperonospora, nearest 94%) and Pythium (100% identity to Pythium spp., other Pythium spp. 96% and lower), and three were fungal: Pucciniaceae, or rust fungi (100% identity only to taxa within this family), Ustilaginomycotina, or smut fungi and Fusarium culmorum (100% identity, other Fusarium spp. have mismatches)
Three additional fungal taxa identified from the middens include high proportions of plant pathogenic species: Phytophthora (98–96% identity to some Phytophthora spp., other P. spp. and genera lower), Colletotrichum (98% identity to Colletotrichum, closest 95%) and Dothideomycetes (100% identities dominated by pathogenic taxa within Capnodiales, Mycosphaerellaceae, and Botryosphaeriaceae)
Summary
Herbaria collections have been recognised as one potential resource for studying temporal dynamics in plant pathogen populations[18,19], but are limited to just the last few hundred years. Late Quaternary palaeoecological records, extending over the past several millenia, provide an alternative option for gaining a longer-term view Such records have revealed clues about the responses of many different organisms during past large-scale environmental and climate change events e.g.20–22. Plant pathogens are phylogeneticaly diverse (including viruses, bacteria and eukaryotes) and leave little evidence in terms of the proxies conventionally used in late Quaternary palaeoecology (e.g. microscopic plant and invertebrate remains)[23]. Increases in precipitation during the CAPE (and possibly lower temperatures during CAPE I) drove many plant species 500 to 1000 m downslope, enriching local xerophytic communities especially with species from the Poaceae, Asteraceae and Solanaceae families[31,32] Such climate-driven increases in local diversity may have resulted in increases in the abundance of plant pathogens over time, a further hypothesis we explore here
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