Diez, J. J. | Search bioRxiv

bioRxiv2023

Diversity of RNA viruses in declining Mediterranean forests

Global change alters forestry habitats and facilitates the entry of new pathogens that dont share a co-evolution history with the forest, leading them into a spiral of decline. As a result, relationships between forests organisms get disbalanced. Under this scenario, RNA viruses are of particular interest, as they participate in many of such relationships thanks to their ability to infect a wide range of hosts, even from different kingdoms of life. For this reason, the study of RNA viruses is essential to understand how viral flow across different hosts might occur, and to prevent possible outbreaks of diseases in the future. In this work the RNA virus diversity found in trees, arthropods and fungi from declining Mediterranean forests is described. To this extent, three habitats (Quercus ilex, Castanea sativa and Pinus radiata) were sampled and RNAseq was performed on tree tissues, arthropods and fungi. 146 viral sequences were detected by searching for matches to conserved motifs of the RNA-dependent RNA polymerase (RdRP) using Palmscan. Up to 15 viral families were identified, with Botourmiaviridae (28.7%) and Partitiviridae (9.6%) being the most abundant. In terms of genome type, ssRNA(+) viruses were the most represented (83.5%), followed by dsRNA (15%) and two ssRNA(-) representatives. Viruses belonging to families with cross-kingdom capabilities such as Hypoviridae (1), Mitoviridae (6) and Narnaviridae (5) were also found. Distribution of viruses across ecosystems was: Q.ilex (57.5%), P.radiata (26.7%) and C.sativa (15.8%). Interestingly, two RdRP sequences had no matches in available viral databases. This work constitutes a starting point to gain insight into virus evolution and diversity occurring in forests affected by decline, as well as searching for novel viruses that might be participating in unknown infectious pathways.

microbiology↗

bioRxiv2023

Climate, host and geography shape insect and fungal communities of trees

Non-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance suggesting that human-mediated transport may facilitate the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

ecology↗