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 indicating that human-mediated transport may serve as a pathway of 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.

Sorting out the plants responsible for a contamination with pyrrolizidine alkaloids in spice seeds by means of LC-MS/MS and DNA barcoding: Proof of principle with cumin and anise spice seeds.

High value commodities such as spices suffer from occasional contaminations of both chemical and biological origin. Consequently, quality control and safety monitoring has become a pressing issue for the spice industry. Two recent independent studies showed that at least one third of the analyzed cumin and green anise spice seeds samples surpassed the by the European Union recently established threshold value for toxic pyrrolizidine alkaloids (PAs) and their corresponding N-oxides (PANOs). These heterocyclic secondary plant metabolites are produced by a large number of different plant families. In those spice seeds, it was found by means of DNA metabarcoding, that predominant contamination was due to the presence of herbal material from the Heliotropium genus (Boraginaceae). Unfortunately, the use of this specific type of DNA-based identification remains controversial for the majority of the official instances and preference is still given to the use of more tangible classical approaches, including microscopy and chemical analysis. However, these methodologies often suffer from inherent drawbacks. Here we demonstrate that at least for spice seeds, a combinatory approach of microscopy, chemical analysis and classical DNA barcoding of the isolated contaminants using the matK and trnH-psbA loci, provides qualitative and quantitative information on the amount of plant material responsible for the contaminations and the extent of the contamination. The generated data also demonstrates that the presence of a very limited number of Heliotropium sp. seeds in a standard commercially available canister is sufficient to surpass the allowed threshold value, illustrating once more the importance of weed control.

Worldwide diversity of endophytic fungi and insects associated with dormant tree twigs.

International trade in plants and climate change are two of the main factors causing damaging tree pests (i.e. fungi and insects) to spread into new areas. To mitigate these risks, a large-scale assessment of tree-associated fungi and insects is needed. We present records of endophytic fungi and insects in twigs of 17 angiosperm and gymnosperm genera, from 51 locations in 32 countries worldwide. Endophytic fungi were characterized by high-throughput sequencing of 352 samples from 145 tree species in 28 countries. Insects were reared from 227 samples of 109 tree species in 18 countries and sorted into taxonomic orders and feeding guilds. Herbivorous insects were grouped into morphospecies and were identified using molecular and morphological approaches. This dataset reveals the diversity of tree-associated taxa, as it contains 12,721 fungal Amplicon Sequence Variants and 208 herbivorous insect morphospecies, sampled across broad geographic and climatic gradients and for many tree species. This dataset will facilitate applied and fundamental studies on the distribution of fungal endophytes and insects in trees.