Background & Summary

Biological invasions are known to dramatically affect biodiversity, ecosystem functioning, and human well-being1,2. Growing populations, socio-economic changes, along with the intensification of the global trade network are critical for the introduction and spread of alien species3,4. Overall, there are no general diagnostic traits that help to detect invasive taxa (“species invasiveness”), nor specific features to measure the susceptibility of ecosystems to invasion (“community-level invasibility”)5,6. Instead, the understanding of the potential threats caused by the introduction of non-native species invokes a complex combination of ecological, evolutionary (including biogeographic) and socio-economic factors7,8.

With about 6,500 described species worldwide, the subfamily Scolytinae is a hyperdiverse coleopteran group belonging to the weevil family Curculionidae. The biological activity of bark beetles depends upon a strict association with a remarkable variety of plants. Both adults and larvae feed and develop either in dead wood or different parts of live plants. For this reason, members of this group are commonly and accidentally moved outside their native ranges by means of global trades in several plant or wood products (e.g., logs, wood packaging materials, bonsai, ornamental plants)9,10. As a result, many species are nowadays considered to be economically important pests of native forest and agricultural crops globally11,12,13,14,15. For this reason, knowledge of host plants is a key element for policies to prevent the introduction of exotic organisms, as well as for the monitoring and interception protocols of exotic species16,17.

After the previous datasets on the Xyleborini tribe18,19, and two on miscellaneous tribes20,21,22,23, in this study we present a fourth host plant dataset of the remaining scolytine tribes: Hylastini LeConte, Hylurgini Gistel, Ipini Bedel, Phloeosinini Nusslin, and Polygraphini Chapuis, mainly associated with conifers. Within these tribes are some of the main pests for conifers (Araucariaceae Henkel & W.Hochst., Cupressaceae Gray, Pinaceae Spreng. ex F.Rudolphi, Podocarpaceae Endl., and Taxaceae Gray families), for example Dendroctonus genus (literally Dendro- tree, -tonus destroyer). The Hylurgini tribe includes some of the major conifer-killing scolytine. Most of them infest Pinus, but other genera can also be colonized24. Ips genus (Ipini tribe) infests mainly Pinus and Picea species and includes destructive species for conifer forests and plantations (e.g., I. confusus in southwestern USA and I. typographus in Europe)25,26,27. In the present catalogue, we treat the 829 bark beetle species belonging to these tribes. The dataset intends to be a comprehensive and easy-to-use reference tool for future bark beetle researches on ecology, evolution, biogeography and invasiveness surveys.

Methods

Host plant definition

In accordance with the principles proposed by Ruzzier et al.18, a specific and very broad definition of host plant was adopted in the compilation of this dataset, which does not just include ‘true host plants’. Only records of scolytine species observed boring inside any plant part or tissue (either at adult or larval stage) were accepted as a true insect-plant association. On the other hand, records derived from trapping or other observations of occurrence in forests or plantations (including monocultures) were considered unreliable and therefore not included in the dataset. In the dataset primary or secondary host plants were included, without distinctions, as well as usual or occasional hosts. These categorizations are not essential for preventing new introductions (that is the primary purpose of this dataset): in fact, even a secondary or occasional host can act as a pathway of introduction8. Moreover, several species can attack either the same host trees with different intensity, phylogenetically related species or completely different plants depending on whether they are in a native or invaded environment8,28,29,30. For these reasons, it was preferred to adopt a broader and more precautionary definition of “host”.

Data collection

In accordance with the previous works of the series, the initial scolytine checklist was based on the Wood & Bright catalog and following supplements24,31,32,33,34, and integrated with all papers published afterwards35,36,37. The current version of the dataset includes all the species described prior to 31 July 2024 and belonging to the following five tribes: Hylastini, Hylurgini, Ipini, Phloeosinini and Polygraphini.

The process was the same as that described in the previous works: each scolytine species was treated individually, using first the Wood & Bright catalog and following supplements, then searching the species name (e.g., “Scolytus amygdali”) in Google Scholar, Google and other sources referring to reliable scientific papers, books or databases. Synonyms of scolytine species and host taxa were also used in the search. In addition, we extensively reviewed documents in multiple languages (i.e., Chinese, English, French, German, Italian, Japanese, Portuguese, Russian, Spanish) using, when necessary, multilingual neural machine translators (DeepL or Google translate). When the host species in the original sources were reported only with vernacular or local names, or when uncertain and unreliable records were found, we discarded the information. In the case of multiple references dealing with the same species or reporting the same information, only one, and generally the first recovered or the most exhaustive, was selected and included in the dataset. All the cited and consulted sources are openly available.

Plant taxonomy follows the “Plant of The World Online” database38. The plant economic uses are reported from the “U.S. National Plant Germoplasm System” database39, which includes all the commercial uses of the whole plant, part of it, or from the materials and chemicals obtained by processing it. The three categories adopted are 1) “Food and pharmaceutical” (production of human and animal food, including bee plants; production of cosmetics, drugs, traditional medicine remedies, narcotics, vertebrate and invertebrate poison); 2) “Material” (production of fuel or raw materials used in other industries, such as wood, gum and resins); 3) “Environmental” (plants with ornamental value and plants used for reforestations or for environmental remediation, such as soil protection from erosion, shade and shelter).

Data Records

The dataset for the host plants species of these tribes is available on Zenodo with the original dataset in XLSX format (“Complete_dataset_conifers_Tribes.xlsx”)40. The dataset is organized in four sheets: “Versions” summarizes all the updates introduced with respect to the previous version of the dataset; “Dataset” is the complete dataset with the beetle-plant associations and economic uses of the hosts; “Economic Uses” provides the alphabetically ordered plant list with associated economic uses; “References” lists all the references (in alphabetical order) used in the creation of the dataset. “Dataset” sheet is organized in nine columns as follows: “Tribe” and “Species” include the taxonomic information on the scolytine beetles; “Host Family”, “Host Genus” and “Host Species” include information on the plants; “Reference” is where the beetle-plant association is reported (entries left blank refer to those scolytine species whose hosts remain unknown, both for lack of data and publications specifically indicating the missing information). The last three columns (“Food and pharmaceutical”, “Material” and “Environmental”) refer to the economic categories (“1” if the plant belongs to that category, “0” otherwise). Information was reported for plant species only. In the dataset, scolytine species are sorted alphabetically by tribe and species. Plant family and genus records (without plant species) do not imply that a specific scolytine species feeds on all the plants belonging to that category, but instead that family or genus is the most specific/detailed information available in the reviewed literature, thereby suggesting that a determined species feeds on at least one plant species belonging to that specific family/genus.

The data descriptor was peer reviewed in 2024 based on the data available on the platform at the time (Version 1.0). The dataset will be periodically updated with new versions (namely Version 1.0 onwards); the latest and most updated dataset will be the first to access via the DOI provided here, however previous versions of the same file will also remain available in the repository. The first version (1.0) provides information for 831 species of Scolytinae and a total of 3,129 potential insect-plant associations. 240 scolytine species have no host records available. Of the 591 species in which at least one host is known, 531 species have their host known at species level, while for 60 species our knowledge of the host is limited to the family or genus. The dataset includes records for 588 plant species, distributed among 63 families and 265 genera; conifers represent the majority of the hosts with 2476 insect-plant recorded associations. 370 plant species belong to at least one of the three economic categories considered.

Technical Validation

All host records included in the dataset are based on articles published in scientific journals, books, reports and databases managed by leading experts on scolytine beetles (e.g., Atkinson database: Bark and Ambrosia Beetles of the Americas)41. In addition, we included host records recovered from databases managed by international phytosanitary agencies (e.g., CABI42 and EPPO43), aware that in a few cases data provided may be considered uncertain as not counter-validated by scientific publications. Finally, even for data from peer-reviewed publications, there may be some questionable data. The presence of references for each individual record can help assess the reliability of any erroneous data that escaped the review process during the compilation of the dataset.

As already specified in materials and methods, to standardize and harmonize the information, we critically reviewed all the data collected, keeping only that related to the species whose relationship with the host plant could be recognized unequivocally; for this reason, we have excluded all possible cases that do not fall within the standards defined in the materials and methods section. Each record in the dataset is associated with a bibliographic reference, allowing users to assess the validity of the record, and reuse the data. We listed the references cited in the dataset, making it possible for users to access the original sources.

The complete list of genera and species belonging to the target tribes was compiled using Bright’s catalog34 and integrated/updated with the latest publications. Plant taxonomy follows the International Code of Nomenclature for algae, fungi and plants44. Taxon names and authors, including subspecies, varieties and hybrids are consistent with those provided in the internationally recognized POWO database and the International Plant Names Index (IPNI)45.

Since listing host plants is a dynamic activity, especially for non-native and invasive species, and taxonomy of Scolytinae is in continuous evolution, our aim is to keep updating the species list and host plant data starting from our direct research upon literature, as well as direct contribution from scolytine beetle researchers and stakeholders. Data will be corrected and updated if any errors or updates are reported to the first author (matteo.marchioro@unipd.it).