EUROPEAN JOURNAL OF ENTOMOLOGY

Eur. J. Entomol. 119: 368-378, 2022 | DOI: 10.14411/eje.2022.038

Specialised chemistry affects insect abundance but not overall community similarity in three rare shrub willows: Salix myrtilloides, S. repens and S. rosmarinifoliaOriginal article

Petr KOZEL ORCID...^{1, 2}, Jing Vir LEONG ORCID...^{1, 2}, Igor MALENOVSKÝ ORCID...³, Jan ŠUMPICH ORCID...⁴, Jan MACEK ORCID...⁴, Jan MICHÁLEK ORCID...¹, Nela NOVÁKOVÁ ORCID...², Brian E. SEDIO ORCID...^{5, 6}, Carlo L. SEIFERT ORCID...⁷, Martin VOLF ORCID...^{1, 2}

¹ Institute of Entomology, Biology Centre of the Czech Academy of Sciences, Branisovska 31, CZ-37005 Ceske Budejovice, Czech Republic; e-mails: petrkozel.kozel@seznam.cz, jing.leong@entu.cas.cz, jan.michalek@entu.cas.cz, volf@entu.cas.cz

² Faculty of Science, University of South Bohemia, Branisovska 31, CZ-37005 Ceske Budejovice, Czech Republic, e-mail: nelak.gero@seznam.cz

³ Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlarska 2, CZ-61137 Brno, Czech Republic; e-mail: malenovsky@sci.muni.cz

⁴ Department of Entomology, National Museum, Natural History Museum, Cirkusova 1740, CZ-19300 Praha 9, Czech Republic; e-mails: jansumpich@seznam.cz, janmacek@nm.cz

⁵ Department of Integrative Biology, University of Texas at Austin, 2415 Speedway, Austin, TX 78712, USA; e-mail: sediob@utexas.edu

⁶ Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama

⁷ Department of Forest Nature Conservation, Faculty of Forest Sciences and Forest Ecology, Georg-August-University Göttingen, Büsgenweg 3, DE-37077 Germany; e-mail: carlo_seifert@web.de

Willows serve as a keystone host-plant genus for insect herbivores. The diversity of insect herbivore assemblages harboured by willows is typically affected by the diversity of specialised metabolites that willows produce. Here, we studied three small, shrubby willow species (Salix myrtilloides, S. repens and S. rosmarinifolia) that primarily occur at sites of high conservation value in the Czech Republic. We explored if associated insect communities reflect the specialised chemistry in these uncommon host plants. We measured the three willow species for overall metabolomic profiles and salicinoids using non-targeted metabolomics and sampled them for caterpillars, leaf-chewing beetles (adults and larvae), sawfly larvae, and sap-sucking Hemiptera. We detected 2,067 metabolites across the three willow species. Most of them were shared by S. repens and S. rosmarinifolia, while S. myrtilloides showed a distinct chemical profile. Salix repens and S. rosmarinifolia also had significantly higher concentration and richness of salicinoids than S. myrtilloides. The abundance of all insect species and generalists that also feed on host-plants outside Salicaceae was higher on S. myrtilloides than on S. rosmarinifolia or S. repens. The abundance of Salicaceae specialists did not differ among the three willow species. Insect community composition, in contrast, did not show pronounced differences among the three willows. Our results suggest that salicinoids may be responsible for the low abundance of generalist herbivores. Furthermore, our study indicates that herbivore community composition does not reflect the specialised chemistry in the three willows we studied. Therefore, we hypothesise that the presence of some of the insect species is primarily determined by other factors, such as the habitat type where the respective willow species occur. Although the studied willows possess some characteristic specialised chemistry, we conclude that their importance as hosts of specific and sometimes threatened insect fauna may be mediated by willow habitat preference.

Keywords: Insects, herbivore, host plants, concentration and richness of metabolites, salicinoids, Salicaceae, Salix, secondary metabolites, Czech Republic

Received: April 4, 2022; Revised: August 18, 2022; Accepted: August 18, 2022; Published online: September 1, 2022  Show citation