Identifying floral hosts of cerambycid beetles using palynology
Pollen is an important food source for many insects including the adults of beetles whose larvae are important forest pests. I quantified the distribution of pollen-feeding in adults of several species of long-horned beetles (Coleoptera: Cerambycidae). Palynivory by cerambycid beetles is common in the subfamily Lepturinae and occurs sporadically in Cerambycinae. The current knowledge of feeding in this group is inferred from floral host records, which are biased against tall trees because they are inaccessible to naturalists. I present a simplified palynological method for extracting and quantifying pollen from the frass of 21 species of beetles collected on flowers, with pheromone-baited panel traps, and at lights. I identified pollen grains to genus or species when possible and estimated abundances using calculations based on standardized markers added to samples. I found a higher abundance of pollen grains in the frass of palynivorous beetles collected on flowers than in the frass of beetles collected otherwise. I used the Shannon-Wiener Index to describe the diversity of pollen in the frass of beetles collected from flowers. There was high alpha diversity of pollen grains in the frass of Callimoxys sanguinicollis (Olivier) on Cornus drummondii C.A.Mey. (Cornaceae) and Molorchus bimaculatus Say on Cornus florida L. Next, I described the pollen taxa in the frass of palynivorous beetles collecting in traps and at lights by calculating the mean abundance and proportions of pollen taxa. I found Juglans nigra L. (Juglandaceae), Quercus L. (Fagaceae), and Vitis L. (Vitaceae) in frass from Anelaphus pumilus (Newman). Acer L. (Sapindaceae), Viburnum L. (Caprifoliaceae), and Quercus was found in frass from Cyrtophorus verrucosus (Olivier). I recorded Acer and Quercus pollen in the frass of Euderces pini (Olivier). Megacyllene caryae (Gahan) frass contained Quercus and Crataegus Tourn. (Rosaceae) pollen. Finally, the abundance, richness, and composition of pollen grains in the frass of Megacyllene caryae varied with collection date (e.g., April 17 vs. April 25, 2016) and location (e.g., forest vs. urban sites). These results provide insight into the natural history and feeding behavior of long-horned beetles, potentially influencing conservation or pest management strategies for forest insects. Moreover, I provide a method to secure evidence of palynivory in insects without having to carry out dissections or field observations.
Cerambycinae, Lepturinae, Cerambycidae, Quercus, Crataegus, Pollen, Palynology, Frass, Beetles, Herbivory, Palynivory, Flowers, Inflorescence, Anthesis, Phenology, Natural history
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign