Non-Random Distribution of Boreus hyemalis Among Bryophyte Hosts: Evidence from Field and Laboratory Tests

Our understanding of herbivorous insect's host selection is often based on observed associations with host plants, which can be biased by relative plant abundance, leading to inaccurate assumptions of preference. These biases may be particularly pronounced for insects associated with bryophytes, where dominance patterns are less evident. Estimating selection tendencies is also challenging for rare species with unique ecologies. Boreus hyemalis, a winter-active insect, associates with a range of bryophyte species, yet its specificity in moss-host selection remains unclear. This study investigates whether B. hyemalis shows non-random distribution among bryophyte species in natural habitats and laboratory settings. Field surveys revealed associations with 21 moss species, with significant selection tendencies toward Dicranella heteromalla and Hypnum cupressiforme, with moss species richness being a key factor for boreid inhabitance. Laboratory tests assessed selection among 14 moss species, including H. cupressiforme morphotypes, under controlled conditions. Results indicated Polytrichum formosum was the most frequently selected in the lab. Despite some discrepancies between field and lab findings, B. hyemalis shows specific selection tendencies for particular moss species. These results provide new insights into the ecological interactions between bryophytes and this winter-active insect, emphasizing the importance of moss structure and species richness in shaping B. hyemalis distribution.