Data from: Size-dependent behavioral and antennal responses to doses of (+)-isopinocamphone and 1,8-cineole mixed with pheromone: a potential host selection strategy in female Ips typographus L.

Context:Ips typographus, a major pest of Norway spruce (Picea abies) in
Europe, is experiencing more frequent outbreaks due to climate change.
These outbreaks involve shifts in population dynamics and phenotypic
traits, influencing beetle responses to olfactory cues from stressed host
trees. Aims:The study examines the size-dependent behavioral and antennal
responses of female I. typographus to two host selection–deciding
volatiles with contrasting ecological roles: 1,8-cineole, which inhibits
attraction to unsuitable trees, and (+)-isopinocamphone, a pheromone
synergist. Size-linked morphological and olfactory adaptations may
influence females' ability to select suitable host trees for
reproduction. Methods:In field trap experiments conducted in 2019 and
2022, the body size of I. typographus females caught in response to
different doses of (+)-isopinocamphone or 1,8-cineole in combination with
pheromone was compared. Female Ips typographus were sorted based on body
length, the size of the antennal club was measured, and size-dependent
antennal responses to these volatiles were analyzed using
electroantennography. Results:Larger females were more attracted to
(+)-isopinocamphone in combination with pheromone in the field, showed
stronger antennal detection, and had proportionally larger antennal clubs
than smaller females. In contrast, smaller females were less repelled by
1,8-cineole added to pheromone, but, in contradiction, antennally detected
it more strongly than larger females despite having smaller antennal
clubs. Conclusion: The total body length significantly influences
semiochemical detection in I. typographus females. (+)-isopinocamphone was
detected more effectively by larger females, implying an advantage in the
selection of suitable host trees. In contrast, the discrepancy between
behavioral and antennal responses to 1,8-cineole in smaller females
suggests involvement of not only peripheral detection but also central
nervous processing of olfactory signals driving behavior. This adaptation
may enable smaller females to reduce competition with large ones by
selecting less suitable trees. These findings provide new insights into
the ecological relationship between beetle morphology and olfactory cues,
with implications for tree–bark beetle interactions.