Host-selection behaviour and host-use patterns of saproxylic beetles in snags of aspen (Populus tremuloides Michaux) and black spruce (Picea mariana (Miller)) in the province of Québec, Canada
Bibliographic record
Abstract
The general objectives of this thesis project were to describe and to understand the dynamics creating occurrence patterns of saproxylic wood-feeding Coleoptera in snags (i.e., standing dead trees) of black spruce and aspen along the decay gradient. The first part of this thesis focuses on pre-landing host-selection behaviours in coniferophagous species, i.e. the use of host-produced volatiles to locate potential hosts. Results presented suggest that most saproxylic wood-feeding beetles studied herein use volatiles to orient towards potential habitat patches but that olfactive information does not allow the identification of suitable hosts at close range prior to landing. The second part of the thesis focuses on the occurrence patterns themselves and on underlying mechanisms. Sampling was conducted using snag dissection, a novel method allowing a better characterization of larval stage wood-feeding assemblages. Opposite patterns were observed between the two host species studied, as abundance and species richness were highest in early stages of decay in spruce, and in middle to late stages of decay in aspen. In aspen, numerous nutritional and physical parameters of dead wood correlated significantly with wood-borer occurrence. However, most of these parameters were strongly auto-correlated, and the explanatory model most highly ranked by model selection consisted of only a snag age term. Also, a simple neutral model based on temporal autocorrelation in occurrence probability produced patterns similar to those observed through sampling. In the last original paper presented, results suggest that wood-boring larvae select for specific types of substrate in highly variable aspen snags. This selection on the part of the larvae likely decreases the impact of the oviposition site on subsequent larval performance, and could explain the lack of strong selection seen on the part of the mother. My results suggest very different host-selection dynamics in black spruce and aspen, as assemblages of the former were dominated by early-decay species with volatiles-driven colonization dynamics, while middle- to late-decay species dominated the later, seemingly through mostly neutral colonization mechanisms. Some of my findings suggest that patterns observed in black spruce and aspen could be extrapolated to a coniferous/deciduous host dichotomy in colonization dynamics of woodfeeding species, based on divergent secondary chemistry and wood structure.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".