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bioRxiv · 10.64898/2026.07.17.738652

Beyond deadwood volume: structural heterogeneity and species-specific dispersal shape saproxylic beetle genetics

Krovi, R. S.·Amer, N. R.·Wierzbicka, A.·Plewa, R.·Kadej, M.·Jaworski, T.·Smolis, A.·Szmatola, T.·Oczkowicz, M.·Kajtoch, L.
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Abstract

Many rare saproxylic (deadwood-dwelling) beetles are among Europes most threatened insects, yet the relative importance of local microhabitat quality versus broad-scale landscape connectivity in shaping their genetic integrity remains poorly understood. We evaluated environmental drivers for 13 saproxylic beetle species--rare old-growth specialists, common taxa, and economically significant pests--across eight major forest complexes in Poland, using double digest restriction-site associated DNA sequencing (ddRAD-seq) paired with plot-level structural inventories and estimated effective migration surfaces (EEMS) modelling. A beta generalized linear mixed model identified deadwood diversity as the only significant within-species predictor of observed heterozygosity ({beta} = 0.041, 95% CI 0.0227-0.0586, p < 10-); total deadwood volume, forest age, time since logging, stump density, and veteran tree density were not significant. Management-category contrasts in observed heterozygosity (Ho) and the inbreeding coefficient (Fis) were non-significant after Tukey adjustment. Predictor x ecological-tier interactions did not differ detectably between rare and common species for five of six structural predictors; time since last logging was the exception ({chi}{superscript 2} = 4.56, p = 0.033). EEMS patterns differed among species and fell into three broad groups: regional lineage barriers, asymmetrical corridors, and surfaces close to isolation- by-distance expectations. These results associate plot-level heterozygosity with deadwood diversity and show that regional gene-flow patterns cannot be generalised across saproxylic beetles. Conservation planning should therefore combine local deadwood restoration with species-specific assessment of landscape connectivity.

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Krovi, R. S., Amer, N. R., Wierzbicka, A., Plewa, R., Kadej, M., Jaworski, T., Smolis, A., Szmatola, T., Oczkowicz, M., Kajtoch, L.. 2026-07-22. Beyond deadwood volume: structural heterogeneity and species-specific dispersal shape saproxylic beetle genetics. https://doi.org/10.64898/2026.07.17.738652

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