Forest decline differentially affects trophic guilds of canopy-dwelling beetles

Abstract

<jats:title>Abstract</jats:title><jats:sec><jats:title>Context</jats:title><jats:p>Decline in a context of climate change is expected to induce considerable changes in forest structure, potentially affecting habitat opportunities and trophic resources for numerous species. Nonetheless, the consequences of decline on forest biodiversity have rarely been studied.</jats:p></jats:sec><jats:sec><jats:title>Aim</jats:title><jats:p>We aimed to characterize the impact of oak decline on different guilds of canopy-dwelling beetles.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Beetles were sampled for three consecutive years in oak stands exhibiting different levels of decline. Several guilds were considered: (i) Buprestidae, (ii) other saproxylic beetles split into wood-boring species and non-wood-boring species, (iii) seed-eating weevils, and (iv) specialist and generalist leaf-eating weevils.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Overall, decline had positive effects on the abundance and biomass of beetles, though contrasting variations were observed at the species or guild levels. Xylophagous species, especially the main oak-associated buprestids, and other saproxylic species benefitted from decline conditions. However, at odds with the insect performance hypothesis, decline had a positive effect on generalist phyllophagous species, a negative effect on specialist phyllophagous species, and a null effect on seminiphagous species.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>The increase in species richness for saproxylic and phyllophagous beetle communities suggests that decline might promote forest biodiversity. Our results call for further studies to thoroughly assess the functional outcomes of forest decline, and to suggest management strategies for conservation biologists.</jats:p></jats:sec><jats:sec><jats:title>Key message</jats:title><jats:p>Decline can affect the structure, resources and microclimates of the forest canopy, and potentially have cascading effects on canopy-dwelling species. Our survey shows that an oak decline can promote saproxylic beetles, especially xylophagous ones, and generalist phyllophagous weevils. However, it negatively affects specialist phyllophagous species and has no effect on seminiphagous weevils.</jats:p></jats:sec>

On the importance of getting fine‐scale temperature records near any surface

“…In the future, the call could be expanded to other types of interfaces with the atmosphere including plant organ temperature (e.g., leaf surfaces and plant inner tissues such as stems, woody tissues or galls) and the temperature of different layers in water bodies (ponds, rivers, wetlands). Indeed, the forest canopy, along with soil, is one of the key forest 'compartments' supporting tremendous forest biodiversity (e.g., Parmain et al, 2020) and aquatic thermal environments are still missing for global analysis (van Klink et al, 2020).…”