Hierarchical trait filtering at different spatial scales determines beetle assemblages in deadwood

Abstract

1. Environmental filters-including those resulting from biotic interactions-play a crucial role during the assembly of ecological communities. The importance of scale has thereby been acknowledged but filters at different scales have rarely been quantified in relation to each other, although these hierarchically nested filters eventually determine which communities assemble from a regional species pool.2. Saproxylic beetles offer an ideal system to study such hierarchically nested environmental filters. Three steps of filtering during the community assembly of these deadwood-dependent beetles are proposed. First, starting from a regional species pool, species must disperse to forest sites. Second, within a site, individuals need to find a patch with preferred microclimatic conditions. Third, the conditions of a single deadwood object (i.e. tree species identity, decomposition stage) at this patch will determine, which species colonise and establish.3. To study these hierarchical filters, we used unique long-term data ets of saproxylic beetle diversity from trap catches at 29 sites and from emergence traps on 694 experimentally installed deadwood logs at the same sites in three regions in Germany. To relate different environmental filters to beetle assemblages, we used a set of 13 functional traits that are hypothesised to relate to different filters at different scales.4. We show that all three hierarchical filtering steps resulted in reductions of functional diversity and simultaneous shifts in the functional composition of beetle assemblages, reflecting the roles of different traits in response to different

Saproxylic beetles' morphological traits and higher trophic guilds indicate boreal forest naturalness

“…Additionally, we found that the roundness of the saproxylic beetle's body was predictive of forest naturalness. Other research has found some indication that beetle body shape responds to forest structure (Barton et al, 2011;Micó et al, 2020;Hagge et al, 2021;Neff et al, 2022;Traylor et al, 2023), and this is enough to indicate that there may be an important mechanism at work. However, which mechanisms underlie this trait in relation to forest structure remain an open question.…”

“…Our findings also indicate that species with reduced dispersal ability are sensitive to intensive forest management. Research has also found that traits related to dispersal ability, including wing length, decreased with the proportion of broadleaf trees (Neff et al, 2022). Neff et al (2022) suggest that the mechanism behind this result is that conifers have been relatively recently introduced into Central Europe for forestry purposes, and conifer specialists with low dispersal abilities have not been able to establish themselves yet.…”

“…Research has also found that traits related to dispersal ability, including wing length, decreased with the proportion of broadleaf trees (Neff et al, 2022). Neff et al (2022) suggest that the mechanism behind this result is that conifers have been relatively recently introduced into Central Europe for forestry purposes, and conifer specialists with low dispersal abilities have not been able to establish themselves yet. However, this interpretation does not fit well with our results since we found similar effects in Northern Europe, where conifers have long been part of forests (Binney et al, 2017).…”

Drivers of community assembly change during succession in wood‐decomposing beetle communities

“…In addition to mechanisms acting at the deadwood‐log scale, community assembly of saproxylic communities is affected by spatial processes and environmental conditions (Neff et al, 2022). The composition of saproxylic communities varies spatially with beta‐diversity increasing with increasing spatial distance between deadwood logs both within (Bae et al, 2020; Müller et al, 2020) and among regions (Bae et al, 2020).…”

“…In addition to mechanisms acting at the deadwood-log scale, community assembly of saproxylic communities is affected by spatial processes and environmental conditions (Neff et al, 2022).…”