Data from: Forest age is a primary trait filter for saproxylic beetles in the southeastern United States

Data from: Forest age is a primary trait filter for saproxylic beetles in the southeastern United States Clayton R. Traylor, Michael D. Ulyshen, Joseph V. McHugh, Ryan C. Burner Forest Ecology and Management 553: 121545. https://doi.org/10.1016/j.foreco.2023.121545 Corresponding author: Clayton R. Traylor, [e-mail] Abstract Many forests throughout the world consist of regenerating mature stands. Although these forests differ in many respects from old-growth (with a history of minimal human disturbance), they typically develop similar structural attributes over time. As a result, older mature forests may be of particular conservation value if they contain resources and microhabitats benefitting saproxylic (deadwood dependent) species. Species' response to forest age may be driven by traits that relate to ecological functions or habitat preferences, such that species with less compatible traits for a local forest environment are "filtered" out. Thus, forest age may influence species' distributions and the trait composition of assembled communities. The Piedmont region of the southeastern United States has experienced widespread forest regrowth over the past century due to agricultural abandonment. Today's landscapes are largely characterized by mature forests that are becoming increasingly fragmented by suburbanization. Here, we assessed the filtering effects of forest age, landscape forest cover (LFC), and deadwood volume on saproxylic beetles in northeastern Georgia. Using historic aerial imagery to distinguish forest age (young = regrown after 1938; old = mature in 1938), we sampled beetles in mature forests of both age classes occurring along an LFC gradient. We measured five traits with hypothesized functional roles (body length, body width, body roundness, antenna length, eye length) for the 472 species captured. Using a joint species distribution model (JSDM), we tested trait-niche relationships (i.e., how traits influence species' responses) and estimated community trait composition (mean and dispersion of trait values) along gradients of environmental filters. We found that forest age is a filter for several traits (six supported relationships with >95% posterior probability), but LFC and deadwood volume were less strongly related to fewer traits. Most notably, large species (typically having lower population sizes and requiring stable larval habitat) were filtered from young mature forests and low LFC. Thus, old mature forests with high LFC showed higher mean and dispersion of beetle body length. Sensory traits also showed responses, likely reflecting adult life under bark (eye length) or ability to detect resources or mates (antenna length). Body width and roundness showed inconsistent responses with regard to indicated functional roles. Our results show that forest age is a strong filter on saproxylic beetle communities in the southeastern United States. Old mature forests, despite their scarcity in the region, are important for species requiring habitat stability and for maintaining communities with diverse trait composition.数据来源：《林龄是美国东南部朽木栖性（saproxylic）甲虫的核心性状筛选因子》 作者：克莱顿·R·特雷勒（Clayton R. Traylor）、迈克尔·D·尤利申（Michael D. Ulyshen）、约瑟夫·V·麦克休（Joseph V. McHugh）、瑞安·C·伯纳（Ryan C. Burner） 期刊：《森林生态学与管理（Forest Ecology and Management）》，第553卷，文章编号：121545 DOI：https://doi.org/10.1016/j.foreco.2023.121545 通讯作者：克莱顿·R·特雷勒，邮箱：[e-mail] 摘要 全球多数森林均由经天然更新的成熟林分构成。尽管此类森林与原始林（人类活动干扰极少的原生林）在诸多维度存在差异，但随时间推移通常会形成相似的结构特征。因此，若老龄成熟林含有惠及朽木栖性物种的资源与微生境，其将具备特殊的保护价值。物种对林龄的响应由与生态功能或生境偏好相关的性状驱动，与当地森林环境适配性较弱的物种会被"筛选"淘汰。由此，林龄可影响物种分布以及群落组装后的性状组成。 美国东南部的皮埃蒙特（Piedmont）地区在过去一个世纪因农业撂荒经历了大范围的森林恢复。如今该区域景观以成熟林为主，但郊区化进程正使森林日益碎片化。本研究针对佐治亚州东北部的朽木栖性甲虫，评估了林龄、景观森林覆盖率（landscape forest cover, LFC）以及枯木蓄积量的筛选效应。研究借助历史航空影像区分林龄：幼龄林指1938年后恢复的森林，老龄林指1938年已成熟的森林；随后在沿LFC梯度分布的两类林龄的成熟林中开展甲虫采样。针对捕获的472个物种，我们测定了5个假定具备功能作用的性状：体长、体宽、体圆度、触角长度以及眼长。本研究采用联合物种分布模型（joint species distribution model, JSDM），检验了性状-生态位关系（即性状如何影响物种响应），并沿环境筛选梯度估算了群落性状组成（性状值的均值与离散度）。 研究结果显示，林龄对多个性状存在筛选效应（6个关联得到了>95%后验概率的支持），而LFC与枯木蓄积量与较少性状的关联度较弱。最显著的是，体型较大的物种（通常种群规模较小且需要稳定的幼虫生境）在幼龄成熟林与低LFC环境中被筛选淘汰。因此，具备高LFC的老龄成熟林，其甲虫体长的均值与离散度均更高。感官性状同样呈现响应，这可能反映了成虫在树皮下的生活（眼长）或探测资源与配偶的能力（触角长度）。体宽与体圆度的响应与假定的功能角色并不一致。本研究表明，林龄是美国东南部朽木栖性甲虫群落的强筛选因子。尽管该区域老龄成熟林十分稀缺，但它们对于依赖生境稳定性的物种以及维持性状组成多样的群落而言至关重要。