Ground beetle (Carabidae) abundance data from north-eastern Australian rainforest, between June 2008 - January 2010, using pitfall traps

Understanding how the environment influences patterns of diversity is vital for effective conservation management, especially in a changing global climate. While assemblage structure and species richness patterns are often correlated with current environmental factors, historical influences may also be considerable, especially for taxa with poor dispersal abilities. Mountain-top regions throughout tropical rainforests can act as important refugia for taxa characterised by low dispersal capacities such as flightless ground beetles (Carabidae), an ecologically significant predatory group. We surveyed flightless ground beetles along elevational gradients in five different subregions within the Australian Wet Tropics World Heritage Area to investigate (1) whether the diversity and composition of flightless ground beetles are elevationally stratified, and, if so, (2) what environmental factors (other than elevation per se) are associated with these patterns. Generalised linear models and model averaging techniques were used to relate patterns of diversity to environmental factors. Unlike most taxonomic groups, flightless ground beetles increased in species richness and abundance with elevation. Additionally, each subregion consisted of distinct assemblages containing a high level of regional endemic species. Species richness was most strongly positively associated with the historical climatic conditions and negatively associated with severity of recent disturbance (treefalls) and current climatic conditions. Assemblage composition was associated with latitude and current and historical climatic conditions. Our results suggest that distributional patterns of flightless ground beetles are not only likely to be associated with factors that change with elevation (current climatic conditions), but also factors that are independent of elevation (recent disturbance and historical climatic conditions). Variation in historical vegetation stability explained both species richness and assemblage composition patterns, probably reflecting the significance of upland refugia at a geographic time scale. These findings are important for conservation management as upland habitats are under threat from climate change.

探究环境如何塑造多样性格局，对于高效的保护管理工作至关重要，在全球气候持续变化的当下尤为如此。尽管群落结构与物种丰富度格局常与当前环境因素相关联，但历史遗留影响同样不容忽视，尤其是对于扩散能力较弱的类群而言。遍布热带雨林的山地山顶区域，可作为扩散能力较低的类群的重要避难所，比如无翅地面甲虫（flightless ground beetles），隶属于步甲科（Carabidae）——这是一类生态意义重大的捕食性类群。我们在澳大利亚湿热带世界遗产地内的五个不同亚区域，沿海拔梯度开展无翅地面甲虫调查，旨在探究两个核心问题：其一，无翅地面甲虫的多样性与群落组成是否随海拔呈现分层格局；其二，若存在此类格局，除海拔本身外，还有哪些环境因素与之相关。本研究采用广义线性模型与模型平均技术，将多样性格局与环境因素进行关联分析。与多数类群不同，无翅地面甲虫的物种丰富度与个体丰度均随海拔升高而增加。此外，每个亚区域均拥有独特的甲虫群落，且包含大量区域特有物种。物种丰富度与历史气候条件呈最强正相关，而与近期干扰（树木倒伏）的严重程度及当前气候条件呈负相关。群落组成则与纬度、当前及历史气候条件均存在关联。本研究结果表明，无翅地面甲虫的分布格局不仅可能与随海拔变化的因素（如当前气候条件）相关，还与不受海拔影响的因素（如近期干扰与历史气候条件）有关。历史植被稳定性的差异可解释物种丰富度与群落组成格局，这大概率反映了山地避难所在地理时间尺度上的重要意义。鉴于山地生境正面临气候变化带来的威胁，本研究结果对于保护管理工作具有重要参考价值。