Disentangling the effects of latitudinal and elevational gradients on bee, wasp, and ant diversity in an ancient Neotropical mountain range

Aim: Ancient tropical mountains are megadiverse, yet little is known about
the distribution of their species. We aimed to disentangle the effects of
latitudinal and elevational gradients on the distribution of species of
Aculeata and to understand the effects of climatic variables across
different spatial scales of diversity (α, γ, and β-diversity). Location:
Campo rupestre in the Espinhaço Mountain Range, Southeast Brazil. Taxon:
Bees, wasps, and ants (Aculeata: Hymenoptera) Methods: We used a unique
dataset built from sampling species of Aculeata at 24 study sites across
12 mountains, covering 1200 km from south to north and an elevational
range of 1000 to 2000 m. We explored the elevational and latitudinal
patterns of α (site), γ (mountain), and β-diversity among samples at each
location (β Local). We also tested the effect of elevational range on
β-diversity in each mountain (β Mountain) and, on a larger scale (β
Regional), if β-diversity is influenced by geographical and environmental
distances. Finally, we tested whether climatic variables underpin the
observed patterns. Results: Latitude had no effect on diversity. We found
a decrease in both site and mountain diversity and, only for bees, β Local
increased with elevation. Climatic variables (temperature, wind, and
precipitation) and their interactions were important drivers of diversity,
with temperature being the most important. Finally, β Mountain increased
with mountain elevation range, and β Regional increased with the
geographical and environmental distances. Main conclusions: Our results
showed that variation in species richness and composition across mountains
is strongly associated with elevational gradient, which showed stronger
climatic variation than latitudinal gradient. Therefore, despite having
narrow elevational ranges, the biogeographical effects of tropical
mountains drive high diversity. Facing global climate changes, this
limited elevational gradient may limit species range shifts, leading to
severe biodiversity losses.

目的：古老的热带山脉具有极高的生物多样性，但人们对其物种分布知之甚少。本研究旨在厘清纬度与海拔梯度对针尾部（Aculeata）物种分布的影响，并解析气候变量在不同空间多样性尺度（α多样性、γ多样性及β多样性，α/γ/β-diversity）上的作用。

地点：巴西东南部埃斯皮尼亚苏山脉（Espinhaço Mountain Range）的岩石草地（Campo rupestre）。

类群：蜜蜂、黄蜂与蚂蚁（针尾部：膜翅目，Aculeata: Hymenoptera）

方法：本研究采用独特的数据集，该数据集通过对12座山体中24个研究位点的针尾部物种采样构建而成，覆盖南北跨度1200公里、海拔范围1000至2000米的区域。我们探究了α（位点）、γ（山体）及局域β多样性（β Local）在海拔与纬度梯度上的分布模式；同时检验了海拔范围对山体β多样性（β Mountain）的影响，并在更大尺度（区域β多样性，β Regional）上分析β多样性是否受地理距离与环境距离的影响。最后，我们验证了气候变量是否为观测模式的核心驱动因素。

结果：纬度对多样性无显著影响。我们发现位点与山体尺度的多样性均呈下降趋势，且仅蜜蜂的局域β多样性随海拔升高而增加。气候变量（温度、风与降水）及其交互作用是多样性的重要驱动因子，其中温度的作用最为关键。此外，山体β多样性随山体海拔范围扩大而增加，区域β多样性则随地理距离与环境距离增大而上升。

主要结论：研究结果表明，跨山体的物种丰富度与组成变化与海拔梯度密切相关，且海拔梯度的气候变异程度显著高于纬度梯度。因此，尽管热带山脉的海拔范围较窄，其生物地理效应仍能维持较高的多样性水平。面对全球气候变化，这种有限的海拔梯度可能限制物种分布区的迁移，进而导致严重的生物多样性丧失。