Climate and vegetation structure shape ant communities along elevational gradients on the Colorado Plateau

Aim: Terrestrial animal communities are largely shaped by vegetation and climate. With climate also shaping vegetation, can we attribute animal patterns solely to climate? To understand this, we compare the relative and interactive effects of climate and vegetation on an animal community. Our study observes ant community changes along climatic gradients (i.e. elevational gradients) within different habitat types (i.e. open and forest). We compare the explanatory powers and effect sizes of climate and vegetation variables on ant communities and describe what drives elevational distributions of ant species.

Location: Colorado Plateau, southwestern United States

Taxon: Formicidae

Methods: We sampled ants and vegetation along two elevational gradients spanning 1132m with average annual temperature and precipitation differences of 5.7C° and 645 mm, respectively. Regression analysis and structural equation modeling was then used to test the relative effects of climate and vegetation variables on ant communities.

Results: Climate variables had the strongest correlations and the largest effect sizes on ant communities, while vegetation composition, richness, and primary productivity were relatively small. Precipitation was the strongest predictor for most ant community metrics. Ant richness and abundance had a negative relationship with precipitation in forested habitats, and positive in open habitats.

Main conclusions: Our results show strong direct climate effects on ants with little or no effects of vegetation composition or primary productivity, but contrasting patterns between vegetation type (i.e. forested vs open) with precipitation. This indicates vegetation structure can modulate climate responses of ant communities. Our study demonstrates climate-animal relationships may vary among vegetation types which can impact both findings from elevational studies and how communities will react to changes in climate.

Methods
Ants through pit fall traps, vegetation through point intercept in 1m2 plots

研究目的：陆地动物群落主要受植被与气候共同塑造。鉴于气候本身亦可塑造植被格局，那么能否将动物群落的分布模式完全归因于气候因素？为解答这一科学问题，本研究对比了气候与植被对动物群落的相对作用及交互效应。本研究针对不同生境类型（即开阔生境与森林生境）下沿气候梯度（即海拔梯度）分布的蚂蚁群落变化展开观测，对比气候与植被变量对蚂蚁群落的解释能力与效应量，并阐明驱动蚂蚁物种海拔分布格局的核心调控因素。
研究地点：美国西南部科罗拉多高原（Colorado Plateau）
研究类群：蚁科（Formicidae）
研究方法：本研究沿两条海拔梯度开展蚂蚁与植被采样，总海拔跨度达1132米，对应年均温差异5.7℃、年降水量差异645毫米。蚂蚁采样采用陷坑诱捕法（pit fall traps），植被调查则在1m2样方中通过样点截距法（point intercept）完成。随后采用回归分析与结构方程模型（structural equation modeling），检验气候与植被变量对蚂蚁群落的相对影响。
研究结果：气候变量与蚂蚁群落的相关性最强，效应量也最大；而植被组成、物种丰富度及初级生产力的影响相对较弱。降水是多数蚂蚁群落指标的最强预测因子。在森林生境中，蚂蚁物种丰富度与个体数量与降水呈负相关关系，而在开阔生境中则呈正相关关系。
主要结论：本研究结果显示，气候对蚂蚁群落具有显著的直接调控作用，植被组成或初级生产力的影响则微弱甚至可忽略；但植被类型（森林生境与开阔生境）与降水的交互效应呈现出相反的格局。这表明植被结构可调节蚂蚁群落对气候的响应模式。本研究证实，气候与动物群落的关系会因植被类型而异，这一结论既会影响海拔梯度研究的相关发现，也可为预测群落对气候变化的响应提供科学参考。