Data from: Among-species overlap in rodent body size distributions predicts species richness along a temperature gradient

The associated data files and R script are all that is required to reproduce the analyses in the manuscript "A thermal gradient of trait similarity across North America," published in Ecography: https://onlinelibrary.wiley.com/doi/10.1111/ecog.03641The following .csv files contain data required to reproduce the analysis, with raw unprocessed small mammal data from NEON, small mammal data that has been put through our QC code, mammal trait data compiled from different sources, and site-level environmental covariates: raw_NEON_mammal_data.csv, final_NEON_mammal_data.csv, mammal_traits.csv, site_covariates.csvThe following .csv files contain metadata describing the corresponding data file: final_NEON_mammal_data_meta.csv, mammal_traits_meta.csv, site_covariates_meta.csv. Each file lists the data sources. Please see documentation at neonscience.org for more information on the NEON small mammal trapping data.The following .R file is an R script, tested under R/3.3.3, that contains code to reproduce the analyses in the manuscript: code_supplement.RBelow is the abstract:Temperature is widely regarded as a major driver of species richness, but the mechanisms are debated. Niche theory suggests temperature may affect richness by filtering traits and species in colder habitats while promoting specialization in warmer ones. However, tests of this theory are rare because niche dimensions are challenging to quantify along broad thermal gradients. Here, we use individual-level trait data from a long-term monitoring network spanning a large geographic extent to test niche-based theory of community assembly in small mammals. We examined variation in body size among 23 communities of North American rodents sampled across the National Ecological Observatory Network (NEON), ranging from northern hardwood forests to subtropical deserts. We quantified body size similarity among species using a metric of overlap that accounts for individual variation, and fit a structural equation model to disentangle the relationships between temperature, productivity, body size overlap, and species richness. We document a latitudinal gradient of declining similarity in body size among species towards the tropics and overall increase in the dimensions of community-wide trait space in warmer habitats. Neither environmental temperature nor net primary productivity directly affect rodent species richness. Instead, temperature determines the community-wide niche space that species can occupy, which in turn alters richness. We suggest a latitudinal gradient of trait space expansion towards the tropics may be widespread and underlie gradients in species diversity.

本数据集配套的数据文件与R脚本即可复现发表于《Ecography》的论文《北美跨大陆性状相似性的温度梯度》（A thermal gradient of trait similarity across North America）中的分析流程，论文链接：https://onlinelibrary.wiley.com/doi/10.1111/ecog.03641。
以下CSV文件包含复现分析所需的全部数据，涵盖来自国家生态观测网络（NEON，National Ecological Observatory Network）的未处理小型哺乳动物原始数据、经本研究质控代码处理后的小型哺乳动物数据、多源整合的哺乳动物性状数据，以及样地尺度环境协变量数据：raw_NEON_mammal_data.csv、final_NEON_mammal_data.csv、mammal_traits.csv、site_covariates.csv。
以下CSV文件为对应数据文件的元数据：final_NEON_mammal_data_meta.csv、mammal_traits_meta.csv、site_covariates_meta.csv。各文件均列明了数据来源。如需了解NEON小型哺乳动物诱捕数据的更多细节，请查阅neonscience.org官网的文档。
以下R脚本文件（已在R/3.3.3环境下测试通过）包含复现论文分析的代码：code_supplement.R。
以下为论文摘要：
温度被广泛认为是物种丰富度的核心驱动因子之一，但其内在作用机制仍存在争议。生态位理论指出，温度可通过筛选寒冷生境中的性状与物种，并促进温暖生境中的特化作用来影响物种丰富度。然而，由于难以在宽泛的温度梯度上量化生态位维度，该理论的实证检验极为罕见。本研究借助覆盖广阔地理范围的长期监测网络获取的个体水平性状数据，检验小型哺乳动物群落构建的生态位理论。我们对国家生态观测网络（NEON）监测的23个北美啮齿动物群落的体型变异展开分析，这些群落涵盖从北部温带硬木林到亚热带荒漠的多种生境类型。本研究采用考虑个体变异的重叠度指标量化物种间的体型相似性，并构建结构方程模型以厘清温度、生产力、体型重叠度与物种丰富度之间的关联。研究结果显示，存在一条纬度梯度：向热带地区物种间的体型相似性逐渐降低，且温暖生境中群落整体性状空间的维度整体升高。环境温度与净初级生产力均未对啮齿动物物种丰富度产生直接影响。实际上，温度决定了物种可占据的群落级生态位空间，进而调控物种丰富度。我们提出，向热带地区扩张的性状空间纬度梯度可能广泛存在，并构成物种多样性纬度梯度的核心成因。