Multi-scale impacts of land use change and fragmentation on reptile diversity patterns in subtropical landscapes from Mexico

Land use change drives biodiversity loss, but fragmented landscapes can still support substantial biodiversity. To explore the dynamics between landscape characteristics and diversity, multi-scale analyses are needed. We examined the effect of land use change and fragmentation on reptile abundance and taxonomic and functional diversity patterns in two subtropical landscapes within the Sierra Madre del Sur, a biodiverse region in southern Mexico with urgent conservation needs. For this, we sampled reptile communities within different land use types (large and small forest patches, croplands and non-natural pastures), identifying environmental and landscape factors explaining such patterns at the local (i.e., within each land use type) and landscape (i.e., at surrounding areas of each land use type) scales. We also evaluated variations in species functional traits between land use types and identified functionally unique, specialized, and endangered species in conserved versus disturbed habitats. We observed greater trait diversity in forest patches, as well as functionally specialized, unique, and endangered species. Reptile abundance and diversity were positively related to local vegetation and forest cover within 100–500 m spatial extents from focal sites. At larger spatial extents, the presence of other land use types was an important driver of overall diversity. These findings underscore the conservation value of both large and small forest patches for reptile conservation, serving as source habitats for disturbed land uses. However, at broader scales, a more heterogeneous landscape may enhance overall diversity, so efforts should consider the conservation value of other land use types within the landscapes. A holistic conservation approach, integrating landscape-scale factors and local variables, is essential for understanding and preserving reptile diversity in these fragmented landscapes.

This dataset can be used to reproduce the analyses performed in this research. Particularly, we provide data to:

1) Calculate reptile taxonomic and functional diversity, functional diversity standardized effect sizes, using Hill’s numbers, and functional uniqueness, functional specialization and the FUSE (functionally unique, specialized, and endangered) indexes, in the four land use types evaluated.
2) Perform a RLQ and Fourth-corner analysis to evaluate variations in species functional traits between land use types.
3) Model the relationships between both diversity dimensions, and local and landscape-scale variables using generalized additive models (GAMs), and identify the scale of effect (i.e., the scale where environmental variables have the most influence on diversity) for each dependent variable.

土地利用变化会驱动生物多样性丧失，但破碎化景观仍可维系可观的生物多样性。为探究景观特征与生物多样性之间的动态关联，需开展多尺度分析。本研究聚焦墨西哥南部生物多样性丰富且亟需开展保护工作的南马德雷山脉（Sierra Madre del Sur）区域内的两处亚热带景观，考察了土地利用变化与破碎化对爬行动物丰度、分类多样性及功能多样性格局的影响。
为此，我们在不同土地利用类型（大小型森林斑块、农田与非天然牧场）内对爬行动物群落进行了系统采样，识别出可解释局域尺度（即各土地利用类型内部）与景观尺度（即各土地利用类型周边区域）多样性格局的环境与景观因子。此外，我们还评估了不同土地利用类型间物种功能性状的差异，并识别出保护栖息地与受干扰栖息地中具备功能独特性、特化性及濒危属性的物种。
研究结果显示，森林斑块内的功能性状多样性更高，同时存在功能特化、独特且濒危的物种。爬行动物丰度与多样性与局域植被覆盖度以及距样点100–500米空间范围内的森林占比呈正相关。在更大空间尺度上，其他土地利用类型的存在是驱动整体多样性的关键因素。
上述研究结果凸显了大小型森林斑块对爬行动物保护的核心价值，其可作为受干扰土地利用类型的源生境。然而在更宽泛的空间尺度下，更为异质的景观或许可提升整体生物多样性，因此保护工作应兼顾景观内其他土地利用类型的保护价值。整合景观尺度因子与局域变量的整体性保护方案，对于理解并保护这些破碎化景观中的爬行动物多样性至关重要。

本数据集可用于复现本研究中开展的各项分析。具体而言，我们提供的数据可用于：
1) 在所评估的四类土地利用类型中，计算爬行动物的分类与功能多样性、基于希尔数（Hill’s numbers）得到的功能多样性标准化效应量，以及功能独特性、功能特化性与FUSE（功能独特、特化且濒危）指数；
2) 开展RLQ分析与四角落（Fourth-corner）分析，以评估不同土地利用类型间物种功能性状的差异；
3) 利用广义可加模型（GAMs）构建多样性维度、局域与景观尺度变量间的关联模型，并识别各因变量的效应尺度（即环境变量对多样性影响最强的空间尺度）。