Correlates of extinction risk in squamate reptiles: the relative importance of biology, geography, threat and range size

Aim
Evaluating the relative roles of biological traits and environmental factors that predispose species to an elevated risk of extinction is of fundamental importance to macroecology. Identifying species that possess extinction-promoting traits allows targeted conservation action before precipitous declines occur. Such analyses have been carried out for several vertebrate groups, with the notable exception of reptiles. We identify traits correlating with high extinction risk in squamate reptiles, assess whether these differ with geography, taxonomy and threats, and make recommendations for future Red List assessments.

Location
Global.

Methods
We collected data on biological traits and environmental factors for a representative sample of 1139 species of squamate reptiles. We used phylogenetically controlled regression models to identify general correlates of extinction risk, threat-specific correlates of risk and realm-specific correlates of risk. We also assessed the relative importance of range size versus other factors through multiplicative bivariate models, partial regressions and variance partitioning.

Results
Range size was the most important predictor of extinction risk, reflecting the high frequency of reptiles assessed under range-based IUCN criteria. Habitat specialists occupying accessible ranges were at a greater risk of extinction: although these factors never contributed more than 10% to the variance in extinction risk, they showed significant interactions with range size. The predictive power of our global models ranged from 23% to 29%. The general overall pattern remained the same among geographical, taxonomic and threat-specific data subsets.

Main conclusions
Proactive conservation requires shortcuts to identify species at high risk of extinction. Regardless of location, squamate reptiles that are range-restricted habitat specialists living in areas highly accessible to humans are likely to become extinct first. Prioritizing species that exhibit such traits could forestall extinction. Integration of data sources on human pressures, such as accessibility of species ranges, may aid robust and time-efficient assessments of species extinction risk.

研究目标：阐明生物性状与环境因子在提升物种灭绝风险中的相对作用，是宏观生态学（macroecology）的核心议题之一。识别携带促灭绝性状的物种，可在种群出现急剧衰退前开展针对性保护行动。目前已有多个脊椎动物类群开展过此类分析，但爬行动物是显著的例外。本研究旨在明确与有鳞目爬行动物（squamate reptiles）高灭绝风险相关的性状，评估这些性状是否因地理分布、分类学类群及威胁类型而异，并为未来的红色名录（Red List）评估提供建议。
研究区域：全球范围。
研究方法：我们收集了1139种有鳞目爬行动物代表性样本的生物性状与环境因子数据。采用系统发育控制回归模型（phylogenetically controlled regression models），分别识别灭绝风险的通用关联因子、特定威胁类型下的风险关联因子以及特定生物地理域下的风险关联因子。同时通过乘性双变量模型、偏回归与方差分解方法，评估了分布范围大小相较于其他因子的相对重要性。
研究结果：分布范围大小是灭绝风险最关键的预测因子，这与依据基于分布范围的世界自然保护联盟（IUCN）评估标准开展爬行动物评估的高占比相符。栖息于易到达分布范围内的栖息地特化物种面临更高的灭绝风险：尽管这些因子对灭绝风险方差的解释度从未超过10%，但它们与分布范围大小存在显著的交互效应。本研究的全球模型预测能力介于23%至29%之间。在地理分区、分类学类群以及特定威胁类型的数据子集中，整体规律均保持一致。
主要结论：主动式保护需要快速识别高灭绝风险物种的方法。无论分布区域如何，分布范围受限且栖息于人类易到达区域的栖息地特化型有鳞目爬行动物，最有可能率先走向灭绝。优先保护具备此类性状的物种，可有效延缓其灭绝进程。整合人类活动压力相关数据（如物种分布范围的可及性），将有助于开展稳健且高效的物种灭绝风险评估。