Data from: Divergent habitat use of two urban lizard species

Faunal responses to anthropogenic habitat modification represent an important aspect of global change. In Puerto Rico, two species of arboreal lizard, Anolis cristatellus and A. stratulus, are commonly encountered in urban areas, yet seem to use the urban habitat in different ways. In this study, we quantified differences in habitat use between these two species in an urban setting. For each species, we measured habitat use and preference, and the niche space of each taxon, with respect to manmade features of the urban environment. To measure niche space of these species in an urban environment, we collected data from a total of six urban sites across four different municipalities on the island of Puerto Rico. We quantified relative abundance of both species, their habitat use, and the available habitat in the environment to measure both microhabitat preference in an urban setting, as well as niche partitioning between the two different lizards. Overall, we found that the two species utilize different portions of the urban habitat. Anolis stratulus tends to use more “natural” portions of the urban environment (i.e., trees and other cultivated vegetation), whereas A. cristatellus more frequently uses anthropogenic structures. We also found that aspects of habitat discrimination in urban areas mirror a pattern measured in prior studies for forested sites in which A. stratulus was found to perch higher than A. cristatellus and preferred lower temperatures and greater canopy cover. In our study, we found that the multivariate niche space occupied by A. stratulus did not differ from the available niche space in natural portions of the urban environment and in turn represented a subset of the niche space occupied by A. cristatellus. The unique niche space occupied by A. cristatellus corresponds to manmade aspects of the urban environment generally not utilized by A. stratulus. Our results demonstrate that some species are merely tolerant of urbanization while others utilize urban habitats in novel ways. This finding has implications for long-term persistence in urban habitats and suggests that loss of natural habitat elements may lead to nonrandom species extirpations as urbanization intensifies.动物群落对人为生境改造（anthropogenic habitat modification）的响应，是全球变化研究的重要组成部分。在波多黎各岛，两种树栖蜥蜴（arboreal lizard）——安乐蜥（Anolis cristatellus）与安乐蜥（A. stratulus）——在城市区域中较为常见，但二者对城市生境的利用模式存在显著差异。 本研究针对城市生境中这两个物种的生境利用差异展开定量分析。针对每个物种，我们围绕城市环境的人工构筑物特征，定量测定了其生境利用情况、生境偏好，以及各该类群的生态位空间（niche space）。 为测定这两个物种在城市环境中的生态位空间，我们在波多黎各岛的4个行政区内共计6处城市样地开展了数据采集工作。 我们定量统计了两个物种的相对丰度（relative abundance）、生境利用情况，以及环境中可利用生境的特征，以此分析城市生境下的微生境偏好（microhabitat preference），同时探究两种蜥蜴间的生态位分化（niche partitioning）模式。 整体而言，研究结果显示两个物种对城市生境的利用区段存在明显分异。A. stratulus更倾向于利用城市生境中更具"自然属性"的区域（如树木与其他栽培植被），而Anolis cristatellus则更频繁地使用人工构筑物。 此外，我们发现城市生境中的生境选择模式，与此前森林生境中的研究结果一致：A. stratulus的停栖高度高于Anolis cristatellus，且偏好更低的温度与更高的冠层覆盖度（canopy cover）。 本研究中，A. stratulus所占据的多变量生态位空间，与城市生境中自然区域的可利用生态位空间并无显著差异，且该生态位空间恰好是Anolis cristatellus所占据生态位空间的一个子集。 Anolis cristatellus所特有的生态位空间，则对应A. stratulus一般不会利用的城市人工环境区域。 本研究结果表明，部分物种仅能耐受城市化生境，而另有部分物种则以全新的方式利用城市生境。 该发现对于物种在城市生境中的长期存续具有重要启示，同时也提示：随着城市化进程加剧，自然生境要素的丧失可能会引发非随机的物种局部绝灭（extirpation）事件。