Abstract Comparative studies of closely related species provide a powerful means of identifying the ecological and demographic factors associated with variation in mammalian social systems. Although most members of the subterranean rodent genus Ctenomys are thought to be solitary, the highland tuco-tuco (C. opimus) is group living, meaning that multiple adults share a burrow system and underground nest site. These animals are part of the opimus clade, a monophyletic collection of four named species that occur in northwestern Argentina and adjacent portions of Chile and Bolivia. As a first step toward generating a comparative assessment of social organization within this clade, we characterized spatial relationships among members of a population of Ctenomys at Antofagasta de la Sierra, Catamarca Province, Argentina. Based on geographic location and natural history, these animals were expected to be part of the opimus clade; analyses of mitochondrial cytochrome-b sequences from our study population confirmed this general phylogenetic placement. Radiotelemetry data indicated that the animals at Antofagasta were group living, with up to three adult females and one adult male sharing a burrow system. In contrast to other group-living ctenomyids, however, individuals did not consistently share nest sites. Comparisons of these data with re-analyses of spatial relationships among members of the population of C. opimus studied by O’Brien et al. (2020) revealed several intriguing differences in social organization, potential explanations for which include short-term responses to variable demographic and ecological conditions as well as more enduring responses to differences in local selective pressures. Further comparative analyses of these populations and, more generally, members of this subclade of Ctenomys will help to elucidate the factors contributing to variation in social behavior within this speciose and geographically widespread genus.

中文翻译：

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opimus进化枝中tuco-tucos（Ctenomys属）之间的可变社会组织

摘要 对密切相关物种的比较研究提供了一种强有力的手段来识别与哺乳动物社会系统变化相关的生态和人口因素。尽管大多数地下啮齿动物属 Ctenomys 被认为是独居的，但高地 tuco-tuco (C. opimus) 是群居的，这意味着多个成年人共享一个洞穴系统和地下巢穴。这些动物是 opimus clade 的一部分，opimus clade 是四个命名物种的单系集合，分布在阿根廷西北部以及智利和玻利维亚的邻近地区。作为对该进化枝内的社会组织进行比较评估的第一步，我们描述了阿根廷卡塔马卡省安托法加斯塔德拉谢拉的 Ctenomys 人口之间的空间关系。根据地理位置和自然历史，这些动物被认为是 opimus 进化枝的一部分。对来自我们研究人群的线粒体细胞色素-b 序列的分析证实了这种一般的系统发育位置。无线电遥测数据表明，安托法加斯塔的动物是群居的，最多三只成年雌性和一只成年雄性共用一个洞穴系统。然而，与其他群居的栉虫相比，个体并没有始终如一地共享巢穴。将这些数据与 O'Brien 等人研究的 C. opimus 种群成员之间空间关系的重新分析进行比较。（2020）揭示了社会组织中的几个有趣的差异，潜在的解释包括对可变的人口和生态条件的短期反应以及对当地选择压力差异的更持久的反应。对这些种群的进一步比较分析，更一般地说，这个 Ctenomys 亚群的成员将有助于阐明导致这个物种和地理分布广泛的属内社会行为变化的因素。