Social flexibility enables individuals to switch between group and solitary living and is suggested to be an adaptation to varying environments. Several previous studies on different species compared two populations and hypothesized that observed differences in the social organization were due to differences in population density but lacked the necessary sample size to test this prediction. In a previous 8-year long-term study, we showed that one population of African striped mice (Rhabdomys pumilio) displayed temporal social flexibility, living solitarily in years when population density was low but in groups in years when population density was high. Building on this temporal variation, we now tested whether geographic variation reveals the same pattern. We studied 6 populations in discrete geographical locations simultaneously, predicting more solitary living in populations with lower population density. Population density correlated significantly with the percentage of striped mice living in groups whereas other (environmental) factors were not significant. Moreover, some individuals dispersed over unoccupied habitats between these populations, switching from group to solitary living. Geographic variation in population density could make social flexibility adaptive because it allows individuals to respond quickly to the prevailing conditions they experience post dispersal. Our results suggest that geographic variation drives the evolution of social flexibility in our metapopulation of striped mice, causing intra-specific variation in its social organization, which might also be important in other species, especially in species with a fast life history. Populations of the same species can differ in their social organization. It has often been assumed that this is due to differences in population density. We studied 6 populations of the African striped mice, showing that more mice were solitary living when population density was low. Thus, we demonstrated that population differences in social organization were due to differences in population density.

中文翻译：

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社会组织的地理种内变异由人口密度驱动

社会灵活性使个人能够在集体生活和独居生活之间切换，并建议适应不同的环境。之前对不同物种的几项研究比较了两个种群，并假设观察到的社会组织差异是由于种群密度的差异，但缺乏必要的样本量来检验这一预测。在之前的一项为期 8 年的长期研究中，我们发现一群非洲条纹小鼠 (Rhabdomys pumilio) 表现出暂时的社会灵活性，在人口密度低的年份单独生活，但在人口密度高的年份成群结队。基于这种时间变化，我们现在测试地理变化是否显示相同的模式。我们同时研究了离散地理位置的 6 个种群，预测在人口密度较低的人群中会有更多的孤独生活。种群密度与生活在群体中的条纹小鼠的百分比显着相关，而其他（环境）因素不显着。此外，一些个体分散在这些种群之间的无人居住的栖息地，从群体转变为独居。人口密度的地理变化可以使社会灵活性具有适应性，因为它允许个人对他们在分散后所经历的普遍条件做出快速反应。我们的研究结果表明，地理变异推动了我们条纹小鼠群落社会灵活性的进化，导致其社会组织的种内变异，这在其他物种中可能也很重要，尤其是在具有快速生活史的物种中。同一物种的种群在社会组织方面可能有所不同。人们通常认为这是由于人口密度的差异造成的。我们研究了 6 个非洲条纹老鼠种群，表明当种群密度低时，更多的老鼠是单独生活的。因此，我们证明了社会组织中的人口差异是由于人口密度的差异。