Data from: Clinal variation in colony breeding structure and level of inbreeding in the subterranean termites Reticulitermes flavipes and R. grassei

Social insects exhibit remarkable variation in their colony breeding structures, both within and among species. Ecological factors are believed to be important in shaping reproductive traits of social insect colonies, yet there is little information linking specific environmental variables with differences in breeding structure. Subterranean termites (Rhinotermitidae) show exceptional variation in colony breeding structure, differing in the number of reproductives and degree of inbreeding; colonies can be simple families headed by a single pair of monogamous reproductives (king and queen) or they can be extended families headed by multiple inbreeding neotenic reproductives (wingless individuals). Using microsatellite markers, we characterized colony breeding structure and levels of inbreeding in populations over large parts of the range of the subterranean termites Reticulitermes flavipes in the USA and R. grassei in Europe. Combining these new data with previous results on populations of both species, we found that latitude had a strong effect on the proportion of extended-family colonies in R. flavipes and on levels of inbreeding in both species. We examined the effect of several environmental variables that vary latitudinally; while the degree of inbreeding was greatest in cool, moist habitats in both species, seasonality affected the species differently. Inbreeding in R. flavipes was most strongly associated with climatic variables (mean annual temperature and seasonality), whereas nonclimatic variables, including the availability of wood substrate and soil composition, were important predictors of inbreeding in R. grassei. These results are the first showing that termite breeding structure is shaped by local environmental factors and that species can vary in their responses to these factors.

社会性昆虫在物种内部与跨物种间均展现出巢群繁殖结构的显著多样性。尽管生态因子被认为是塑造社会性昆虫巢群繁殖性状的关键因素，但目前鲜有研究能将特定环境变量与巢群繁殖结构的差异建立明确关联。鼻白蚁科（Rhinotermitidae）的地下白蚁，其巢群繁殖结构变异尤为突出：繁殖者的数量与近交程度均存在显著差异，巢群既可由单一对单配制繁殖者（蚁王与蚁后）统领的简单家族构成，也可由多只近交新型繁殖者（无翅个体）统领的扩展家族组成。本研究利用微卫星标记（microsatellite markers），对分布于美国大部分区域的黄肢散白蚁（Reticulitermes flavipes）以及欧洲的格氏散白蚁（R. grassei）的种群巢群繁殖结构与近交水平进行了系统表征。结合本次新生成的数据与此前针对两个物种种群的研究结果，我们发现纬度对黄肢散白蚁的扩展家族巢群占比，以及两个物种的近交水平均具有显著调控作用。我们进一步分析了多个随纬度梯度变化的环境变量的影响：尽管两个物种的近交程度在凉爽湿润的生境中均达到峰值，但季节节律对两个物种的影响模式存在显著差异。黄肢散白蚁的近交程度与气候变量（年平均温度及季节节律）关联最为紧密，而格氏散白蚁的近交水平则主要受非气候变量调控，包括木质基质可用性与土壤组成。本研究首次证实，白蚁的繁殖结构受局域环境因子塑造，且不同物种对这些环境因子的响应存在分化。