Data from: Variation in growth of Damaraland mole-rats is explained by competition rather than by functional specialisation for different tasks

In some eusocial insect societies, adaptation to the division of labour results in multimodal size variation among workers. It has been suggested that variation in size and growth among non-breeders in naked and Damaraland mole-rats may similarly reflect functional divergence associated with different cooperative tasks. However, it is unclear whether individual growth rates are multimodally distributed (as would be expected if variation in growth is associated with specialisation for different tasks) or whether variation in growth is unimodally distributed, and is related to differences in the social and physical environment (as would be predicted if there are individual differences in growth but no discrete differences in developmental pathways). Here we show that growth trajectories of non-breeding Damaraland mole-rats vary widely, and that their distribution is unimodal, contrary to the suggestion that variation in growth is the result of differentiation into discrete castes. Though there is no evidence of discrete variation in growth, social factors appear to exert important effects on growth rates and age-specific size, which are both reduced in large social groups.

在部分真社会性昆虫社会（eusocial insect society）中，对劳动分工（division of labour）的适应使得工蚁间出现多峰体型变异（multimodal size variation）。有观点提出，裸鼹鼠与达马拉兰鼹鼠的非繁殖个体间的体型与生长差异，或许同样反映了与不同合作任务相关的功能分化（functional divergence）。然而目前仍未明确两种潜在情形：其一，个体生长速率是否呈多峰分布（multimodally distributed，若生长差异与不同任务的特化相关，则该分布模式符合预期）；其二，生长差异是否为单峰分布（unimodally distributed），且与社会及物理环境的差异相关（若个体间仅存在生长量的差异，而发育路径（developmental pathways）无离散分化，则该模式符合预测）。本研究结果显示，达马拉兰鼹鼠非繁殖个体的生长轨迹（growth trajectories）存在广泛差异，且其分布呈单峰模式，这与"生长差异源于离散品级分化"的观点相悖。尽管未发现生长存在离散变异的证据，但社会因素似乎对生长速率与年龄特异性体型（age-specific size）具有重要影响：在大型社会群体中，这两项指标均会降低。