Multilevel selection with kin and non-kin groups, experimental results with Japanese quail (Coturnix japonica)

An experiment was conducted comparing multilevel selection in Japanese quail for 43 days weight and survival with birds housed in either kin (K) or random (R) groups. Multilevel selection significantly reduced mortality (6.6% K vs. 8.5% R) and increased weight (1.30 g/MG K vs. 0.13 g/MG R) resulting in response an order of magnitude greater with Kin than Random. Thus multilevel selection was effective in reducing detrimental social interactions, which contributed to improved weight gain. The observed rates of response did not differ significantly from expected, demonstrating that current theory is adequate to explain multilevel selection response. Based on estimated genetic parameters, group selection would always be superior to any other combination of multilevel selection. Further, near optimal results could be attained using multilevel selection if 20% of the weight was on the group component regardless of group composition. Thus in nature the conditions for multilevel selection to be effective in bringing about social change maybe common. In terms of a sustainability of breeding programs, multilevel selection is easy to implement and is expected to give near optimal responses with reduced rates of inbreeding as compared to group selection, the only requirement is that animals be housed in kin groups.

本实验以日本鹌鹑（Japanese quail）为研究材料，针对其43日龄体重与存活表现，比较了不同饲养分组下的多水平选择（multilevel selection）效应：鹌鹑分别被饲养于亲缘组（kin group，K）或随机组（random group，R）中。实验结果表明，多水平选择可显著降低鹌鹑死亡率（K组6.6% vs. R组8.5%），并提升其体重增长水平（K组为1.30 g/MG，R组为0.13 g/MG），其选择响应较随机组高出一个数量级。由此可见，多水平选择可有效抑制有害社会互动，进而促进体重增长。观测得到的选择响应速率与理论预期值无显著差异，表明现有理论足以阐释多水平选择的响应机制。基于估算得到的遗传参数，群体选择（group selection）始终优于多水平选择的其他组合模式。此外，若将20%的选择权重赋予群体组分，无论群体组成如何，采用多水平选择即可获得接近最优的选择效果。因此在自然环境中，多水平选择可有效介导社会性状改变的条件可能普遍存在。就育种项目的可持续性而言，多水平选择易于实施，且相较于群体选择，其可在降低近交速率的同时获得接近最优的选择响应，唯一的实施要求是将鹌鹑饲养于亲缘分组中。