Kümmerli Rolf, Helms Ken R, Keller Laurent
Department of Ecology and Evolution, Biology Building, University of Lausanne, 1015 Lausanne, Switzerland.
Proc Biol Sci. 2005 Sep 7;272(1574):1789-94. doi: 10.1098/rspb.2005.3163.
In polygynous (multiple queens per nest) ants, queen dispersal is often limited with young queens being recruited within the parental colony. This mode of dispersal leads to local resource competition between nestmate queens and is frequently associated with extremely male-biased sex ratios at the population level. The queen-replenishment hypothesis has been recently proposed to explain colony sex ratio investment under such conditions. It predicts that colonies containing many queens (subject to high local resource competition) should only produce males, whereas colonies hosting few queens (reduced or no local resource competition) should produce new queens in addition to males. We experimentally tested this hypothesis in the ant Formica exsecta by manipulating queen number over three consecutive years in 120 colonies of a highly polygynous population. Queens were transferred from 40 colonies into another 40 colonies while queen number was not manipulated in 40 control colonies. Genetic analyses of worker offspring revealed that our treatment significantly changed the number of reproductive queens. The sex ratio of colonies was significantly different between treatments in the third breeding season following the experiment initiation. We found that, as predicted by the queen-replenishment hypothesis, queen removal resulted in a significant increase in the proportion of colonies that produced new queens. These results provide the first experimental evidence for the queen-replenishment hypothesis, which might account for sex ratio specialization in many highly polygynous ant species.
在一夫多妻制（每个蚁巢有多个蚁后的）蚂蚁中，蚁后的扩散通常受到限制，年轻蚁后会在亲代蚁巢内被招募。这种扩散模式导致同巢蚁后之间产生局部资源竞争，并且在种群水平上常常与极度偏雄的性别比例相关。最近有人提出了蚁后补充假说，以解释在这种情况下蚁群的性别比例投资。该假说预测，包含许多蚁后的蚁群（面临高局部资源竞争）应该只产生雄蚁，而蚁后数量少的蚁群（局部资源竞争减少或不存在）除了产生雄蚁外还应该产生新蚁后。我们通过在一个高度一夫多妻制种群的120个蚁群中连续三年操纵蚁后数量，对蚁后补充假说进行了实验检验。将40个蚁群中的蚁后转移到另外40个蚁群中，同时在40个对照蚁群中不操纵蚁后数量。对工蚁后代的基因分析表明，我们的处理显著改变了繁殖蚁后的数量。在实验开始后的第三个繁殖季节，不同处理的蚁群性别比例存在显著差异。我们发现，正如蚁后补充假说所预测的那样，移除蚁后导致产生新蚁后的蚁群比例显著增加。这些结果为蚁后补充假说提供了首个实验证据，该假说可能解释了许多高度一夫多妻制蚂蚁物种的性别比例特化现象。
