Inclusive fitness theory predicts that the sex investment ratio should be female biased in social insects with haplodiploidy-generated relatedness asymmetry (between females and males and also among females). However, this ratio should become male biased if related females are competing with each other for resources, as it is predicted by local resource competition hypothesis. This specific situation is expected to occur in ant species that reproduce by fission, where young queens leave their mother colonies on foot to found daughter colonies. We tested this idea using the ant Cataglyphis tartessica in Doñana National Park (Spain). This species is monogynous (colonies headed by a single queen), monandrous (queen mate with only one male), and reproduces by fission. Given the similarity between foraging and colony fission distances in this species, a strong local competition for resources should be expected between mother and daughter colonies. In this study, we considered investment in females the sum of the investment in gynes (virgin queens) plus the investment in the worker force that leaves with them to found a new colony. Our results show a male-biased sex investment ratio in C. tartessica of 1:8 (numerical ratio gynes/males 1:56), suggesting queen control over sexual production. In addition, we found that, during its reproductive period, this species exhibits split sex (gyne-male) production as well as split male-worker production, without any evidence of variation in relatedness asymmetry between its colonies, at the population level. An interaction between local resources competition and colony size could explain our results.

中文翻译：

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裂变蚂蚁 Cataglyphis tartessica 的性别投入比和分裂性别比

包容性适应理论预测，在具有单倍二倍体产生的相关性不对称（雌性和雄性之间以及雌性之间）的社会昆虫中，性别投资比例应该是女性偏向的。然而，如果相关的女性为了资源而相互竞争，这个比例应该会变成男性偏向，正如本地资源竞争假设所预测的那样。这种特殊情况预计会发生在通过裂变繁殖的蚂蚁物种中，在这种情况下，年轻的蚁后会步行离开它们的母蚁群去建立子蚁群。我们在多纳纳国家公园（西班牙）使用蚂蚁 Cataglyphis tartessica 测试了这个想法。这个物种是一夫一妻制的（由一个女王领导的殖民地），单一的（女王配偶只有一个雄性），并通过裂变繁殖。鉴于该物种的觅食距离和群体裂变距离之间的相似性，母女殖民地之间应该会出现激烈的当地资源竞争。在这项研究中，我们考虑了对雌性的投资是对雌性（处女皇后）的投资加上对与它们一起离开以建立新殖民地的工人队伍的投资的总和。我们的结果显示，C. tartessica 的雄性性投资比率为 1:8（雌性/雄性数值比为 1:56），表明蜂后控制了性生产。此外，我们发现，在其繁殖期，该物种在种群水平上表现出分裂的性别（雌性-雄性）生产以及分裂的雄性-工人生产，没有任何证据表明其殖民地之间的相关性不对称存在变化。本地资源竞争和殖民地规模之间的相互作用可以解释我们的结果。