Fire Ant Colony Fitness and Worker Polymorphism

火蚁群适应度与工蚁多态性达尔文认为群居昆虫中不育工蜂的存在是对他的自然选择进化论的挑战。 毕竟，一个没有繁殖的个体的特征怎么可能遗传给下一代？ 达尔文和他的追随者普遍接受的答案是，殖民地是自然选择作用的生殖单位。 因此，无论工蚁的性状如何，只要能让殖民地在下一代中产生更多的新蚁群，自然选择就会青睐它们。 绝大多数蚂蚁物种只有两种生理等级：繁殖个体（蚁后）和大小和形状单一的不育工蚁。在大约15%的蚂蚁物种中，工蚁的大小和形状有很大的差异（重量差异高达1000倍）。 这种所谓的工人多态性，总是与工人种姓内部的进一步分工有关。 长期以来，人们一直认为工蜂多态性通过提高群体效率而使殖民地受益，因此节省下来的资金可以投资于额外的繁殖动物，提高群体适应性（有性生产）。几个测试的替代品的健身（觅食，育雏饲养等）已经产生了模棱两可的结果，但这些替代物都与性生产没有紧密联系。 从来没有一个直接的测试的影响，工人多态性的群体健身，也就是说，对生产性。 拟议的实验将是第一次直接测试工人多态性的价值，以殖民地的健身。 在一个大的，2年的现场实验的火蚁，红火蚁，工人puerestrium选定的大小将被转移到殖民地之间，使一组殖民地将提高在大工人，另一个在小工人，第三个将作为不变的控制，和第四个不受干扰的控制。 这些实验群体的殖民地适合度将通过使用帐篷诱捕器收集总的年度性生产来测量。影响（如果有的话）改变工人的多态性可能是直接通过参与大型工人在性生产，或间接通过改变领土防御或觅食。 因此，还将监测食物的数量和质量以及领土面积，并与对照组进行比较。 这些实地实验的结果将补充一系列的实验室实验，将测试每一个可能的链接（直接，食物，领土）之间的工人多态性和殖民地的性生产。 这些结果将解决进化生物学和社会昆虫生物学非常感兴趣的基本问题。

Fire ant colony fitness and worker polymorphismWalter R. TschinkelProject Summary Darwin considered the existence of a sterile worker caste in social insects to be a challenge to his theory of evolution by natural selection. After all, how could the traits of an individual that did not reproduce be passed on to the next generation? The answer that Darwin and his followers have generally accepted is that the colony is the reproductive unit on which natural selection acts. Thus, whatever worker traits allowed the colony to place more new colonies in the next generation would be favored by natural selection. The great majority of ant species have only two physical castes: reproductive individuals (queens), and more-or-less sterile workers of a single size and shape. In about 15% of ant species, the workers are present in a great range of sizes (up to 1000-fold difference in weight) and shapes. Such worker polymorphism, as it is called, is always associated with further division of labor within the worker caste. It has long been assumed that worker polymorphism benefits the colony by increasing colony efficiency, so that the savings can be invested in additional reproductives, enhancing colony fitness (sexual production). Several tests of surrogates for fitness (foraging, brood-rearing, etc.) have yielded equivocal results, but none of these surrogates are tightly linked to sexual production. There has never been a direct test of the effects of worker polymorphism on colony fitness, that is, on the production of sexuals. The proposed experiments will be the first direct test of the value of worker polymorphism to colony fitness. In a large, 2-yr field experiment on the fire ant, Solenopsis invicta, worker pupae of selected sizes will be transferred among colonies such that one set of colonies will be enhanced in large workers, another in small workers, a third will serve as unaltered control, and a fourth as undisturbed control. The colony fitness of these experimental colonies will be measured by collecting the total annual sexual production using tent-traps. Effects (if any) of altering the worker polymorphism might be either direct through involvement of large workers in sexual production, or indirect through altered territorial defense or foraging. Therefore, the food quantity and quality, as well as territory size will also be monitored and compared to controls. The results of these field experiments will be supplemented with a series of laboratory experiments that will test each possible link (direct, food, territory) between worker polymorphism and colony sexual production. The results will address a fundamental issue of great interest to evolutionary biology and social insect biology.