Schwander Tanja, Keller Laurent, Cahan Sara Helms
Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
Mol Ecol. 2007 Sep;16(17):3533-43. doi: 10.1111/j.1365-294X.2007.03407.x.
Some populations of Pogonomyrmex harvester ants comprise pairs of highly differentiated lineages with queens mating at random with several males of their own and of the alternate lineage. These queens produce two types of diploid offspring, those fertilized by males of the queens' lineage which develop into new queens and those fertilized by males of the other lineage which mostly develop into functionally sterile workers. This unusual mode of genetic caste determination has been found in 26 populations and a total of four lineage pairs (F(1)-F(2), G(1)-G(2), H(1)-H(2) and J(1)-J(2)) have been described in these populations. Despite the fact that a few interlineage queens are produced, previous studies revealed that there is a complete lack of genetic introgression between lineages. Here we quantify the proportion of interlineage queens produced in each of the four lineage pairs and determine the fate of these queens. In the F(1)-F(2), G(1)-G(2) and H(1)-H(2) lineage pairs, interlineage queens were produced by a minority of colonies. These colonies exclusively produced interlineage queens and workers, suggesting that interlineage eggs can develop into queens in these three pairs of lineages in the absence of competition with pure-lineage brood. An analysis of three key stages of the colony life cycle revealed that colonies headed by interlineage queens failed to grow sufficiently to produce reproductive individuals. In laboratory comparisons, interlineage queens produced fewer viable eggs, with the effect that they raised fewer workers and lost more weight per worker produced than pure-lineage queens. In the J(1)-J(2) lineage pair, we did not find a single interlineage queen, raising the possibility that interlineage eggs have completely lost the ability to develop into queens in this lineage pair. Hence, two distinct mechanisms seem to account for the complete lack of between-lineage gene flow in the F(1)-F(2), G(1)-G(2), H(1)-H(2) and J(1)-J(2) lineage pairs.
部分收获蚁种群由高度分化的谱系对组成，蚁后会随机与来自自身谱系以及另一谱系的几只雄蚁交配。这些蚁后会产生两种二倍体后代，一种是由本谱系雄蚁受精的，发育成新的蚁后；另一种是由另一谱系雄蚁受精的，大多发育成功能不育的工蚁。这种不寻常的基因等级决定模式在26个种群中被发现，在这些种群中总共描述了四对谱系（F(1)-F(2)、G(1)-G(2)、H(1)-H(2)和J(1)-J(2)）。尽管会产生少数跨谱系蚁后，但先前的研究表明谱系之间完全不存在基因渗入。在此，我们量化了四对谱系中每一对产生的跨谱系蚁后的比例，并确定这些蚁后的命运。在F(1)-F(2)、G(1)-G(2)和H(1)-H(2)谱系对中，少数蚁群会产生跨谱系蚁后。这些蚁群只产生跨谱系蚁后和工蚁，这表明在没有与纯谱系幼虫竞争的情况下，跨谱系卵在这三对谱系中能够发育成蚁后。对蚁群生命周期三个关键阶段的分析表明，由跨谱系蚁后领导的蚁群未能充分发展以产生有繁殖能力的个体。在实验室比较中，跨谱系蚁后产生的可存活卵较少，结果是与纯谱系蚁后相比，它们培育的工蚁更少，且每培育一只工蚁体重损失更多。在J(1)-J(2)谱系对中，我们没有发现一只跨谱系蚁后，这增加了跨谱系卵在这一谱系对中完全丧失发育成蚁后能力的可能性。因此，似乎有两种不同的机制导致了F(1)-F(2)、G(1)-G(2)、H(1)-H(2)和J(1)-J(2)谱系对之间完全缺乏谱系间基因流动。
