Schwander Tanja, Cahan Sara Helms, Keller Laurent
Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
Mol Ecol. 2007 Jan;16(2):367-87. doi: 10.1111/j.1365-294X.2006.03124.x.
Genetic caste determination has been described in two populations of Pogonomyrmex harvester ants, each comprising a pair of interbreeding lineages. Queens mate with males of their own and of the alternate lineage and produce two types of diploid offspring, those fertilized by males of the queens' lineage which develop into queens and those fertilized by males of the other lineage which develop into workers. Each of the lineages has been shown to be itself of hybrid origin between the species Pogonomyrmex barbatus and Pogonomyrmex rugosus, which both have typical, environmentally determined caste differentiation. In a large scale genetic survey across 35 sites in Arizona, New Mexico and Texas, we found that genetic caste determination associated with pairs of interbreeding lineages occurred frequently (in 26 out of the 35 sites). Overall, we identified eight lineages with genetic caste determination that always co-occurred in the same complementary lineage pairs. Three of the four lineage pairs appear to have a common origin while their relationship with the fourth remains unclear. The level of genetic differentiation among these eight lineages was significantly higher than the differentiation between P. rugosus and P. barbatus, which questions the appropriate taxonomic status of these genetic lineages. In addition to being genetically isolated from one another, all lineages with genetic caste determination were genetically distinct from P. rugosus and P. barbatus, even when colonies of interbreeding lineages co-occurred with colonies of either putative parent at the same site. Such nearly complete reproductive isolation between the lineages and the species with environmental caste determination might prevent the genetic caste determination system to be swept away by gene flow.
在收获蚁属的两个种群中描述了基因决定蚁型现象，每个种群都由一对杂交谱系组成。蚁后与自身谱系和交替谱系的雄蚁交配，产生两种二倍体后代，一种由蚁后谱系的雄蚁受精，发育成蚁后，另一种由其他谱系的雄蚁受精，发育成工蚁。每个谱系都已被证明本身是巴氏收获蚁和粗糙收获蚁这两个物种之间的杂交起源，这两个物种都具有典型的、由环境决定的蚁型分化。在一项对亚利桑那州、新墨西哥州和得克萨斯州35个地点的大规模基因调查中，我们发现与杂交谱系对相关的基因决定蚁型现象频繁出现（35个地点中有26个）。总体而言，我们识别出八个具有基因决定蚁型的谱系，它们总是在相同的互补谱系对中共同出现。四个谱系对中的三个似乎有共同起源，而它们与第四个谱系对的关系仍不清楚。这八个谱系之间的基因分化水平明显高于粗糙收获蚁和巴氏收获蚁之间的分化，这对这些基因谱系的适当分类地位提出了疑问。除了彼此在基因上相互隔离外，所有具有基因决定蚁型的谱系在基因上都与粗糙收获蚁和巴氏收获蚁不同，即使杂交谱系的蚁群与任一假定亲本的蚁群在同一地点同时出现。这些谱系与具有环境决定蚁型的物种之间如此近乎完全的生殖隔离可能会阻止基因决定蚁型系统被基因流淘汰。
