Obligate mutualistic symbioses rely on mechanisms that secure host-symbiont commitments to maximize host benefits and prevent symbiont cheating. Previous studies showed that somatic incompatibilities correlate with neutral-marker-based genetic distances between fungal symbionts of Panamanian Acromyrmex leaf-cutting ants, but the extent to which this relationship applies more generally remained unclear. Here we showed that genetic distances accurately predicted somatic incompatibility for Acromyrmex echinatior symbionts irrespective of whether neutral microsatellites or AFLP markers were used, but that such correlations were weaker or absent in sympatric Atta colombica colonies. Further analysis showed that the symbiont clades maintained by A. echinatior and A. colombica were likely to represent separate gene pools, so that neutral markers were unlikely to be similarly correlated with incompatibility loci that have experienced different selection regimes. We suggest that evolutionarily derived claustral colony founding by Atta queens may have removed selection for strong incompatibility in Atta fungi, as this condition makes the likelihood of symbiont swaps much lower than in Acromyrmex, where incipient nests stay open because queens have to forage until the first workers emerge.

强制共生共生依赖于确保宿主-共生承诺的机制，以最大化宿主利益并防止共生作弊。先前的研究表明，体细胞不相容性与巴拿马Acromyrmex 切叶蚂蚁的真菌共生体之间基于中性标记的遗传距离相关，但这种关系在多大程度上更普遍地适用仍不清楚。在这里，我们表明，无论是否使用中性微卫星或 AFLP 标记，遗传距离都能准确预测Acromyrmex echinatior共生体的体细胞不相容性，但这种相关性在同域Atta colombica菌落中较弱或不存在。进一步的分析表明，共生进化枝由A. echinatior和A. colombica可能代表不同的基因库，因此中性标记不太可能与经历不同选择机制的不相容性基因座类似地相关。我们认为，由Atta蜂王建立的进化衍生的 claustral 菌落可能已经消除了对Atta真菌强烈不相容性的选择，因为这种情况使得共生体互换的可能性远低于Acromyrmex 中的可能性，在Acromyrmex 中，初期的巢穴保持开放，因为蜂后必须觅食直到第一次工人出现。