Data from: Can social partnerships influence the microbiome? insights from ant farmers and their trophobiont mutualists.

Mutualistic interactions with microbes have played a crucial role in the evolution and ecology of animal hosts. However, it is unclear what factors are most important in influencing particular host-microbe associations. While closely related animal species may have more similar microbiota than distantly related ones due to phylogenetic contingencies, social partnerships with other organisms, such as those in which one animal farms another, may also influence an organism’s symbiotic microbiome. We studied a mutualistic network of Brachymyrmex and Lasius ants farming several honeydew-producing Prociphilus aphids and Rhizoecus mealybugs to test whether the mutualistic microbiomes of these interacting insects are primarily correlated with their phylogeny or with their shared social partnerships. Our results confirm a phylogenetic signal in the microbiomes of aphid and mealybug trophobionts, with each species harboring species-specific endosymbiont strains of Buchnera (aphids), Tremblaya and Sodalis (mealybugs), and Serratia (both mealybugs and aphids) despite being farmed by the same ants. This is likely explained by strict vertical transmission of trophobiont endosymbionts between generations. In contrast, the ants’ microbiome is potentially shaped by their social partnerships, with ants that farm the same trophobionts also sharing strains of sugar-processing Acetobacteraceae bacteria, known from other honeydew-feeding ants and which likely reside extracellularly in the ants’ guts. These ant-microbe associations are arguably more ‘open’ and subject to horizontal transmission or social transmission within ant colonies. These findings suggest that the role of social partnerships in shaping a host’s symbiotic microbiome can be variable, and is likely dependent on how the microbes are transmitted across generations.

与微生物间的互利共生相互作用（mutualistic interactions）在动物宿主的演化与生态进程中发挥了关键作用。然而，目前尚不明确哪些因素对特定宿主-微生物共生关系的影响最为显著。尽管由于系统发育约束（phylogenetic contingencies），亲缘关系较近的动物物种相较于远缘物种，其微生物组更为相似，但与其他生物形成的社会伙伴关系（social partnerships）——例如某一动物饲养另一生物的共生模式——同样可能影响宿主的共生微生物组（symbiotic microbiome）。本研究以短角蚁属（Brachymyrmex）与毛蚁属（Lasius）的互利共生网络为研究对象，这类蚂蚁会饲养多种产蜜露的漆蚜属（Prociphilus）蚜虫及根粉蚧属（Rhizoecus）粉蚧，旨在探究这些互作昆虫的共生微生物组，主要与其系统发育相关，还是与其共享的社会伙伴关系相关。研究结果证实，蚜虫与粉蚧的营养共生体（trophobionts）微生物组存在系统发育信号：尽管均由同种蚂蚁饲养，但各物种分别携带物种特异性的内共生菌株（endosymbiont strains），其中蚜虫的内共生菌为布赫纳菌属（Buchnera），粉蚧的内共生菌为特雷布莱亚菌属（Tremblaya）与索氏菌属（Sodalis），而沙雷菌属（Serratia）则同时存在于粉蚧与蚜虫体内。这一现象大概率可通过营养共生体内共生菌在代际间的严格垂直传播加以解释。与之形成对比的是，蚂蚁的微生物组可能受其社会伙伴关系的塑造：饲养相同营养共生体的蚂蚁，会共享一类参与糖代谢的醋杆菌科（Acetobacteraceae）菌株——这类细菌已在其他以蜜露为食的蚂蚁中被发现，且大概率定殖于蚂蚁肠道的细胞外区域。这类蚂蚁-微生物共生关系显然更为“开放”，易受到蚁群内部的水平传播（horizontal transmission）或社会传播（social transmission）的影响。上述研究结果表明，社会伙伴关系在塑造宿主共生微生物组中的作用存在差异，且大概率取决于微生物在代际间的传播方式。