In disease ecology, pathogen transmission among conspecific versus heterospecific hosts is known to shape pathogen specialization and virulence, but we do not yet know if similar effects occur at the microbiome level. We tested this idea by experimentally passaging leaf-associated microbiomes either within conspecific or across heterospecific plant hosts. Although conspecific transmission results in persistent host-filtering effects and more within-microbiome network connections, heterospecific transmission results in weaker host-filtering effects but higher levels of interconnectivity. When transplanted onto novel plants, heterospecific lines are less differentiated by host species than conspecific lines, suggesting a shift toward microbiome generalism. Finally, conspecific lines from tomato exhibit a competitive advantage on tomato hosts against those passaged on bean or pepper, suggesting microbiome-level host specialization. Overall, we find that transmission mode and previous host history shape microbiome diversity, with repeated conspecific transmission driving microbiome specialization and repeated heterospecific transmission promoting microbiome generalism.

在疾病生态学中，已知同种与异种宿主之间的病原体传播会影响病原体的特化和毒力，但我们尚不知道在微生物组水平上是否会发生类似的影响。我们通过在同种植物宿主内或异种植物宿主之间实验传代与叶子相关的微生物组来测试这个想法。虽然同种传播会导致持久的宿主过滤效应和更多的微生物组内网络连接，但异种传播会导致宿主过滤效应较弱，但互连性水平较高。当移植到新植物上时，异种品系因宿主物种而产生的差异小于同种品系，这表明微生物组普遍性的转变。最后，来自番茄的同种系在番茄宿主上与在豆类或辣椒上传代的系相比表现出竞争优势，这表明微生物组水平的宿主专业化。总体而言，我们发现传播模式和先前的宿主历史塑造了微生物组的多样性，重复的同种传播推动了微生物组的专业化，重复的异种传播促进了微生物组的普遍化。