How introgression affects leaf endophytic fungi: higher diversity but lower co-occurrence network complexity

Plant-leaf endophytic fungi mutualism is essential for plants to adapt to adverse environments. Though introgression has been extensively studied in many plants, the underlying effects of introgression on fungi-driven adaptability still remain unanswered. Here, we performed landscape-scale sampling of natural populations across its typical distribution range in China to disentangle how introgression effects endophytic fungal community within oak leaves. Our results showed that fungal diversity was decreased while fungal co-occurrence network complexity was increased with increasing introgression index, reflecting a “dual adaptation strategy” to respond to environmental challenges. This pattern was also linked to metacommunity: the lowest diversity occurred in metacommunity that characterized by the lowest mean annual temperature and annual precipitate, whereas the highest fungal network complexity appeared in metacommunity that had the highest mean annual temperature and optimal annual precipitate. Importantly, the differential metabolite intensities (e.g., organoheterocyclic compounds, and organoheterocyclic compounds) and climate factors mediated the leaf endophytic fungi-driven adaptability of oak trees. This work not only advances our understanding of plant-microbe interactions in the context of evolutionary ecology but also provides insight into the importance of fungal community restructuring in facilitating plant adaptation to environmental change.