## 4 Discussion
### Volatile-Mediated Plant-Microbe Interactions among the Sphingeticola Species  
Plant leaves emit VOCs that can influence the composition of their phyllosphere microbial communities. Compounds like terpenoids, phenylpropanoids and phenylides have antimicrobial properties and can inhibit colonization [55; 56]. _S. trilobata_ produces high amounts of terpenoids with insecticidal and antimicrobial activity, which may contribute to its lower microbial diversity relative to the other _Sphagneticola_ groups.  
The VOCs from _S. trilobata_ could interfere with native plants and microbes, enabling the formation of single-species communities. Antifungal VOCs may also allow _S. trilobata_ to avoid native pathogens, facilitating invasion success. However, microbial communities can reciprocally shape the production of plant VOCs. For example, _Bacteroides_, _Bacillus_ and _Methylobacterium-Methylurbrum_, found on raspberries, produce VOCs that increase pest/disease resistance [57; 58].  
In this study, _Methylobacterium-Methylorbrum_ was most abundant across all _Sphagneticola_ groups, especially the hybrid. This suggests the hybrid, not just _S. trilobata_, may possess strong chemical effects that reduce suitable habitat for native species. Plant-microbe interactions and their shared chemical mediators warrant further study as determinants of community structure and potential drivers of species invasion.  
The reciprocal relationships between plants, microbes and their volatile signals are complex but ecologically significant. While terpenoid-rich _S. trilobata_ may chemically inhibit competitors to dominate communities, associated microbes like _M. methylorbrum_ could simultaneously enhance its defenses and stress tolerance in new ranges. However, whether the high abundance of _M. methylorbrum_ provides benefits, and what microbial-derived VOCs are involved, requires experimental confirmation. The hybrid's combined volatile chemistry and microbial profile may represent an intermediate or novel state that similarly influences community assembly and species distributions.  
Overall, volatile-mediated plant-microbe interactions deserve greater consideration as mechanisms not only promoting but also potentially limiting or regulating the spread of invasive species outside their native ranges. _S. trilobata_'s chemical effects on and associations with other organisms likely depend on attributes of both its new and ancestral environments, as well as its resident microbiota. The hybrid's unique characteristics may also derive from a combination of introduced and native influences that shape its biological and ecological relationships in a distinct manner. Further work could explore how terpenoid profiles, microbial communities and their interactive VOCs differ quantitatively and qualitatively between these groups across native and introduced populations. Manipulative experiments are also needed to determine the causal roles of plant and microbial volatiles in community dynamics, species coexistence and habitat generation or loss. By integrating chemical and biological approaches, deeper insights may be gained into the complex factorsunderlying plant invasion, competitive exclusion of natives, and conservation of diversity even between closely-related species.