Abstract

Endophytic Microbial Communities Of Congeneric Native and Invasive Lantana
(Verbenaceae) Species in India
ABSTRACT
Subhikshaa Bagavathiappan, Ph.D.
Concordia University, 2025
Plant invasion has emerged as a major focus of research in ecology and invasion biology as it poses
a serious threat to the integrity of natural ecosystems by displacing native plant communities and
promoting the formation of monocultures in newly colonized habitats. Although numerous
theories have been advanced to explain the success of invasive species, the role of plant-microbe
interactions remains as one of the most understudied aspects of invasion biology. Endophytic
microbes play an important role in maintaining plant health, adaptability, and ecological
interactions. In this study, I investigated the diversity, composition, and abiotic stress tolerance of
bacterial and fungal endophytes associated with Lantana camara, an invasive plant species, and
Lantana indica, its native congener, co-occurring in India. Using culture-independent amplicon
sequencing (16S rRNA and ITS region of nuclear rDNA), culture-dependent isolation methods
and abiotic stress tolerance assays, I examined the invasive and native plants to identify their
distinct bacterial and fungal communities and the tolerance of fungi to abiotic stressors. Amplicon
sequencing demonstrated Ascomycota to be the dominant phyla and Talaromyces as the dominant
fungal genus in both L. camara and L.indica, while the bacterial communities were dominated by
the family Clostridiaceae in L. camara and Pseudomonadaceae in L. indica. The native plants
showed higher bacterial diversity and evenness compared to invasive plants suggesting a longterm
adaptation to local biotic and abiotic conditions, whereas fungal communities showed no
difference emphasizing that the endophytic fungi share similar community composition and
functional adaptation. Culture dependent isolation of endophytic fungi revealed Ascomycota to be
the dominant phyla. Both culture dependent and culture independent methods were compared to
show how they can complement each other due to various bias adhered to these techniques. Abiotic
stress tolerance assays on selected fungal isolates demonstrated species specific stress tolerance.
Aspergillus spp. showing high salinity (2.5M NaCl) and drought (15% PEG) tolerance, while
Macrophomina phaseolina remained viable at 45 °C. These results suggest that endophytes can
potentially support host survival under abiotic stress, likely facilitating plant growth. Overall, the
thesis highlights that the endophytic communities differ between invasive and native Lantana
species, and specific endophytes show stress resilience in vitro. Understanding such microbial
associations is essential in uncovering mechanisms underlying plant adaptation and invasion
process.