Chiang Mai Journal of Science

Mangrove ecosystems support complex microbial symbioses that enhance plant growth, stress tolerance, and ecosystem resilience, yet endophytic fungal diversity and functional organization remain poorly understood in the Indo-Pacific region, limiting their application in mangrove conservation and restoration. Using the Batticaloa Lagoon mangrove ecosystem in Eastern Sri Lanka as a model system, this study investigated the taxonomic diversity, community structure, and inferred functional trait distribution (based on in vitro analyses of isolated endophytes) of culturable putative endophytic fungi associated with Avicennia marina (Forssk.) Vierh. and Excoecaria agallocha L. across leaf, stem, and root tissues. Endophytic fungal communities were hierarchically structured by host identity and tissue-level environmental filtering. Root assemblages functioned as primary reservoirs of taxonomic and inferred functional diversity. A total of 45 putative fungal taxa representing 39 genera were isolated from 7,800 tissue segments and identified conservatively, primarily at the genus level. Avicennia marina supported significantly higher species richness and colonization frequency than E. agallocha, with distinct host-specific dominance patterns. Fusarium sp. 1 and Neofusicoccum sp. dominated A. marina, whereas Phyllosticta sp. 1, Penicillium sp., and Aspergillus sp. 1 dominated E. agallocha. Alpha diversity analyses indicated higher richness but lower evenness in A. marina, while E. agallocha harbored fewer but more evenly distributed taxa. Beta diversity analyses demonstrated substantial turnover between hosts and tissue types, with root communities exhibiting strong host specificity. In vitro functional traits of fungal isolates varied strongly: approximately half showed medium-to-high IAA production, one-third exhibited phosphate solubilization, and salt tolerance were widespread. Trait-based analyses (community-weighted means and indicator values), identified root tissues as hotspots of functional potential enriched in nutrient-mobilizing and stress-tolerance traits, as assessed by in vitro assays. These findings, which are restricted to the culturable fraction of the mycobiota, provided baseline data for an underexplored mangrove system and highlight the importance of conserving endophytic diversity to enhance mangrove conservation and restoration strategies, pending in planta and field validation of the functional traits identified.