Linking genome size to life form and community structure in a semi-natural landscape from Northeast India.

Northeast India, a global biodiversity hotspot, harbors exceptional plant diversity within the Indo-Burma region. This study provides the first comprehensive integration of floristic, ecological, and genomic analyses of angiosperm diversity in North Guwahati, Assam, using the Indian Institute of Technology Guwahati campus as a model semi-natural landscape. Systematic year-long surveys recorded 434 angiosperm species belonging to 312 genera and 101 families, including 70 trees, 86 shrubs, and 244 herbs (with 31 climbers and a few aquatics). Poaceae was the most species-rich family (34 species), followed by Fabaceae (29) and Cyperaceae (26), reflecting typical tropical diversity. Spatial analysis revealed strong habitat-specific species distribution, with open plains supporting the highest diversity (206 species) and forest edges harboring rare taxa. Community structure across four ecological zones showed significant spatial heterogeneity, with Zone 1 having the highest Shannon-Wiener diversity (H' = 4.084) and Zone 4 the highest evenness (E = 0.905). Nuclear DNA content (2C values) was estimated via flow cytometry for 110 species, contributing 58 novel genome size records and revealing a 98-fold variation (0.43-42.5 pg). Monocots had significantly larger genomes than dicots (4.79 vs. 1.63 pg, p < 0.001), and ecological trends showed a progressive increase in genome size from herbaceous (1.93 pg) to woody forms (2.50 pg), supporting the large genome constraint hypothesis. GIS mapping integrated taxonomic, ecological, and genomic data, uncovering spatial patterns in diversity and genome evolution. region. This comprehensive framework provides a crucial foundation for assessing biodiversity and guiding conservation efforts in this ecologically important region.