Macro‐ and micromorphological insights into Iranian Onobrychis subgenus Onobrychis Miller (Fabaceae): exploring fruit traits for taxonomic clarity

This study provides a comprehensive examination of fruit morphology and micromorphology characteristics of 28 populations of Onobrychis subgenus Onobrychis taxa from Iran, using both light and scanning electron microscopy. For each trait, 25 replicates were analyzed, encompassing a wide range of qualitative and quantitative traits. Data were processed using PAST and SPSS software. All examined taxa possessed one‐segmented fruits with a similar epidermal structure. Hilum inward bend and bilateral symmetry showed limited variation, whereas fruit color ranged from pale green to various shades of brown and cream. A variety of fruit shapes was observed, with the half‐circular form being the most common. Most taxa exhibited variation in margin type and epidermal outgrowths, predominantly spinose, although some lacked these structures entirely. Notably, Onobrychis altissima population 1 possessed a smooth (entire) fruit margin. Principal component analysis (PCA) revealed that the first two components explained more than 66% of the total variation, and the PCA biplot showed clear differentiation among taxa based on trait combinations. However, hierarchical clustering using the WARD method did not correspond well with the traditional sectional classification proposed in the Flora Iranica and Flora of Iran. Significant infraspecific variation was also detected at both the variety and population levels. This study demonstrates that the examined characters provide limited but valuable taxonomic information within this subgenus. While traits such as hilum morphology and membranous fruit margins are useful for species delimitation, some others – including dorsi‐ventral symmetry, fruit shape, and epidermal configuration – show variability, reducing their reliability at the sectional level. Cluster analyses further reveal incongruence with traditional classifications, supporting the need for taxonomic revision. The observed infraspecific variation suggests ongoing evolutionary divergence. Overall, an integrative approach combining morphological and molecular data is essential for a robust and phylogenetically meaningful classification.