Taxonomic delineation of four Zygophyllum simplex L. (Zygophyllaceae) morphotypes using morphoanatomical, molecular (SCoT) and chemotaxonomic evidence

Abstract

BACKGROUND: This study presents a comprehensive taxonomic adjustment of Zygophyllum simplex (L.) four constituent varieties in Egypt, integrating morphological, anatomical, palynological, molecular, and phytochemical analyses to evaluate their infraspecific differentiation. Samples were collected from the eastern part of Egypt and subjected to detailed morphological, anatomical, and palynological analyses with SCoT molecular genotyping and HPLC phytochemical profiling. RESULTS: Four distinct morphological groups (informally designated as "cylindrica", "retusa", "orbicularis", and "lanceolata") were distinguished by significant differences in growth habit, leaf and stem anatomy, floral morphology, and fruit architecture. SCoT molecular marker analysis revealed a genetic similarity range of 0.825-0.881, with phylogenetic clustering strongly compatible with the morpho-anatomical groupings. HPLC profiling further identified group-specific accumulation patterns of key phenolic and flavonoid compounds, such as chlorogenic acid and catechin. While palynological analysis showed limited diagnostic value, the collective data from multiple disciplines provide robust evidence for the recognition of these four distinct morphotypes. CONCLUSIONS: Morphological, anatomical, and fruit architectural traits, together with group-specific phytochemical profiles and SCoT molecular markers, provided robust evidence for the differentiation of four distinct morphotypes within the Z. simplex complex. However, given the moderate resolution of SCoT markers (37.77% polymorphism), formal varietal status is not proposed at this stage. We recommend that future studies employ higher-resolution molecular approaches, such as single nucleotide polymorphism (SNP) analysis and DNA barcoding, to validate whether these morphotypes represent genetically distinct and reproductively coherent varieties. Pending such validation, these taxa should be treated as morphotypes, thereby establishing a preliminary integrative framework for their identification.