Taxonomic Revision of Genus <i>Ephedra</i> Tourn. ex L. in Egypt with Intra-Gender Diversity in Morphometric Traits and Fatty Acid Composition

The genus <i>Ephedra</i> Tourn. ex L. (Ephedraceae) still exhibits taxonomic complexity that has not yet been resolved. This study aimed to determine the taxonomic identity of the <i>Ephedra</i> species in Egypt and identify the fatty acid profile and its diversity at the gender level as a taxonomic tool for specimens lacking reproductive cones. The current study provides a pioneering approach that distinguishes <i>Ephedra</i> species at the gender level. A total of 120 fresh individuals were collected from 20 locations representing different habitats where <i>Ephedra</i> plants grow in Egypt. In addition, herbarium specimens were deposited in Egyptian herbaria. The studied morphological traits included 30 vegetative characteristics and 72 traits of the reproductive organs of both genders. The fatty acid content was measured using gas–mass chromatography (GC-Mass). The taxonomic revision revealed that the Genus <i>Ephedra</i> was represented in the Egyptian flora by five species, <i>Ephedra alata</i> in section Alatae and <i>E. aphylla</i>, <i>E. ciliata</i>, <i>E. foemina</i>, and <i>E. pachyclada</i> in section <i>Ephedra</i>. South Sinai hosts these five species and represents the center of diversity for this genus in Egypt. The vegetative characteristics were subjected to principal component analysis (PCA), which revealed a distinct separation of the five studied species. Similarly, the cone traits treated by hierarchical clustering revealed intra-gender variations. The taxonomic key was developed based on the morphological traits to distinguish the studied species at the gender level. In total, 51 fatty acids were identified from the studied species and grouped as 18 saturated, 16 monounsaturated, and 17 polyunsaturated fatty acids. In the absence of reproductive cones, the lipid content and fatty acid composition of the vegetative parts displayed significant interspecific and intra-gender variations. Therefore, fatty acids can be used to efficiently identify the studied species when they lack reproductive cones. This study proved the efficacy of a multidisciplinary approach to identify <i>Ephedra</i> species at the gender level and recommends this trend for future studies of this genus.