A re-examination of the s (Amaranthaceae) of Saudi Arabia and their polymorphs.

During the period from 1964 to 1999 Saudi Arabian species of were wrongly treated under the European species, L. Recent explorations proved that there are two separate allopatric species of in Saudi Arabia, one inhabiting the inland salt-marshes of the Najd (highlands) and the other inhabiting the Arabian Gulf Coast (lowlands). Morphological, ecological and exploratory studies confirm that they are two distinct species. The two species differ in features of bark, axillary spikes, basal vegetative segment(s) of spike, fertile segments, colour of senescent plants, and flowering, fruiting and germination phenology. As both the species have been described earlier from Iran, they are now new records for Saudi Arabia. The species are, ssp. (Akhani) Kadereit & Piirainen and Akhani. , of which the status was thought doubtful has been confirmed. Both the species have been described and illustrated. Each species comprises a number of polymorphs. As leaves and flowers are rudimentary, confusing species circumscriptions, a proliferation of binomials has resulted in the taxonomy of . To mitigate such confusion, the full range of variability of the Saudi Arabian species has been documented.