Abstract:

Aim: This study aims to clarify the species diversity, distribution patterns, and environmental adaptation mechanisms of the genus Calligonum, in order to provide a scientific basis for its taxonomic revision. 

Methods: Global taxonomic data and multi-source databases including Global Biodiversity Information Facility (GBIF) were integrated to clarify its global distribution pattern; morphological measurements and comparative analyses of achenes from Central Asian specimens in the Tashkent Plant Herbarium (TASH) collection were conducted; a systematic investigation of its phylogenetic relationships, chromosomal variations, and ecological adaptation mechanisms was carried out through a multidisciplinary literature review. 

Results: Calligonum was widely distributed across arid regions from the Sahara to Central Asia, with Central Asia serving as its distribution and diversity center (34 recorded species). As the eastern margin of its distribution, China hosted 23 species, 17 of which were shared with Central Asia. This disjunct circum-Mediterranean distribution pattern may be associated with geological events such as the uplift of the Himalayas. The distribution of Calligonum was co-influenced by moisture, temperature, and soil factors. It was primarily found in arid zones with annual precipitation below 200 mm, exhibiting significant interspecific divergence in water-use strategies. Low temperatures and seasonal variations restricted its northward expansion, and it showed a preference for low-salinity, highly alkaline, and sandy soil types. The genus employed multi-level adaptive strategies, including physiological regulation and stoichiometric adjustments, to cope with arid conditions, thereby demonstrating clear ecological niche differentiation. 

Conclusion: As a keystone taxon in the arid regions of Central Asia, Calligonum exhibits rich species diversity and rapid evolutionary potential. Future studies should integrate multidisciplinary approaches such as genomics and ecology to enhance understanding of its speciation and adaptation mechanisms. Furthermore, comprehensive conservation strategies focusing on germplasm preservation and ecological restoration should be promoted to ensure the long-term sustainability of the genus and its ecological functions.

Key words: Central Asian desert region, Calligonum, distribution center, species diversity