A recent study carried out on a desert shrub by scientists from the Chinese Academy of Sciences may provide some clues about the genetic variation pattern of species in the Quaternary ice age. 

Ephedra przewalskii is a drought-tolerant shrub with an extensive geographic range. It inhabits extremely dry semi-deserts, piedmont, and gravelly saline soil, and usually forms a large area within the plant community. It is usually taken as an indicator species in plant communities of the deserts in northwestern China. 

SU Zhihao and his colleagues sampled a total of 469 E. przewalskii individuals from 45 populations, trying to uncover the evolutionary history of plants in arid northwestern China. 

Ephedra przewalskii probably originated in the late Tertiary, and the long evolution process in northwestern China has evidently accumulated the degree of genetic diversity. E. przewalskii spread across almost the entire arid zone in northwestern China.  

“The habitats varied in geology and topography, might harbour locally adapted genetic variations of the species. All these might help account for the high level of genetic diversity observed in the species,” said SU. 

Their study showed that during the Last Glacial Maximum, the climate was cooler and drier than it currently is, and the hostile environment would be expected to force species to suitable habitats, shrinking the distribution to a smaller range. 

Scientists found several factors may have direct correlation with the high level of genetic variations among the E. przewalskii populations and geographic groups. Geographic barriers might have promoted the vicariant processes of species, and repeated founder effect further solidified and increased the heterogeneity between populations. 

Their study “Evolutionary History of a Desert Shrub Ephedra przewalskii (Ephedraceae): Allopatric Divergence and Range Shifts in Northwestern China” was published on the latest issue of PLOS ONE.