Figure 7.

Proposed historical patterns of the migration and recolonization of Nitraria tangutorum in arid northwest China. (A) ~2.53 Ma: intraspecific differentiation occurred within the eastern groups of N. tangutorum triggered by the initial strengthening of the East Asian winter monsoon (EAWM). (B) ~1.82–0.62 Ma: putative routes of migration and recolonization of N. tangutorum across the Hexi corridor supported by the climatic conditions established by the EAWM. Color coding is consistent with Figure 2: brown spots represent the ancestor of N. tangutorum; purple, green and orange spots represent the haplotypes from the East-A, East-B, and West lineages, respectively. Red arrows represent the putative dispersal routes of N. tangutorum. Black arrows and number of arrows represent the direction and intensity of the EAWM and East Asian summer monsoon (EASM), respectively.