4.2 | Influence of topographic feathers on genetic structure
Topographic features often act as a physical barrier to gene exchange between populations of species (Pilot et al., 2006). A previous study of giant pandas has shown that natural barriers might have decreased gene flow between the Xiaoxiangling and Daxiangling regions (Zhu, Zhan, Meng, Zhang, & Wei, 2010). Moreover, using landscape genetic approaches, researchers investigated the population genetics of American mink, and found the Cairngorms Mountains may act as a major geographical barrier to gene flow among populations (Zalewski, Piertney, Zalewska, & Lambin, 2009). A study by Wei et al. (2013) also showed that gene flow ofEuptelea pleiospermum was limited by mountain ridges.
As mentioned before, Orchidaceae is often characterized by relatively low levels of genetic differentiation among populations because of long-distance dispersal afforded by minute size of seeds, and geographical features usually have no impacts on their spatial genetic structure. For example, Perez-Escobar et al. (2017) noted that the Andes seem not to have been much of a barrier to the dispersal of lowland epiphytic orchids. Consistent with the previous result, we also found the Qinling Mountains do not appear to be a geographic barrier of genetic exchange for terrestrial orchid C. faberi . However, another study of an epiphytic orchid found that seed flow among twelve populations in Costa Rican mountain ranges was comparatively limited (cpDNA, FST = 0.443), which possibly due to the directional prevailing winds (Kartzinel, Shefferson, & Trapnell, 2013).