4. Discussion
4.1Genetic diversity of P. villosa
Genetic diversity refers to intraspecific genetic variation and is closely linked to the evolutionary potential of a species to adapt to adverse environments (Ma & Qian, 1994). The study of genetic diversity can facilitate understanding of spatial genetic patterns of a species, and elucidate its evolutionary processes and adaptive mechanisms (Hao, 2005). In the present study, we observed high genetic diversity at species-level in P. villosa (P =95.72%, I = 0.3316) and the population-level (P= 32.02%, I = 0.1640) (Table 2 & Table S1). Compared to genetic diversity in other species of Poaceae assessed using AFLPs, genetic diversity in P. villosa was slightly lower than that ofChascolytrum bulbosum (P = 98.2%, h = 0.1500; Silva, Essi, Welker, & de, Souza-Chies, 2016), and was higher than that of Leymus chinensis (P = 16.53%, I = 0.0890),Leymus racemosus (P = 16.53%, I = 0.0890), andDactylis glomerata (P = 61.70%, I = 0.2664) (Gong et al., 2007; Cai, 2016; Zhang, He, Zhao, Zhang, & Xu, 2017).
The underlying drivers of genetic diversity within species are generally a combination of biological properties, such as dispersal abilities and life history, and environmental factors, such as climate and anthropogenic activities (Loveless & Hamrick, 1984; Hamrick & Godt, 1996; Wang & Hu, 1996; Wen, Han, & Wu, 2010). The life history ofP. villosa frequently involves clonal reproduction via its rhizomes under harsh environmental conditions, although the species reproduces sexually by seed following wind pollination (Wang, Ge, & Dong, 1999; Li & Ge, 2001). In comparison with L. chinensis ,L. racemosus , and D. glomerata , the relatively high genetic diversity of P. villosa might be explained by one or more of several factors. Among these, our study design comprised more populations, which might lead to greater accuracy. However, biological explanations are more likely and include possible higher clonal fitness due to P. villosa having extremely robust, hardy rhizomes; high rates of seed production; and seedling regeneration, while rare within any one growing season, occurring often over the long lifetime of the species (Eriksson & Bremer, 1993; Helena & Mikko, 1996; Shimizu et al., 1998).