1 | INTRODUCTION
The Qinling Mountains are a natural boundary between China’s north and
south stretching over 1,600 kilometers in east-west direction, which
formed approximately during the Mesozoic and Cenozoic (Zhang, Cawood,
Dong, & Wang, 2019). Due to most of the mountains are higher than 2000
meters and diversified topography, the mountains form an important
boundary and are home to a diverse variety of wildlife, many of which
are rare on earth. Recent phylogeographic and population genetic studies
have showed that the Qinling Mountains probably served as a barrier for
wild plants and animals, such as Paeonia (Yuan, Cheng, & Zhou,
2012; Xu et al., 2019), Sinopodophyllum hexandrum (Liu, Yin, Liu,
& Li, 2014), Actinidia chinensis (Wang, Liao, & Li, 2018), and
reptile (Yan, Wang, Chang, Ji, & Zhou, 2010; Huang et al., 2017).
However, contrary to these studies, some other results suggested that
the Qinling Mountains have no obvious impact on genetic structure (Zhan,
Li, & Fu, 2009). This discrepancy may depend on the mechanisms by which
the species survive and disperse, as well as how they respond to the
surrounding environment.
Over the past few decades, habitat fragmentation occurred in the Qinling
Mountains due to human’s large-scale forest logging, building of roads
and urbanization. The habitat fragmentation has resulted in low genetic
diversity and population structure not only for plants but also for
other species, including golden snub-nosed monkey and giant panda (Huang
et al., 2016; Ma et al., 2018). For most plants, habitat fragmentation
often reduces gene flow and genetic diversity by disrupting the movement
of seed (Sebbenn et al., 2011; Lander, Harris, Cremona, & Boshier,
2019; Ony et al., 2020). It was reported that seed dispersal play
important roles in determining genetic variation patterns in fragmented
landscapes (Browne & Karubian, 2018).
Cymbidium faberi is a terrestrial orchid enlisted in Appendix of
the Convention on International Trade in Endangered Species of Wild
Fauna and Flora (CITES). It is a species with a distribution from Nepal,
Northeast India to south of China, north to the Qinling Mountains (Flora
of China Editorial Committee, 2009). It grows on rocky and scrubby
slopes, usually in Quercus variabilis forests at altitudes of 700
– 3000 m. Like many other cymbidium species, C. faberi is
a self-compatible allogamous species that depends on insect pollinators
such as honeybees for seed production (Suetsugu, 2015). The dust-like
seeds are often produced in huge numbers, and they usually lack
endosperm and the embryo is undifferentiated. The empty space inside
seeds and the trichomes on the endocarp make them well suited for wind
dispersal (Arditti & Ghani, 2000; Gamarra, Ortúñez, Cela, & Merencio,
2018). Thus, topographic feathers such as the Andes seem not to have
been much of a barrier to the dispersal of lowland epiphytic orchidsCycnoches (Perez-Escobar et al., 2017). However, a recent study
of an epiphytic orchid found a seed dispersal barrier between
northwestern and southeastern populations within Costa Rica (Trapnell et
al., 2019).
To date, whether geological barriers such as the Qinling Mountains and
habitat fragmentation in the areas have an impact on C. faberiremains unknown. Here, we analyzed 271 samples based on maternally
inherited two chloroplast DNA sequences to evaluate the impact of
Qinling Mountains and habitat fragmentation on genetic structure ofC. faberi . The aims of this paper are: (1) to assess the level of
genetic variation and spatial genetic structure of C. faberi in
the Qinling Mountains; (2) to explore the demographic history ofC. faberi in the Qinling Mountains; and (3) to try to explain the
genetic structure based on species seeds dispersal ability and human
activity that have influenced it.