2.1 Sample sites and materials
The sample sites are located at the Hualongshan Mountains National
Nature Reserve in Shaanxi Province, with the geographic coordinates
109°16′41″ - 109°30′29″ E, 31°54′39″ - 32°08′13″ N. The highest peak of
the Hualongshan Mountains is 2917 m above sea level, which is the second
highest peak of the Dabashan Mountains in China. Based on the vegetation
regionalization of China, the Hualongshan Mountains belong to the
subtropical evergreen broadleaved forest, north subtropical evergreen
forest, and deciduous broadleaved mixed forest areas.
In the Hualongshan Mountains, the diploid grows within the long and
narrow areas on the shady slopes of gullies, from west to east, whereas
the tetraploid grows under the arbor forests at 40° areas of the
northern slopes. Ten 1 m × 1 m plots were set in the diploid and
tetraploid sample areas, respectively. Within ten samples, a total of 93
and 107 diploid and tetraploid individuals were collected from all the
visible individuals in the sample areas. And, the specific spatial
positions of each sampled individual of the two ploidies were marked and
recorded.