As one of the biodiversity centers of wild Rosa, China is home to 95 species (65 endemic) of Rosa, accounting for nearly half of the world total (Ku and Kenneth, 2003). The Xinjiang Uygur Autonomous Region is a large and sparsely populated area located in the northwest of China covering 1.6 million km2 (about one-sixth of the total land area of China). Separated by the Tianshan Mountains, north Xinjiang is characterized by temperate climate, whereas south Xinjiang possesses a warm temperate climate. These complex environments make Xinjiang host to a rich variety of plant species. Although officially 14 species (including three botanical varieties) of wild Rosa are found in this region (Ku and Kenneth, 2003), there may be as many as 22 wild Rosa species in the region (Bao, 1993; Liu, 1993; Liu and Cong, 2000; Ma and Chen, 1990).
Shrubs 1–2 m tall. Branchlets terete, straight or slightly curved, glabrous; prickles in pairs below leaves or scattered. Leaves including petiole 4.5–10 cm; leaflets 7–9, elliptic, oblong, or ovate, rarely obovate, 1.5–4 cm long, 1–3 cm wide, glabrous or pubescent. Flowers often 3–6 in corymb, sometimes solitary, 1.5–3 cm in diam.; pedicel 1–1.8 (–3) cm, glandular; bracts ovate, pubescent, glandular hispid, apex acuminate. Sepals 5, ovate-lanceolate, leaflike, abaxially sparsely pubescent and glandular hispid, adaxially densely pubescent, margin entire. Petals 5, white or pink, obovate, apex erose. Hip red, oblong or ovoid, 1–1.8 cm in diameter, glabrous, often shiny, apex with a short neck and persistent, erect sepals.
Other recorded botanical varieties of R. laxa include 1) var. mollis, 2) var. kaschgarica, and 3) var. tomurensis. Rosa laxa varies considerably in terms of morphological characteristics. There is abundant inter- and intrapopulation genetic diversity among six natural populations of R. laxa var. laxa in the Tianshan Mountains of north Xinjiang (Guo, 2010). However, there is little information in the literature focused on the detailed descriptions (and specimens) of these botanical varieties in the Xinjiang region. Furthermore, only a relatively small area has been previously surveyed for R. laxa, although it is well known that Xinjiang is a biodiversity center of Rosa.
In this study, we reported the results of a recent survey (2007–18) of the distribution of R. laxa botanical varieties and their morphological characteristics in the Xinjiang region. In addition to the usual morphological characters, we also measured pollen traits. Because the morphological characteristics of pollen grains are generally unaffected by environmental factors but exhibit strong genetic stability, considerable evolutionary information regarding species and botanical varieties may be inferred from pollen characteristics (Wang and Wang, 1983; Wrońska-Pilarek and Jagodziński, 2011).
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