Genetic diversity within and among populations of Neopicrorhiza scrophulariiflora (Scrophulariaceae) in China, an endangered medicinal plant

Abstract

Neopicrorhiza scrophulariiflora Pennel (Hong) (Scrophulariaceae) is an endangered medicinal plant, endemic to the Eastern Himalayas and the Hengduan Mountains. Levels of genetic variation and genetic structure of seven populations of N. scrophulariiflora in China were studied using inter-simple sequence repeat (ISSR) markers. Thirteen primers amplified 82 total loci from 7 populations composed of 136 individuals. All 82 loci were polymorphic, showing a percentage of polymorphic bands (PPB) of 100%, indicating considerable genetic variation at the species level. In contrast, a low level of genetic diversity within populations was detected with a mean PPB of 30.56%. In addition, Nei’s genetic diversity analysis (0.4073) and Shannon’s diversity index (0.5917) revealed similar genetic structure. High levels of genetic differentiation (Gst = 0.6955) and restricted gene flow (Nm = 0.2198) among populations were also detected. Anthropologic impacts, together with clonal propagation, genetic drift and geographical isolation might be the reasons which had shaped the genetic structure of this species.

Introduction

Neopicrorhiza scrophulariiflora Pennel (Hong) (Scrophulariaceae), a monotypic genus perennial species, is endemic to the Eastern Himalayas and Hengduan Mountains (Wu et al., 2003). It is a typical alpine plant, with a distribution ranging from 3600 m to 4200 m in elevation (Zhong and Yang, 1979).

The long, creeping and highly bitter rhizomes (Rhizoma Neopicrorhizae) named Huhuanglian are of high medicinal value, and have been officially listed in the Pharmacopoeia of the People’s Republic of China for the treatment of fever, jaundice, hemorrhoids, and dysentery by Traditional Chinese and Tibetan Medicine (Chinese Pharmacopoeia Commission, 2005). Because of the impact of global warming and anthropogenic activity, natural populations of this species have suffered rapid declines. It is now classified as an endangered species in the Chinese Plant Red Book (Fu, 1992) and is listed among the second-category of key protected wild plants in China.

Understanding genetic variation within and among populations is essential for the establishment of effective conservation practices for rare and endangered plants. However, nothing is known about the population genetics of this species.

Several neutral molecular makers including ISSR (inter-simple sequence repeats) (Zietkiewicz et al., 1994) were proved to be effective tools for detection of genetic diversity and genetic structure, especially in the case of endangered species such as Changium smyrnioides (Qiu et al., 2004), Sinojackia dolichocarpa (Cao et al., 2006), Primula merrilliana (Shao et al., 2009) and Sonneratia paracaseolaris (Li and Chen, 2009).

In the present study, we investigated genetic diversity and population structure among seven populations representing the entire distribution range of N. scrophulariiflora using the ISSR technique. The main objectives of our study were (1) to reveal the amount of genetic diversity and how the genetic variation was distributed within and among the populations; (2) to detect whether there was correlation between genetic distance and geographical distance; and (3) to suggest methods for effective future conservation of this endangered medicinal species.