Genetic Variation in the Qinghai-Tibetan Plateau Endemic and Endangered Conifer Cupressus gigantea, Detected Using RAPD and ISSR Markers

Abstract

Assessing the level and distribution of genetic diversity of rare tree species is essential for their management and the development of effective conservation strategies. Cupressus gigantea is a long-lived endemic cypress of the west Qinghai-Tibetan Plateau and the tallest tree in its genus. The current populations of this species are fragmented and highly disturbed. We used RAPD (Random Amplified Polymorphic DNA) and ISSR (Inter-Simple Sequence Repeat amplification) markers to assess the genetic variation and population structure of this endangered cypress. The 15 RAPD primers used in this study amplified 108 reproducible bands, 49 (45.4%) of which were polymorphic, while the 12 ISSR primers amplified 94 bands, 65 (69.2%) of which were polymorphic. Analysis of Molecular Variance (AMOVA) indicated that 49.7% and 38.3% of the variation was attributable to differences between populations for the RAPD and ISSR markers, respectively; relatively high compared to values reported for other conifer species. These estimates were also similar to Gst values obtained from Nei’s gene diversity analyses (RAPD = 0.41 and ISSR = 0.36), and suggest that there is a high degree of population differentiation in this narrowly-distributed conifer. The genetic structure of this species has probably been shaped by its long life cycle and climatic changes during the Quaternary. The high degree of population differentiation in this species highlights the need for additional conservation measures, including measures to protect of all of the remaining populations. The substantial similarities between the results of the RAPD and ISSR analyses of samples from the same individuals indicate that they can be interpreted with high levels of confidence.

Assessment of genetic diversity and population structure of an endemic Moroccan tree (Argania spinosa L.) based in IRAP and ISSR markers and implications for conservation

“…Similar results were found by Mouhaddab et al (2015) using ISSR markers and by Pakhrou et al (2016) using AFLP markers. The high differentiation among A. spinosa L. populations is consistent with studies of other endemic species like Cupressus gigantean (Gst = 0.36) (Xia et al 2008) while it was higher than other forest species such as sessile oak (Gst = 0.026) (Kremer et al 2002). Moreover, the high genetic differentiation and gene exchange between studied populations are expected for several reasons.…”

Genetic variation of isolated Picea balfouriana populations from the southeast of the Qinghai-Tibet Plateau

“…Compared with previous studies, the amount of genetic differentiation of P. balfouriana was lower than that of P. asperata, which is distributed narrowly and discontinuously , but distinctly higher than the values detected among populations of widespread Norway spruce (Maghuly et al, 2006;Meloni et al, 2007), transcontinentally distributed black spruce (Perry and Bousquet, 2001) and both disjointedly and continuously distributed Sitka spruce (Gapare et al, 2005). Moreover, high levels of population differentiation have been commonly observed in plant species from the southeast of the Qinghai-Tibet Plateau when compared with other species belonging to the same genus, e.g., Cupressus gigantean (Xia et al, 2008), P. asperata , Gentiana atuntsiensis and G. striolata (Zhang et al, 2007), Megacodon stylophorus (Ge et al, 2005) and Populus cathayana (Lu et al, 2006;Peng et al, 2005). Habitat fragmentation in the southeast of the QinghaiTibet Plateau may account for the relatively high levels of F ST values.…”

Genetic Diversity of the Critically Endangered Thuja sutchuenensis Revealed by ISSR Markers and the Implications for Conservation

“…The ISSR analysis conducted for the T. sutchuenensis populations located in North-East Chongqing, China, revealed the presence of an appreciable level of genetic diversity, which was more than that of its relatives Calocedrus macrolepis [20], Taiwania cryptomerioides [21], Cupressus gigantea [22] and C. chengiana [23]. This is an expected result for a woody, moderately long-lived, outcrossing and wind-pollinated species [24].…”