Patterns of chloroplast DNA variation in Cycas debaoensis (Cycadaceae): conservation implications

Abstract

Climate changes during glacial periods have had significant effects on the current distribution of plant species. Palaeontologial data suggest that modern cycads originated in southwest China. Cycas debaoensis (Cycadaceae) is an endangered species restricted to a small area of southwest China. This species has been classified into two types: sand and karst, according to the soil matrix they grow on. To determine the locations of its glacial refugia and its genetic structure, we examined chloroplast sequence variation of the atpB-rbcL and psbA-trnH intergenic spacers. Four chloroplast DNA haplotypes were obtained from 120 individuals collected from 11 populations covering the entire extant distribution range of the species. Significant population subdivision was detected (G ST = 0.684 and F ST = 0.74160), suggesting low levels of gene flow between regions and populations. There was marked haplotype differentiation between populations in the sand and karst regions, with only one haplotype being present in both. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest that C. debaoensis experienced range contraction during glacial periods, and that the current populations are still confined to the areas of the original refugia. These results implied that isolated refugia might have maintained in both sand and karst regions during the last glacial maximum and even earlier glaciations. The low within-population diversity of C. debaoensis suggested that there were strong bottleneck events or founder effects within each separate region during the Quaternary climatic oscillations. These findings are important for the conservation of this endangered species.

Middle-Upper Pleistocene climate changes shaped the divergence and demography of Cycas guizhouensis (Cycadaceae): Evidence from DNA sequences and microsatellite markers

“…Thus, we can compare the genetic diversity of C. guizhouensis with other Asian Cycas species using the similar molecular markers. Cycas guizhouensis had higher genetic diversity (Tables 2, S2 and S3) than C. debaoensis 27, but had slightly lower genetic diversity than C. simplicipnna 9 and C. multipinnata 10. cpDNA-based studies on 170 plant species revealed a mean value of H T  = 0.6747, while H T estimated from C. guizhouensis by four cpDNA was 0.841 which implied that C. guizhouensis had a high level of genetic diversity.…”

“…Distinct demographics were detected in different plant taxa as a result of glacial and interglacial periods. Gymnosperm species, such as Taxus wallichiana 53, Cycas revoluta , and Cycas taitungensis 54, have experienced population expansions during the most recent glacial period, while Cycas debaoensis 27, Cycas simplicipinna 9 and Cycas multipinnata 10 have experienced population contractions. In this study, four cpDNA, three nuclear genes and 13 microsatellites generated inconsistent results for the demography of C. guizhouensis .…”

“…Protection measures can be proposed by relying on detailed population genetic studies. Several population genetic studies on cycads based on different molecular markers have been recently published91011192728. These publications provide references for the study of other cycad species.…”

Morphometric and geographical variation in theCeratozamia mexicanaBrongn. (Zamiaceae) complex: evolutionary and taxonomic implications

“…Either through the lens of 'classical' population genetics (Gonz alez-Astorga et al, 2003b, 2005, 2006 or through phylogeography (Huang et al, 2001;Chiang et al, 2009;Kyoda & Setoguchi, 2010;Zhan et al, 2011;Guti errez-Ortega, Kajita & Molinar-Freaner, 2014;Nolasco-Soto et al, 2015), the results of further work in this direction will allow the construction of ancestor-descendant hypotheses involving known populations, as well as the assessment of demographic history and genetic differentiation between these populations. In accordance with our population-genetic research programme, evolutionary inferences derived from these phylogeographical interventions will constitute the starting point in species recognition and circumscription.…”

Demografía histórica de Anadenanthera colubrina var. cebil (Leguminosae) en Argentina.

“…2 a y c). Debido a la organización estructural conservada del ADNcp en plantas superiores, sumado al reducido flujo génico mediado por semillas, pueden esperarse niveles reducidos de diversidad genética en este genoma (Zhan et al, 2011).…”