Population genetic structure of Tunisian Hypericum humifusum assessed by RAPD markers

Abstract

The genetic variation within and among seven Tunisian natural Hypericum humifusum L. populations belonging to three bioclimatic zones (sub-humid, upper semi-arid, and lower semi-arid) was assessed using random amplified polymorphic DNA markers. Eight selected primers produced a total of 166 bands, of which 153 were polymorphic. The genetic diversity within a population, based on Shannon's index and percentage of polymorphic loci, was relatively high. The level of variation among populations did not differ significantly. However, the variation among populations grouped according to their bioclimates was significant. A high differentiation and a low gene flow were observed at all spatial scales among all populations. The upper semiarid populations exhibited the highest differentiation. The relationship between genetic and geographic distances was not significant indicating that structuring occurred due to founding events. The UPGMA analysis based on Nei & Li's coefficients showed that individuals from each population clustered together. The cluster analysis based on genetic distances among populations did not show clear groupings relevant to geographical distances or bioclimates. The high differentiation among populations even through a small geographic range implies the collection of seeds from all populations to preserve, ex-situ, extant variation in the species. Populations from the upper semi-arid zone showing the highest genetic diversity should be first prospected.

Genetic diversity assessed by microsatellite markers in the amphicarpic species Trifolium polymorphum Poir.

“…However, the loss of large areas of these grasslands in Rio Grande do Sul due to conversion to annual agricultural crops, especially soybean and corn and silviculture (mainly of eucalyptus and pine), and the degradation associated with the invasion of exotic species such as Eragrostis plana Ness (called capim anoni in Brazil) is a major threat to the genetic diversity of this highly biodiverse natural ecosystem that provides soil carbon storage, erosion control, soil water infiltration, pollinator availability and forage production (Pillar et al 2012). Therefore, conservation strategies to understand patterns of genetic variation within and between populations are crucial to assess the current status of populations (Béjaoui et al 2011, Corlett 2016 and to establish a collection strategy for the conservation and use of germplasm Hodgkin 2002, Whitlock et al 2016).…”