Assessment of the genetic diversity of the critically endangered aloe peglerae Schonland (Asphodelaceae) by means of inter-simple sequence repeat (ISSR) markers

Abstract

Aloe peglerae Schönland, commonly known as the Red-hot Poker Aloe or Magaliesberg Aloe, is listed as Critically Endangered on the Red List of endangered plant species of South Africa. It is a slow growing succulent, endemic to the Magaliesberg, with a disjunct population near Krugersdorp, within the Gauteng and North West provinces of South Africa. Sharp population declines due to poaching and habitat loss have prompted both reintroduction programmes and associated studies on the genetic variability of the species across its distribution range, all in an attempt to better inform future conservation efforts. This study sampled 12 A. peglerae localities from which the genetic diversity was assessed using Inter Simple Sequence Repeat (ISSR) DNA “fingerprinting”, coupled with automated fragment detection. Three fluorescently labelled ISSR primers were used to amplify ISSR profiles from the 174 samples obtained from the 12 localities. Following rigorous data quality assessment, a final data set of 145 samples was obtained. The use of automated detection of ISSR fragments was extremely sensitive and the data set comprised over 2500 bands obtained from just three primers. Analysis of genetic variation was conducted using four different methods: STRUCTURE analysis, Networks, Phenetic analyses (using both UPGMA and Neighbour Joining (NJ)), and AMOVA. Results from these analyses indicate a gradual genetic transition between eastern and western localities along the Magaliesberg mountain range, representing one large population, as well as a completely distinct population from the Krugersdorp area. While samples from different localities usually possess enough differentiation to be generally identified as separate groups, those in close geographical proximity share sufficient similarities to suggest that conservation translocations can utilise propagules from neighbouring localities to augment and/or reintroduce depleted populations. Both in-situ and ex-situ conservation of the Krugersdorp population is urgently required, and translocations into this habitat should be done using propagules from within this population alone. This study highlights the advantages of using automated detection of ISSR fragments to provide many more data points than conventional agarose gel visualisation. As such, this approach is cost-effective and is recommended for studies assessing the genetic diversity of rare and endangered plant taxa.