THE GENETICS OF PTYCHOSPERMA-BLEESERI, A RARE PALM FROM THE NORTHERN-TERRITORY, AUSTRALIA

Ptychosperma bleeseri is known from only eight small monsoon rainfores t patches located in the vicinity of Darwin, Australia. One population consists of only one adult plant and only one patch contains a popula tion of more than 50 adult plants. A survey of the genetic diversity w ithin the species was undertaken using isozyme analysis. Almost no gen etic variation was recorded. Of the 223 wild collected samples tested, only four individuals varied at a single locus out of the 10 loci ana lyzed. The lack of diversity among populations suggests that the exist ing populations are derived from a common, genetically depauperate, so urce which has acted as a founder population. P. bleeseri was compared with the other Ptychosperma species which occur naturally in Australi a (P, macarthurii and P. elegans). Each of these species; was found to differ consistently at several enzyme loci thus indicating that P. bl eeseri does not simply represent an outlying population of either of t hese two species. Cultivated specimens of P. bleeseri were shown to ha ve hybridized with other cultivated Ptychosperma species when grown to gether. This presents a problem for ex-situ conservation. Since palms are particularly favoured by Darwin residents in their gardens and pub lic places, the location of urban development in close proximity to wi ld populations of P. bleeseri has the potential to introduce other Pty chosperma species into the wild populations. This could have serious e ffects on the genetic integrity of the species. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.