Allozyme and DNA sequence comparisons of nine species of Encephalartos (Zamiaceae)

Phylogenetic relationships between Encephalartos altensteinii Lehmann, E. a renarius R.A. Dyer, E. horridus (Jacquin) Lehmann, E. latifrons Lehmann, E. lehmannii Lehmann, E. longifolius (Jacquin) Lehmann, E. princeps R.A. Dyer and E. trispinosus (Hooker) R.A. Dyer were studied, using E. ferox Bertolo ni f. as outgroup. Three continuous and one discontinuous buffer systems we re used and gene products of 14 enzyme coding loci were examined by horizon tal starch gel-electrophoresis, Genetic variation was studied in a cultivat ed population of E. lehmannii and the average heterozygosity value for this population is 13.5%, which falls within the range reported for other cycad species. Fixed allele differences between the species studied was not foun d at any of the loci studied, which suggest that these species are closely related. DNA sequence analysis of rbcL and ITS 1 & 2 genes (1428 and 895 ba sepairs, respectively) confirmed the close genetic relationships between th ese taxa. According to ITS and rbcL sequences E. altensteinii and E. prince ps are sibling taxa which form a sister group to E. arenarius, E. horridus, E. latifrons, E. lehmannii, E. longifolius, and E. trispinosus. The geneti c distances between both groups were 0.12-0.47% for ITS and 0.080.16% for r bcL DNA. The results indicate recent (probably pleistocenic) speciation for this group of cycads, and the relationships are discussed with reference t o affinities based on morphology and distribution. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.