VARIATION WITHIN AND AMONG THE CHLOROPLAST GENOMES OF MELALEUCA-ALTERNIFOLIA AND MELALEUCA-LINARIIFOLIA (MYRTACEAE)

Melaleuca alternifolia and M. linariifolia are commercially important Australian species harvested for their essential oils. Both species ha ve relatively narrow and disjunct distributions on the central coast o f eastern Australia. Variation in the chloroplast genome was assessed for eight individuals from each of twelve populations, representing th e species' geographic range. Low nucleotide diversity within M. altern ifolia contrasted with high nucleotide diversity in M. linariifolia. C pDNA data are consistent with the southern population of M. alternifol ia being a hybrid population with M. linariifolia. The two species are sympatric in this region. Variation in M. linariifolia was geographic ally structured, with northern populations differing from southern pop ulations by seven restriction site mutations, five length mutations an d an inversion. There was no evidence of hybridisation of the cp genom e of northern M. linariifolia with the partially sympatric species M. trichostachya, Intra- and interspecific variation in the chloroplast g enomes of M. alternifolia, M. linariifolia, and M. trichostachya indic ate considerable potential for the use of intraspecific cpDNA studies in examining phylogenetic relationships in melaleucas.