INTERFAMILIAL RELATIONSHIPS IN MYRTALES - MOLECULAR PHYLOGENY AND PATTERNS OF MORPHOLOGICAL EVOLUTION

Numerous phenotypic (morphological, palynological, cytological, and an atomical) studies have been conducted on Myrtales, yet the detailed re lationships among the families of the order remain elusive. In this pa per, the rbcL sequences of 50 taxa (39 representatives of Myrtales and 11 rosid outgroups) were analyzed using parsimony and maximum likelih ood to provide a phylogenetic hypothesis of intraordinal relationships in Myrtales. The congruence between the phenotypic data from an earli er study and the rbcL topology was assessed to identify the potential synapomorphies that would corroborate the clades supported by the mole cular tree. The rbcL consensus tree defined two major clades in the or der. The first clade comprised a Myrtaceae lineage sister to a Melasto mataceae Lineage and the second clade included Onagraceae, a Lythracea e lineage, and Combretaceae. Phenotypic characters suggest that the an cestor of the first clade was characterized by the acquisition of fibr ous seed exotegmen, while the ancestor oi the second clade had flowers with stamens inserted directly on the rim of the hypanthium. However, branch support for the basal split of Myrtales is weak, possibly as a result of rapid early radiation in the order.