TheUlmaceae, one family or two? Evidence from chloroplast DNA restriction site mapping

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The Ulmaceae is usually split into two subgroups, referred to as either tribes or more commonly subfamilies (Ulmoideae andCeltidoideae). The two groups are separated, with some exceptions, on the basis of leaf venation, fruit type, seed morphology, wood anatomy, palynology, chemistry, and chromosome number. Propositions to separate the two groups as distinct families have never gained general acceptance. Recent morphological and anatomical data have suggested, however, that not only is family status warranted but thatCeltidaceae are more closely related toMoraceae and otherUrticales than toUlmaceae. In order to test these alternative sets of relationships, restriction site mapping of the entire cpDNA was done with nine rare cutting enzymes using 11 genera ofUlmaceae s. l., three other families of theUrticales, and an outgroup family from theHamamelidae. Cladistic analysis of the data indicates thatUlmaceae s. l. is not monophyletic and that distinct families (Ulmaceae andCeltidaceae) are warranted; thatUlmaceae is the sister group toCeltidaceae plus all other families in the order; and thatCannabaceae might be nested withinCeltidaceae. Familial placements of various problematic genera (e.g.Ampelocera, Aphananthe) are resolved and character evolution of key morphological, anatomical, chemical, and chromosomal features are discussed.