Abstract
Urticaceae is a family with more than 2000 species, which contains remarkable morphological diversity. It has undergone many taxonomic reorganizations, and is currently the subject of further systematic studies. To gain more resolution in systematic studies and to better understand the general patterns of character evolution in Urticaceae, based on our previous phylogeny including 169 accessions comprising 122 species across 47 Urticaceae genera, we examined 19 diagnostic characters, and analysed these employing both maximum-parsimony and maximum-likelihood approaches. Our results revealed that 16 characters exhibited multiple state changes within the family, with ten exhibiting >eight changes and three exhibiting between 28 and 40. Morphological synapomorphies were identified for many clades, but the diagnostic value of these was often limited due to reversals within the clade and/or homoplasies elsewhere. Recognition of the four clades comprising the family at subfamily level can be supported by a small number carefully chosen defining traits for each. Several non-monophyletic genera appear to be defined only by characters that are plesiomorphic within their clades, and more detailed work would be valuable to find defining traits for monophyletic clades within these. Some character evolution may be attributed to adaptive evolution in Urticaceae due to shifts in habitat or vegetation type. This study demonstrated the value of using phylogeny to trace character evolution, and determine the relative importance of morphological traits for classification.
Highlights
Ancestral state reconstructions (ASR) is an increasingly popular method to map morphological or ecological traits onto a molecular phylogeny [1], which has provided plenty of novel evolutionary insights [2,3,4,5,6]
This study demonstrated the value of using phylogeny to trace character evolution, and determine the relative importance of morphological traits for classification
Molecular data confirms that the family is monophyletic if Cecropiaceae is included [20, 21], but within the family many relationships that had been presumed based on morphology were contradicted, indicating homoplasy in characters previously thought to be diagnostic at genus level and above
Summary
Ancestral state reconstructions (ASR) is an increasingly popular method to map morphological or ecological traits onto a molecular phylogeny [1], which has provided plenty of novel evolutionary insights [2,3,4,5,6]. Contains more than 2000 species encompassing a broad range of morphological diversity (Fig 1), which are distributed from tropical to temperate regions, with the largest concentration of genera and species located in tropical Asia [17,18,19] It is a taxonomically difficult group, partly because many of the diagnostic characters require a microscope for accurate determination. There has not yet been a study that examined macromorphology of Urticaceae in the context of relationships indicated by molecular data Characters such as habit, phyllotaxis, stipule position, stipule fusion, and pistillate perianth, have been used to divide the family into five tribes [17, 22, 33,34,35]. Stigma type is highly polymorphic within most of these tribes and was usually considered useful at the between-genus level [36], whereas external morphology of achene was usually recognized as being important at the infrageneric level within Urticaceae [27]
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