Biogeography and systematics of Ourisia (Plantaginaceae)

Date
2004-05
Authors
Meudt, Heidi Marie, 1974-
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Abstract

This dissertation examines the biogeography, taxonomy, species relationships, and morphological evolution of the genus Ourisia (Plantaginaceae; Scrophulariaceae s.l.). Ourisia is distributed in subalpine to alpine habitats of South America, New Zealand, and Tasmania. This classic austral biogeographic pattern displayed by numerous extant plants and animals has been attributed to either Gondwanan vicariance or long-distance dispersal. To test these hypotheses for Ourisia, a molecular phylogenetic approach was used to reconstruct the evolutionary history of most species of Ourisia based on two chloroplast and two nuclear DNA markers using parsimony and Bayesian methods. Parametric bootstrapping rejected both the Gondwana biogeographic hypothesis and an Australasian origin for the genus. Instead, Ourisia likely arose in the southern Andes, and subsequently spread to the north-central Andes and to New Zealand and Tasmania via long-distance dispersal. These results corroborate other recent molecular phylogenetic studies that have highlighted the important role of dispersal in the evolutionary history of many other high-elevation plants in the Southern Hemisphere. The molecular phylogeny also elucidated interesting biogeographic trends within both South America and New Zealand, which are discussed in light of the geological history of each region. A detailed morphological study of herbarium specimens resulted in the first comprehensive monograph of Ourisia. Twenty-seven total species were recognized from South America (15), Tasmania (1), and New Zealand (11). A new infrageneric classification for Ourisia was proposed based on habit. The three suffruticose southern Andean species comprise subg. Suffruticosa, while the remaining 24 herbaceous species make up subg. Ourisia. This infrageneric classification contrasts with that of Poeppig and Endlicher, who delimited the two subgenera within Ourisia based largely on calyx symmetry. Separate and combined phylogenetic analyses of 21 morphological characters in addition to the molecular data for 29 of the 33 species and varieties of Ourisia plus the outgroup supported the monophyly and sister relationship of the herbaceous and suffruticose subgenera. Six other morphological characters, including leaf attachment, presence of an inflated hypogynous disc, seed type, ovary vestiture, (internal) calyx vestiture, and inflorescence structure, also support this circumscription. Evolution of these and other characters, in addition to species relationships, were also addressed.

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