Phylogeny, Biogeography and Systematics of Loasaceae subfam. Loasoideae

Abstract

Loasaceae subfam. Loasoideae is a mostly South American group of angiosperms that reaches its highest diversity in the Andean mountain ranges but also extends into Central America, Africa and Oceania. Although some molecular studies dealing with the relationships of this clade have been published previously, none has provided satisfactorily resolved phylogenetic reconstructions for the whole subfamily, with several groups showing poorly supported relationships. At the same time no quantitative historical biogeography studies have been attempted for the entirety of the subfamily. The aims of this thesis include to clarify the phylogenetic relationships of the genera of Loasaceae subfam. Loasoideae, including extensive taxonomic sampling covering every major clade in the subfamily, with special emphasis on <i>Nasa </i> and the South Andean Loasas clade. Based on the phylogenetic results, to address the historical biogeography of Loasaceae subfam. Loasoideae, and to identify and solve the major discrepancies between the currently accepted taxonomy and the molecular phylogenetic results. Using plastid markers (<i>trn </i>L- <i>trn</i>F, <i>mat</i>K, <i>trn</i>S-<i>trn</i>G and <i>rps</i>16) and ITS, Bayesian inference and Maximum likelihood approaches were used to reconstruct the phylogeny of Loasaceae subfam. Loasoideae. Divergence times were estimated using an uncorrelated relaxed molecular clock approach and estimation of the ancestral ranges of the subfamily was attempted employing Dispersal-Extinction-Cladogenesis. To reconstruct the possible ancestral ecologies of <i>Nasa</i> Ancestral character estimation was employed. The results in this thesis show that that sects. <i>Angulatae</i> and <i>Gripidea</i> are more closely related to <i>Blumenbachia</i> than to <i>Caiophora</i>, that <i>Loasa</i> sers. <i>Volubiles </i>+<i>Acaules</i> and <i>L</i>. ser. <i>Pinnatae</i> are phylogentically closer to <i>Caiophora</i> and <i>Scyphanthus</i> than to <i>Loasa</i> that <i>L</i>. ser. <i>Malesherbioideae</i> is more closely related to <i>Presliophytum</i> than to <i>Loasa</i> and that <i>Chichicaste</i> is nested in <i>Aosa</i>. Four well supported clades of <i>Nasa</i> were retrieved. The majority of the species of each clade share similar morphologies, although not a single autoapomorphy would apply to all the species within a clade, with some subclades differing dramatically from their closest relatives. The geographical structure of the molecular data and discordance between morphology and phylogenetic position of some species, suggest reticulate evolution. The most relevant taxonomic outcomes from this research include the segregation of two new genera (<i>Grausa</i> and <i>Pinnasa</i>) from <i>Loasa</i> the synonymization of <i>Chichicaste</i> with <i>Aosa</i> and the respective revisions of deserticolous <i>Presliophytum</i> and <i>Kissenia</i> with detailed descriptions of the species as well as data on morphology, distribution and ecology are provided. Historical Biogeography research indicates that Loasoideae could have diverged from its sister group in the Late Cretaceous-early Paleocene (83–62 Ma). Most extant genera-level clades, diverged from their sister groups by the Eocene, preceding the Andean orogenic events. Divergence within extant lineages appears to have happened more or less parallel to Andean uplift pulses and most genus level clades have had limited dispersal beyond areas adjacent to their ancestral area. For <i>Nasa</i>, the divergence of the four main clades from each other took place between ca. 29-9 Ma. The Amotape-Huancabamba-Zone and Central Andes were retrieved as the most probable ancestral area for the genus. Dispersal into the Northern Andes was detected independently eight times. Estimations on <i>Nasa</i> ancestral ecology indicate that the whole genus and most of the major clades have been restricted to intermediate elevation, seasonally dry Andean scrub habitats during most of their early histories. Finally it was found that phylogenetic effect on the thigmonastic patterns of stamen movement in Loasoideae is minor compared to the effect of the main pollinator-guilds to which the taxa are adapted. Thigmonastic pollen presentation in Loasoideae could thus be another dimension in the complex plant-pollinator interactions in this clade.