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Authors: Hühn, Philipp
Advisor: Kadereit, Gudrun
Hörandl, Elvira
Title: Phylogenetics and evolution of the Australian camphorosmeae (Amaranthaceae)
Online publication date: 12-Sep-2023
Year of first publication: 2023
Language: english
Abstract: The Australian Camphorosmeae are the most species-rich tribe of Amaranthaceae Juss. sensu lato in Australia, with about 150 species in currently 12 described genera. Their closest relatives, the genus Grubovia with three described species, are distributed in Central Asia. This study re-examined hypotheses regarding phylogeny, taxonomy, trait evolution, as well as diversification, radiation and migration in the course of Australia's aridification since the Miocene. A total of 104 species representing all 12 recognized genera of the Australian Camphorosmeae were analyzed using a modified RADseq laboratory and data analysis approach with subsequent Maximum Likelihood phylogenetic inference and Bayesian inference of species divergence times. In total, 25 vegetative, reproductive and ecological characteristics were investigated for their systematic relevance. The phylogenetic results do not support the current taxonomy and confirm concerns regarding an artificial generic delimitation. The species-rich genera Sclerolaena and Maireana turned out polyphyletic. The included Maireana species formed several species-poor clades, while the majority of Sclerolaena species formed a species-rich clade. Species-poor genera were resolved within larger genera or formed clades with other small genera. The phylogenetic clades may be circumscribed using combinations of morphological traits. In particular, the features of the multifariously developed fruiting perianth showed systematic relevance. The phylogenetic results, mapping of ecological traits and the outcome of the divergence time estimation shed new light on biogeographical hypotheses. The Australian Camphorosmeae presumably arrived in Australia during the Middle to Late Miocene. Colonization was likely promoted by pre-adaptation to arid and saline conditions. A littoral connection may have taken place by species adapted to coastal conditions that migrated along declining palaeodrainage systems to hypersaline inland habitats. Two rapid radiations during the Late Miocene overlap in time. Major climatic and geological changes during this period may have promoted initial diversification. As aridity intensified, this group diversified further during the Pliocene. Riverine Desert and Desert Lake habitats may have been the main migration corridors. Migration may have been multidirectional from south-west Australia to north-west Australia with subsequent west to east migration across the continents interior and diversification into more diverse habitats. The multifariously developed diaspores relate to different dispersal syndromes. The wind-dispersed wing-like perianths of Maireana favor fast, non-directional dispersal over long distances, across Australia’s relatively flat interior. This likely promoted rapid colonization of vacant habitats during the Late Miocene and Pliocene. Increased mobility and consequent increased gene flow probably resulted in lower speciation rates, which is now apparent in the species-poor clades of the Maireana grade. The emergence of spine-like appendages and the onset of Sclerolaena diversification coincide with radiations of large herbivores, termites and ants. The spine-like appendages may have been a key innovation as protection against large herbivores, to reduce transpiration in hot environments, and with respect to dispersal by ants. In contrast to the wind-dispersed Maireana species, colonization of new habitats and migration between habitats may have been slower and on a smaller scale in Sclerolaena species. This reduced mobility may have resulted in lower gene flow and consequently may have favored a steady speciation rate, which is now apparent in the continuous cladogenesis of the species-rich Sclerolaena clade.
DDC: 570 Biowissenschaften
570 Life sciences
580 Pflanzen (Botanik)
580 Botanical sciences
Institution: Johannes Gutenberg-Universität Mainz
Department: FB 10 Biologie
Place: Mainz
URN: urn:nbn:de:hebis:77-openscience-fb0bc23a-65af-4c60-96d6-65cafe5b6bcc4
Version: Original work
Publication type: Dissertation
License: CC BY-SA
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Extent: 230 Seiten ; Illustrationen, Diagramme, Tabellen
Appears in collections:JGU-Publikationen

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