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Phylogenetic position and biogeography of the Madagascar-centered tribe Danaideae (Rubiaceae: Rubioideae).
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The Western Indian Ocean Region (WIOR) is a biodiversity hotspot with a very large number of endemic taxa. The islands in the region differ in age, size and geological history, making a unique area and interesting place for studying biogeographic patterns. It has been shown in several studies that Africa is the main source of the Malagasy flora, and that transoceanic dispersal is the most common colonization mechanism in the WIOR. Here, we examine the phylogenetic position and biogeographical history of the Madagascar-centered tribe Danaideae of subfamily Rubioideae (Rubiaceae). Previous studies showed conflicting topologies regarding the phylogenetic position of the tribe, implying contradicting biogeographical hypotheses. In our study Danaideae is resolved as sister to a subclade of the Spermacoceae alliance consisting of the two tribes Knoxieae and Spermacoceae. The ancestor of Danaideae is inferred to have been distributed in Africa and to have dispersed to Madagascar between 49.67 Mya and 13.47 Mya, where the crown group of Danaideae emerged 13.47 Mya. The tribe diversified in Madagascar and later colonized the neighboring islands: once to the Comoros in the northwest, and once to the Mascarenes in the east. The single species occurring in Tanzania is the result of a later long distance dispersal event from Madagascar to Africa. The dispersal events all took place in the Pliocene (from 5.3 Mya) and onwards, when Madagascar had become subject to both the northwestern Indian Monsoons and southeastern trade winds, which could facilitate dispersal events in both directions. Our results are consistent with several other studies, showing an African origin for the Malagasy flora and Madagascar being the main place of origin for plant species on the neighboring islands.

 

National Category
Botany
Research subject
Plant Systematics
Identifiers
URN: urn:nbn:se:su:diva-98613OAI: oai:DiVA.org:su-98613DiVA: diva2:684630
Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2014-01-10
In thesis
1. Systematics and Biogeography of Western Indian Ocean Region Rubiaceae: examples from Danaideae, Hymenodictyeae, and Naucleeae
Open this publication in new window or tab >>Systematics and Biogeography of Western Indian Ocean Region Rubiaceae: examples from Danaideae, Hymenodictyeae, and Naucleeae
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the systematics and biogeography of the tribes Danaideae, Hymenodictyeae, and Naucleeae in the angiosperm family Rubiaceae (coffee family), with a special interest in the Western Indian Ocean region (WIOR). The levels of endemism in the WIOR are remarkably high and Madagascar is the largest island surrounded by three main archipelagos with islands of various age and size. Rubiaceae is one of the species-rich families in the region, rendering it a suitable group for addressing evolutionary and biogeographic questions.

Danaideae consists of the two Malagasy endemic genera Payera and Schismatoclada, and the WIOR-centered Danais. The monophyly and generic delimitations of the tribe were tested with molecular data. The tribe was strongly supported as monophyletic, and resolved in two well-supported clades: the Danais and Payera-Schismatoclada clade. The ancestor of Danaideae was inferred to have dispersed from continental Africa to Madagascar, where the major diversification of the tribe took place in the Late Miocene to Pliocene. Danais colonized the neighbouring archipelagos between 6.54 and 2.98 Mya, and recolonized continental Africa once.

The predominantly Paleotropical sister tribes Hymenodictyeae and Naucleeae belong to the mainly Neotropical subfamily Cinchonoideae. The monophyly of the Hymenodictyeae genera, Hymenodictyon and Paracorynanthe, received strong support. Naucleeae consists of 26 genera divided in seven subtribes. All subtribes were resolved as monophyletic, while seven genera are paraphyletic; as a result, we recognize 17 genera. Both our results and the fossil record support the hypothesis of a boreotropical distribution for the ancestor of the Hymenodictyeae-Naucleeae clade. All dispersal events in the WIOR took place in the Miocene or later. The Malagasy species were the result of separate dispersal events from Africa and Gyrostipula comorensis endemic to the Comoros is the result of a single dispersal event from Madagascar.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2014. 41 p.
National Category
Botany
Research subject
Plant Systematics
Identifiers
urn:nbn:se:su:diva-98516 (URN)978-91-7447-832-7 (ISBN)
Public defence
2014-02-14, Lecture Hall, Department of Ecology, Environment and Plant Sciences, Lilla Frescativägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense the following papers were unpublished and had a status as follows: Paper 2: Manuscript; Paper 3: Manuscript; Paper 4: Manuscript

Available from: 2014-01-23 Created: 2014-01-07 Last updated: 2014-01-24Bibliographically approved

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