Format: ORAL

Jay Edneil C. Olivar1, Frank Hauenschild1,4, Hannah J. Atkins2, Gemma L.C. Bramley3, Alexandra N. Muellner-Riehl1,5

1 Department of Molecular Evolution and Plant Systematics & Herbarium (LZ), Institute of Biology, Leipzig University, Johannisallee 21-23, D-04103 Leipzig, Germany 2 Royal Botanic Garden Edinburgh, 20a Inverleith Row, EH3 5LR, United Kingdom 3 Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, United Kingdom 4 Centre for Teacher Training and School Research, Leipzig University, Prager Str. 38–40, D-04317 Leipzig, Germany 5 German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Puschstrasse 4, D-04103 Leipzig, Germany

The general dynamic model of oceanic island biogeography (GDM) views oceanic islands predominantly as sinks rather than sources of dispersing lineages. To test this, we conducted a biogeographic analysis of a highly successful insular plant taxon, Cyrtandra, and inferred directionality of dispersal and founder events throughout the four biogeographical units of the Indo-Australian Archipelago (IAA), namely Sunda, Wallacea, Philippines, and Sahul. Sunda was recovered as the major source area, followed by Wallacea. The relatively high number of dispersal and founder events originating from Wallacea is attributed to its central location in the IAA and its complex geological history selecting for increased dispersibility in Cyrtandra. We also tested if early diversification dynamics in Cyrtandra follow predictions of adaptive radiation, which is the dominant process on oceanic islands as per the GDM. Diversification dynamics of dispersing lineages of Cyrtandra in the Southeast Asian grade showed early bursts in diversification rates followed by a plateau which is consistent with adaptive radiation. We did not detect signals of diversity-dependent diversification and this is attributed to Southeast Asian cyrtandras occupying various niche spaces as evident by its wide morphological range, particularly in habit and floral characters. The clade containing mostly Pacific members, which arrived at the early stages of the ontogeny of the Pacific Islands, showed diversification dynamics predicted by the Island Immaturity Speciation Pulse (IISP) model and their morphological range is controlled by the least action effect favoring woodiness and fleshy fruits. Our study provides a first step towards a framework for investigating early diversification dynamics as predicted by GDM in highly successful insular taxa.