Abstract Detail

Biogeography

Appelhans, Marc [1], Wagner, Warren [2], Wen, Jun [3].

Historical biogeography of Melicope (Rutaceae): Diversification rates and Pacific dispersal routes.

Because of their wide distributions, which range from mainland SE Asia, the Malesian region, and Australasia, to many Pacific archipelagos (and Madagascar in Melicope), the genera Acronychia, Euodia and Melicope (Rutaceae) are ideal examples to study Asian and Pacific biogeography. The center of species richness and endemicity of all three genera is New Guinea but the genera differ greatly in terms of species richness (Acronychia: 48 spp., Euodia: 7 spp., and Melicope: about 230 spp.). Our molecular phylogenetic studies show that Melicope and Acronychia are closely related and that Euodia is sister to both. Molecular dating analyses suggest that the Acronychia – Melicope clade and the Euodia clade might have evolved in the late Oligocene to early Miocene and that their geographical origin is Australasia. Considering the similar age of the Acronychia – Melicope clade and the Euodia clade, the differences in species richness are striking. Two clear accelerations in diversification rates can be observed in the phylogenetic tree. The first acceleration corresponds to the colonization of the Hawaiian Islands where Melicope underwent an adaptive radiation that made Melicope the most species-rich genus of woody plants on the archipelago. The second acceleration correlates to the Acronychia clade, in which many narrow endemics in New Guinean mountain ranges can be found. The differences in species richness and diversification rates between the Acronychia – Melicope clade and the Euodia clade might be explained by differences in fruit and seed morphology. Euodia seeds have a brittle seed coat and seeds are elastically discharged from the opening fruit. Melicope, in contrast, has a nutritious outer seed coat layer and a thick inner layer and the seeds remain attached to open fruits. Acronychia has drupaceous fruits and shares the seed coat characteristics with Melicope. The fruit and seed coat characteristics of Acronychia and Melicope are adaptations to bird dispersal. In this way, especially Melicope reached distant regions such as Madagascar and Hawai´i while Euodia remained restricted to New Guinea, Northern Australia and nearby archipelagos. By including species from all Pacific archipelagos we were able to reconstruct Pacific dispersal routes. Several dispersal events into the Pacific can be observed within Melicope, and most lineages are of Australian or New Guinean descent. Most interestingly, Melicope colonized the isolated Austral Islands twice independently and two dispersal events from the Hawaiian Islands to the Marquesas Islands were inferred.

1 - University of Goettingen, Systematic Botany, Untere Karspuele 2, Goettingen, 37073, Germany
2 - Smithsonian Institution, Botany, MRC-166 National Museum Of Natural History, PO Box 37012, Washington, DC, 20013-7012, USA
3 - Smithsonian Institution, Botany, MRC-166 National Museum Of Natural History, 10th St. & Constitution Ave., NW, MRC 166, Washington/DC, N/A, 20013-7012, USA

Keywords:
Phylogeny
biogeography
Rutaceae
Melicope
Pacific
SE Asia
Hawaii.

Presentation Type: Oral Paper:Papers for Topics
Session: 59
Location: Salon 3/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 8:00 AM
Number: 59001
Abstract ID:64
Candidate for Awards:None