Abstract Detail

Systematics

Johnson, Melissa [1], Clark, John R. [2], McDade, Lucinda [1].

Phylogeny, biogeography, and diversification of Pacific Cyrtandra (Gesneriaceae), a hyper-diverse lineage of island specialists.

Aim: The angiosperm genus Cyrtandra (Gesneriaceae) is comprised of ca. 800 understory shrub/small tree species that are distributed throughout Southeast Asia and the Pacific. Although Cyrtandra is one of the largest (ca. 175 spp.) and most widespread genera of plants in the Pacific, little is known about the mechanisms driving this remarkable radiation of island specialists. The present study builds on previous phylogenetic work to: 1) evaluate relationships within and among the Pacific clades; 2) estimate when and where major lineages of Pacific Cyrtandra originated using advanced model-based approaches; and 3) examine the biogeographic processes that may have contributed to extant distributions. Methods: We sampled 160 accessions representing 114 taxa of Cyrtandra from across Southeast Asia and the Pacific, with an emphasis on Pacific archipelagos that host exceptional levels of species diversity. Three nuclear and two chloroplast markers were used to construct a well-resolved species phylogeny. Divergence times were estimated with BEAST, using maximum island ages as calibration points. Ancestral area estimations and biogeographic stochastic mapping (BSM) were done using the R package BioGeoBEARS. Results & Discussion: The resulting phylogenetic tree showed strong support values across the backbone, and for most major clades. Several areas in the Pacific are polyphyletic including the Solomon Islands, Vanuatu, Fiji, Samoa, and the Society Islands, while the Marquesas and Hawaii are monophyletic. The crown age of Cyrtandra is estimated to be 39 mya, with the Pacific lineage emerging 27 mya. Ancestral area estimation results indicate that the Pacific lineage of Cyrtandra likely originated in the Solomon Islands, followed by a single founder event to Fiji. From Fiji, six dispersal events expanded Cyrtandra's range to every major archipelago in the Pacific. The BSM results showed that all cladogenetic events in Pacific Cyrtandra involved jump dispersal.

1 - Claremont Graduate University, Botany, Rancho Santa Ana Botanic Garden, 1500 N. College Ave., Claremont, CA, 91711, USA
2 - Center for Plant Conservation National Headquarters, 15600 San Pasqual Valley Rd., Escondido, CA, 92027, USA

Keywords:
speciation
Pacific islands
Biogeography
phylogenetics
Fiji
founder events.

Presentation Type: Oral Paper
Session: 31, Cooley Awards II
Location: 201/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 2:30 PM
Number: 31005
Abstract ID:742
Candidate for Awards:George R. Cooley Award