Flora of the World

Publications (Showing 2 of 2)

Timing and tempo of evolutionary diversification in a biodiversity hotspot: Primulaceae on Indian Ocean islands

Joeri S. Strijk, Ruth E. Bone, Christophe Thébaud,

Journal of Biogeography

2013

Vol. 41, Issue 4

pp. 810-822

Aim

We examined phylogenetic relationships and spatio‐temporal diversification in Indian Ocean Primulaceae, assessing correlations between speciation rates, geographical expansion and ecomorphological specialization.

Location

Madagascar and Indian Ocean Islands.

Methods

We conducted phylogenetic analyses with plastid and nuclear

DNA

sequences of Primulaceae using maximum likelihood and Bayesian algorithms, and estimated divergence times using a Bayesian relaxed molecular clock. Temporal changes in diversification rate and possible correlations with the biogeographical history of the group were examined. We performed parametric ancestral area reconstruction incorporating a stratified palaeogeographical model that reflects changes in terrestrial configuration and the presence of phytogeographical connections through time in the western Indian Ocean Basin. Shifts in diversification rate were compared with ancestral area assignments and divergence age estimates.

Results

Indian Ocean Primulaceae were recovered as monophyletic with a sister relationship to Asian Ardisia. Oncostemum, a genus confined to Madagascar and the Comoros, was resolved as paraphyletic by the inclusion of a monophyletic Mascarene Badula group consisting of single‐island endemics. We found evidence for diversification bursts early in the history of Indian Ocean Primulaceae that correspond closely to the sequence of dispersal and the appearance of newly formed Mascarene Islands. Age estimates suggest a dispersal to Rodrigues that is older than the estimated geological age of the island.

Main conclusions

Results suggest a Madagascan origin of Indian Ocean Primulaceae with subsequent dispersal to the Mascarenes in the middle to late Miocene, with initial establishment on either Mauritius or Rodrigues and subsequent stepping‐stone dispersal to the other two Mascarene islands within the last 2 Myr. Analyses suggest that diversification has slowed over time, with significant rate changes following dispersal to new geographical areas. Onset of diversification in species‐rich Oncostemum appears to have been recent, with major cladogenesis commencing in the early Pliocene.

DOI:

10.1111/jbi.12259

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Phylogenetic inference of Badula (Primulaceae), a rare and threatened genus endemic to the Mascarene Archipelago

Ruth E. Bone, Joeri S. Strijk, Peter W. Fritsch,

Botanical Journal of the Linnean Society

2012

Vol. 169, Issue 2

pp. 284-296

With 14 species, Badula (Primulaceae) is the most species-rich endemic angiosperm genus of the Mascarene Archipelago. The relationship between Badula and its ally Oncostemum (c. 100 spp; Madagascar and the Comoros Islands) is uncertain, with implications for the circumscription of Badula as a Mascarene endemic. Within Badula, species rarity (several being critically endangered) and a paucity of herbarium specimens hamper proper species delimitations. Here, we estimate the phylogenetic relationships of Badula based on DNA sequence data from the nuclear ribosomal internal transcribed spacer (ITS) and plastid trnS-trnG-trnG regions with complete taxon sampling of the genus and three samples or more of each taxon. The results strongly supported the monophyly of Badula. Paraphyly of Oncostemum was inferred with weak support; explicit hypothesis testing did not favour this hypothesis over one that forced the monophyly of Oncostemum. Monophyly of several Badula spp. was supported, particularly for taxa from the older islands of Mauritius and Rodrigues. Badula is inferred to have reached the Mascarene Archipelago through a single colonization event. The majority of species segregated into island clades, implying that few, rather than multiple, colonization events have occurred in Badula among the islands of the archipelago.

DOI:

10.1111/j.1095-8339.2012.01221.x

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