Re-Evaluation of Phylogenetic Relationships among Species of the Mangrove Genus Avicennia from Indo-West Pacific Based on Multilocus Analyses.

Xinnian Li,Lishi Huang,Zhang Zhang,Yelin Huang,Yuxiang Zhu,Yuchen Yang,Norman C Duke,Cairong Zhong,Renchao Zhou,Suhua Shi

doi:10.1371/journal.pone.0164453

Abstract

Avicennia L. (Avicenniaceae), one of the most diverse mangrove genera, is distributed widely in tropical and subtropical intertidal zones worldwide. Five species of Avicennia in the Indo-West Pacific region have been previously described. However, their phylogenetic relationships were determined based on morphological and allozyme data. To enhance our understanding of evolutionary patterns in the clade, we carried out a molecular phylogenetic study using wide sampling and multiple loci. Our results support two monophyletic clades across all species worldwide in Avicennia: an Atlantic-East Pacific (AEP) lineage and an Indo-West Pacific (IWP) lineage. This split is in line with biogeographic distribution of the clade. Focusing on the IWP branch, we reconstructed a detailed phylogenetic tree based on sequences from 25 nuclear genes. The results identified three distinct subclades, (1) A. rumphiana and A. alba, (2) A. officinalis and A. integra, and (3) the A. marina complex, with high bootstrap support. The results strongly corresponded to two morphological traits in floral structure: stigma position in relation to the anthers and style length. Using Bayesian dating methods we estimated diversification of the IWP lineage was dated to late Miocene (c. 6.0 million years ago) and may have been driven largely by the fluctuating sea levels since that time.

Highlights

Avicennia L., an important component of forests worldwide in tropical and subtropical intertidal zones [1, 2], is currently thought to be derived from within the Acanthaceae based on recent phylogenetic studies (APG III, [3, 4]), it has been placed in Verbenaceae or Avicenniaceae in some classifications
We address the following questions: (1) Do molecular data support a phylogenetic grouping based on geographical distributions of Atlantic-East Pacific (AEP) and Indo-West Pacific (IWP) lineages? (2) What are the phylogenetic relationships of the five IWP Avicennia species and what do they tell us about evolution of flower characters? (3) When did the IWP Avicennia species diversify and what was the possible driving force behind this divergence? Our results shed fresh light on the evolution of this important mangrove clade and should enable further studies of this group’s remarkable adaptation to the intertidal environment
In the combined chloroplast tree, species of Avicennia fell into two clades: five in the IWP region forming one clade and the remaining three in the AEP region forming the other (S2 and S3 Figs; Posterior Probability P = 1.00 for Bayesian Inference (BI); Bootstraps BS = 100% and 99% for maximum likelihood (ML) and maximum parsimony (MP), respectively)

Summary

Introduction

Avicennia L., an important component of forests worldwide in tropical and subtropical intertidal zones [1, 2], is currently thought to be derived from within the Acanthaceae based on recent phylogenetic studies (APG III, [3, 4]), it has been placed in Verbenaceae or Avicenniaceae in some classifications. Avicennia has developed several unique features, such as salt glands, aerial and prop roots and finger-like pneumatophores, and cryptoviviparous fruits with the ability to float in salt water [2]. Members of the genus often occupy newly-formed seaward mangrove habitats on tropical coasts. Molecular Phylogeny of Genus Avicennia design, data collection and analysis, decision to publish, or preparation of the manuscript

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Discussion

Conclusion