Historical biogeography of the widespread macroalga Sargassum (Fucales, Phaeophyceae)

Sargassum is a cosmopolitan brown algal genus spanning the three ocean basins of the Atlantic, Pacific and Indian Oceans, inhabiting temperate, subtropical and tropical habitats. Sargassum has been postulated to have originated in the Oligocene epoch approximately 30 mya according to a broad phyloge...

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Bibliographic Details
Published in:Journal of phycology Vol. 56; no. 2; pp. 300 - 309
Main Authors: Yip, Zhi Ting, Quek, Randolph Z. B., Huang, Danwei, Smith, J.
Format: Journal Article
Language:English
Published: United States Wiley Subscription Services, Inc 01.04.2020
John Wiley and Sons Inc
Subjects:
Algae
ancestral range
basins
Bayes Theorem
Bayesian analysis
Bayesian theory
Biogeography
brown macroalgae
Calibration
cladogenesis
Dispersal
Dispersion
Fossils
Fucales
genetic markers
Geographical distribution
global distribution
habitats
Indian Ocean
internal transcribed spacers
macroalgae
macroevolution
Marine environment
Miocene
Miocene epoch
Ocean basins
Oceans
Oligocene
Oligocene epoch
Phaeophyceae - genetics
Phylogeny
Phylogeography
Probability theory
Regular
Sargassum
Seaweed
Seaweeds
Spatial discrimination
Spatial resolution
time‐calibrated phylogeny
Tropical climate
Indian Ocean
time-calibrated phylogeny
macroevolution
ancestral range
cladogenesis
brown macroalgae
global distribution
ISSN:0022-3646, 1529-8817, 1529-8817
Online Access:Get full text
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Summary:Sargassum is a cosmopolitan brown algal genus spanning the three ocean basins of the Atlantic, Pacific and Indian Oceans, inhabiting temperate, subtropical and tropical habitats. Sargassum has been postulated to have originated in the Oligocene epoch approximately 30 mya according to a broad phylogenetic analysis of brown macroalgae, but its diversification to become one of the most widespread and speciose macroalgal genera remains unclear. Here, we present a Bayesian molecular clock study, which analyzed data from the order Fucales of the brown algal crown radiation (BACR) group to reconstruct a time‐calibrated phylogeny of the Sargassum clade. Our phylogeny included a total of 120 taxa with 99 Sargassum species sampled for three molecular markers – ITS‐2, cox3 and rbcLS – calibrated with an unambiguous Sargassaceae fossil from between the lower and middle Miocene. The analysis revealed a much later origin of Sargassum than expected at about 6.7 mya, with the genus diversifying since approximately 4.3 mya. Current geographic distributions of Sargassum species were then analyzed in conjunction with the time‐calibrated phylogeny using the dispersal‐extinction‐cladogenesis (DEC) model to estimate ancestral ranges of clades in the genus. Results strongly support origination of Sargassum in the Central Indo‐Pacific (CIP) region with subsequent independent dispersal events into other marine realms. The longer history of diversification in the ancestral CIP range could explain the much greater diversity there relative to other marine areas today. Analyses of these dynamic processes, when fine‐tuned to a higher spatial resolution, enable the identification of evolutionary hotspots and provide insights into long‐term dispersal patterns.
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ISSN:0022-3646
1529-8817
1529-8817
DOI:10.1111/jpy.12945