ORIGIN AND RAPID DIVERSIFICATION OF A TROPICAL MOSS

ORIGIN AND RAPID DIVERSIFICATION OF A TROPICAL MOSS Abstract Molecular sequences rarely evolve at a constant rate. Yet, even in instances where a clock can be assumed or approximated for a particular set of sequences, fossils or clear patterns of vicariance are rarely available to calibrate the clock. Thus, obtaining absolute timing for diversification of natural lineages can prove difficult. Unfortunately, without absolute time we cannot develop a complete understanding of important evolutionary processes, including adaptive radiations and key innovations. In the present study, the coding sequence of the nuclear gene, glyceraldehyde 3‐phosphate dehydrogenase (gpd), extracted from the paleotropical moss, Mitthyridium, was found to exhibit clocklike behavior and used to reconstruct the history of 80 distinct molecular lineages that cover the full geographic range of Mitthyridium. Two separate clades endemic to two geographically distinct oceanic archipelagos were revealed by this phylogenetic analysis. This allowed the use of island age (as derived from potassium‐argon dating) as a maximum age of origin of each monophyletic group, providing two independent time anchors for the clock found in gpd, the final piece needed to study absolute time. Based on results from both maximum age calibrations, which separately yielded highly consistent estimates, the ancestor of this moss group arose approximately 8 million years ago, and then diversified at the rapid rate of 0.56 ± 0.004 new lineages per million years. Such a rate is on par with the highest diversification rates reported in the literature including rapidly radiating insular groups like the Hawaiian silversword alliance, a classic example of an adaptive radiation. Using independent sources of data, it was found that neither the age nor diversification estimates were affected by the use of molecular lineages rather than species as the operational taxonomic units. Identifying the cause for this rapid diversification requires further testing, but it appears to be related to a general shift in reproductive strategy from sexual to asexual, which may be a key innovation for this young group. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Evolution Wiley

ORIGIN AND RAPID DIVERSIFICATION OF A TROPICAL MOSS

Evolution, Volume 59 (7) – Jul 1, 2005

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Publisher
Wiley
Copyright
Copyright © 2005 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0014-3820
eISSN
1558-5646
DOI
10.1111/j.0014-3820.2005.tb01792.x
Publisher site
See Article on Publisher Site

Abstract

Abstract Molecular sequences rarely evolve at a constant rate. Yet, even in instances where a clock can be assumed or approximated for a particular set of sequences, fossils or clear patterns of vicariance are rarely available to calibrate the clock. Thus, obtaining absolute timing for diversification of natural lineages can prove difficult. Unfortunately, without absolute time we cannot develop a complete understanding of important evolutionary processes, including adaptive radiations and key innovations. In the present study, the coding sequence of the nuclear gene, glyceraldehyde 3‐phosphate dehydrogenase (gpd), extracted from the paleotropical moss, Mitthyridium, was found to exhibit clocklike behavior and used to reconstruct the history of 80 distinct molecular lineages that cover the full geographic range of Mitthyridium. Two separate clades endemic to two geographically distinct oceanic archipelagos were revealed by this phylogenetic analysis. This allowed the use of island age (as derived from potassium‐argon dating) as a maximum age of origin of each monophyletic group, providing two independent time anchors for the clock found in gpd, the final piece needed to study absolute time. Based on results from both maximum age calibrations, which separately yielded highly consistent estimates, the ancestor of this moss group arose approximately 8 million years ago, and then diversified at the rapid rate of 0.56 ± 0.004 new lineages per million years. Such a rate is on par with the highest diversification rates reported in the literature including rapidly radiating insular groups like the Hawaiian silversword alliance, a classic example of an adaptive radiation. Using independent sources of data, it was found that neither the age nor diversification estimates were affected by the use of molecular lineages rather than species as the operational taxonomic units. Identifying the cause for this rapid diversification requires further testing, but it appears to be related to a general shift in reproductive strategy from sexual to asexual, which may be a key innovation for this young group.

Journal

EvolutionWiley

Published: Jul 1, 2005

References

  • Historical biogeography of the cicadas of Wallacea, New Guinea and the West Pacific: a geotectonic explanation
    Boer, Boer; Duffels, Duffels
  • Phylogenies from molecular sequences: inference And reliability
    Felsenstein, Felsenstein
  • Radiation in the Cape flora and the phylogeny of peacock irises Moraea (Iridaceae) based on four plastid DNA regions
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  • Examining rates and patterns of nucleotide substitution in plants
    Muse, Muse
  • Inferring speciation rates from phylogenies
    Nee, Nee
  • r8s: inferring absolute rates of molecular evolution and divergence times in the absence of a molecular clock
    Sanderson, Sanderson
  • Phylogenetic evidence of a rapid radiation of pleurocarpous mosses (Bryophyta)
    Shaw, Shaw; Cox, Cox; Goffinet, Goffinet; Buck, Buck; Boles, Boles
  • Pairwise comparison of mitochondrial DNA sequences in stable and exponentially growing populations
    Slatkin, Slatkin; Hudson, Hudson
  • Use of the nuclear gene glyceraldehyde 3‐phosphate dehydrogenase for phylogeny reconstruction of recently diverged lineages in Mitthyridium (Musci: Calymperaceae)
    Wall, Wall

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