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Phylogenetic analysis of 1.5 Mbp and platypus EST data refute the Marsupionta hypothesis and unequivocally support Monotremata as sister group to Marsupialia/Placentalia

Kullberg, Morgan LU ; Hallström, Björn LU ; Arnason, Ulfur LU and Janke, Axel LU (2008) In Zoologica Scripta 37(2). p.115-127
Abstract
The extant mammalian groups Monotremata, Marsupialia and Placentalia are, according to the ‘Theria’ hypothesis, traditionally classified into two subclasses. The subclass Prototheria includes the monotremes and subclass Theria marsupials and placental mammals. Based on some morphological and molecular data, an alternative proposition, the Marsupionta hypothesis, favours a sister group relationship between monotremes and marsupials to the exclusion of placental mammals. Phylogenetic analyses of single genes and even multiple gene alignments have not yet been able to conclusively resolve this basal mammalian divergence. We have examined this problem using one data set composed of expressed sequence tags (EST) and another containing 1 510 509... (More)
The extant mammalian groups Monotremata, Marsupialia and Placentalia are, according to the ‘Theria’ hypothesis, traditionally classified into two subclasses. The subclass Prototheria includes the monotremes and subclass Theria marsupials and placental mammals. Based on some morphological and molecular data, an alternative proposition, the Marsupionta hypothesis, favours a sister group relationship between monotremes and marsupials to the exclusion of placental mammals. Phylogenetic analyses of single genes and even multiple gene alignments have not yet been able to conclusively resolve this basal mammalian divergence. We have examined this problem using one data set composed of expressed sequence tags (EST) and another containing 1 510 509 nucleotide (nt) sites from 1358 inferred cDNA genomic sequences. All analyses of the concatenated sequences unambiguously supported the Theria hypothesis. The Marsupionta hypothesis was rejected with high statistical confidence from both data sets. In spite of the strong support for Theria, a non-negligible number of single genes supported either of the two alternative hypotheses. The divergence between monotremes and therian mammals was estimated to have taken place 168–178 Mya, a dating compatible with the fossil record. Considering the long common evolutionary branch of therians, it is surprising that sequence data from many thousand amino acid sites were needed to conclusively resolve their relationship to monotremes. This finding draws attention to other mammalian divergences that have been taken as unequivocally settled based on much smaller alignments. EST data provide a comprehensive random sample of protein coding sequences and an economic way to produce large amounts of data for phylogenetic analysis of species for which genomic sequences are not yet available. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Zoologica Scripta
volume
37
issue
2
pages
115 - 127
publisher
Wiley-Blackwell
external identifiers
  • wos:000252963500001
  • scopus:38849093129
ISSN
0300-3256
DOI
10.1111/j.1463-6409.2007.00319.x
language
English
LU publication?
yes
id
c93574a1-228d-4e01-90c5-ac392f0f5139 (old id 989847)
date added to LUP
2008-01-29 12:34:04
date last changed
2017-01-01 05:13:27
@article{c93574a1-228d-4e01-90c5-ac392f0f5139,
  abstract     = {The extant mammalian groups Monotremata, Marsupialia and Placentalia are, according to the ‘Theria’ hypothesis, traditionally classified into two subclasses. The subclass Prototheria includes the monotremes and subclass Theria marsupials and placental mammals. Based on some morphological and molecular data, an alternative proposition, the Marsupionta hypothesis, favours a sister group relationship between monotremes and marsupials to the exclusion of placental mammals. Phylogenetic analyses of single genes and even multiple gene alignments have not yet been able to conclusively resolve this basal mammalian divergence. We have examined this problem using one data set composed of expressed sequence tags (EST) and another containing 1 510 509 nucleotide (nt) sites from 1358 inferred cDNA genomic sequences. All analyses of the concatenated sequences unambiguously supported the Theria hypothesis. The Marsupionta hypothesis was rejected with high statistical confidence from both data sets. In spite of the strong support for Theria, a non-negligible number of single genes supported either of the two alternative hypotheses. The divergence between monotremes and therian mammals was estimated to have taken place 168–178 Mya, a dating compatible with the fossil record. Considering the long common evolutionary branch of therians, it is surprising that sequence data from many thousand amino acid sites were needed to conclusively resolve their relationship to monotremes. This finding draws attention to other mammalian divergences that have been taken as unequivocally settled based on much smaller alignments. EST data provide a comprehensive random sample of protein coding sequences and an economic way to produce large amounts of data for phylogenetic analysis of species for which genomic sequences are not yet available.},
  author       = {Kullberg, Morgan and Hallström, Björn and Arnason, Ulfur and Janke, Axel},
  issn         = {0300-3256},
  language     = {eng},
  number       = {2},
  pages        = {115--127},
  publisher    = {Wiley-Blackwell},
  series       = {Zoologica Scripta},
  title        = {Phylogenetic analysis of 1.5 Mbp and platypus EST data refute the Marsupionta hypothesis and unequivocally support Monotremata as sister group to Marsupialia/Placentalia},
  url          = {http://dx.doi.org/10.1111/j.1463-6409.2007.00319.x},
  volume       = {37},
  year         = {2008},
}