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Protostomia Phylogeny

It is based primarily on the articles of Halanych et al. (Science 1995) and Aguinaldo et al. (Nature 1997) as well as on the spectacular tree of life phylogeny created by David M. Hillis, Derrick Zwickl, and Robin Gutell, University of Texas.
by

Lisa Ulrich

on 28 January 2014

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Transcript of Protostomia Phylogeny

“There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

--Charles Darwin, 1859
Winnebeck
et al.
, 2010,
Journal of Insect Science
18S rDNA resolves Mysteries of Protostomia Phylogeny
(Halanych
et al.
, 1995,
Science
& Aguinaldo
et al.
, 1997,
Nature
)
Previous classifications of Lophophorates
monophyletic
subkingdom, superphylum or phylum, due to similar suspension-feeding apparatus (lophophore)
as
protostomes
on basis of presence of chitin, lack of sialic acid & embryological features as well as
incomplete
18S rDNA data
as
basal deuterostomes
after reanalyses of embryology (blastopore fate, coelom formation, cleavage patterns) & morphology
as protostomes, deuterostomes, as members of both groups or as an independent metazoan lineage
Reconstruction of lophophorate evolution
Sequencing of
complete
18S rDNA of representative lophophorate taxa
Alignment with existing data from other metazoan taxa
Analysis with standard phylogenetic techniques
Tree reconstruction methods
Sequence-based methods

Maximum Likelihood
Maximum Parsimony
Distance-based methods

Neighbor-Joining with estimates of Kimura-2-Parameter distances
paralinear distances (LogDet)
Jukes-Cantor distances
3.
Analyzed organisms in modern phylogenetic trees based on 18S rRNA
Opisthokonta
Fungi
Ctenophora & Porifera
Cnidaria
Placozoa
Bilateria
Rotifer
Metazoa
Nematode
Nematomorph
rapidly evolving nematode sequences
Rotifer, Nematomorpha & Nematoda
Platyhelminth
Platyhelminthes
Chordate
Vertebrate
Echinoderm
Deuterostomia
Bryozoan
Annelid
Phoronid
Brachiopod
Bryozoa
Annelida
Brachiopod
Mollusks
Onychophoran
Tardigrades
Phoronida & Brachiopoda
Mollusca
Lophotrochozoa
Ecdysozoa
Arthropod
Arthropod
Arthropoda
Ornychophora & Tardigrada
1.
Lophotrophozoa as one of the two protostomian clades
Jukes-Cantor-Model


Mutation rate for every nucleotide is the same
Kimura-2-Parameter-Model

Transition is chemically easier then Transversion
Maximum Parsimony

Tree with the minimal number of substitution events is favored
Tree with the minimal Tree Length
Topology?
Maximum Likelihood

Tree with the maximized likelihood is favored
constant substitution rate
Topology!
Neighbor-Joining

for additive (= weighted binary) trees with no constant evolutionary rate
neighboring nods are replaced by a parental nod
Bootstrapping
18S rDNA consensus tree
Outgroups
Halanych
et al.
, 1995,
Science
Common ancestor shared by Lophophorates, Mollusks & Annelids
Halanych
et al.
, 1995,
Science
Conclusions

Separation of the monophyletic clade Protostomia into 2 groups: Lophotrochozoa & Ecdysozoa

Embryological features more plastic than traditionally recognized

Phylogentic position of flatworms important for theory of Bilateria evolution

C. elegans
(nematode) &
Drosophila
(arthropod) more closely related than traditionally indicated

Loss of chitin synthesis as a synapomorphy to deuterostomes

Segmentation probably not a synapomorphy uniting arthropods and annelids
2.
Ecdysozoa (moulting animals) as the second protostomian clade
Analyses of arthropods' relationships to other metazoan taxa
Confirmation of relationships with taxa such as tardigrades or onychophorans
Nematodes as close relatives to arthropods?
Problem with molecular phylogeny of nematodes
Including rapidly evolving sequences
Excluding rapidly evolving sequences
Aguinaldo
et al.
, 1997,
Nature
Aguinaldo
et al.
, 1997,
Nature
Biletaria
Protostomia
Substitution rates of 18S rDNA sequences
Aguinaldo
et al.
, 1997,
Nature
18S rDNA consensus tree indicating two protostomian clades
Aguinaldo
et al.
, 1997,
Nature
Moulting animals
Lophotrochozoa
18S rDNA consensus tree including slowly evolving flatworm sequences
Aguinaldo
et al.
, 1997,
Nature
Lophotrochozoa
Moulting animals
Consensus tree resolving the mystery of division within Protostomia
Aguinaldo
et al.
, 1997,
Nature
Hillis
et al.
, 2003,
Science

Hillis
et al.
Thank you!
Full transcript