MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Ancient protein sequencing resolves litoptern and notoungulate superordinal affinities
Autor/es:
MCPHEE, R.; WELKER, F.; THOMAS, J.; BRACE, S.; CAPPELLINI, E.; TURVEY, S.; BARNES, I.; REGUERO, M.; GELFO, J.; KRAMARZ, A.
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress; 2014
Institución organizadora:
International Paleontological Association
Resumen:
Recent speculations
concerning the affinities of South American native ungulates (SANUs)
assert that at least some members of
this ?paraphyletic group are not laurasiatheres but are instead either sister to Afrotheria or part of a distinct
clade that includes afrotheres. Testing of this controversial hypothesis is
desirable, optimally with data independent of phenotypic interpretation. Such a
test might come from molecular data using short DNA sequences as barcodes (cf.
Barcode of Life), but all efforts to acquire such information from SANU fossils
have so far failed. There is an alternative: backbones of proteins such as
collagen are an order of magnitude more stable than DNA and therefore more likely
to survive taphonomically. We screened 34 Pleistocene bone samples of Toxodon
(Notoungulata) and Macrauchenia (Litopterna) for collagen and DNA.
Autochthonous DNA was not recovered, but collagen yield was often excellent.
Using soft-ionization tandem mass spectrometry we obtained >90% sequence
coverage of COL1α1 and COL1α2 sequences (1057 and 1040 residues, respectively)
on the 4 best samples (2 per taxon), yielding 21,428 matching spectra. Aligned
fossil sequences were mapped onto a mammalian phylogeny based on collagen gene
transcripts from available genomes and MS/MS collagen data obtained for this
study or from the literature. Our collagen tree yielded conventional
Afrotheria, Euarchontoglires, Xenarthra, and Laurasiatheria, in overall good
agreement with recent genomic and phenomic phylogenies of Placentalia. The two
SANU taxa invariably placed within Euungulata, as follows: (((Toxodon,
Macrauchenia) (Perissodactyla))(Cetartiodactyla)). Thus representative
notoungulate and litoptern taxa fall on this evidence within Laurasiatheria and
adjacent to crown Perissodactyla, at the opposite end of the cladogram from
Afrotheria. This is consistent with the longstanding view that at least some
SANU lineages may have originated from northern archaic ungulates
(?condylarths?). To further test SANU affinities and their possible monophyly
(as so-called ?meridiungulates?), analyses of representative Astrapotheria,
Xenungulata, and Pyrotheria would be needed. With improvements in
instrumentation and analytical procedures, proteomics may produce a revolution
in systematics like that achieved by DNA genomics, but with the possibility of
working on much deeper timescales. [Partly supported by SYNTAX award ?Barcode
of Death? & NSF OPP 1142052].