phylogenetic relationships and classification of didelphid marsupials ...
phylogenetic relationships and classification of didelphid marsupials ...
phylogenetic relationships and classification of didelphid marsupials ...
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78 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 322<br />
Fig. 34. Alternative resolutions for three patterns <strong>of</strong> intergeneric <strong>relationships</strong> that exhibit nodal<br />
posterior probabilities ,0.95 in the Bayesian analysis <strong>of</strong> the concatenated five-gene dataset (see fig. 33). A,<br />
B, C, alternative <strong>relationships</strong> among Glironia, Hyladelphys + Didelphinae, <strong>and</strong> Caluromys +<br />
Caluromysiops; D, E, F, alternative <strong>relationships</strong> among Tlacuatzin, Marmosa, <strong>and</strong>Monodelphis; G, H,<br />
I, alternative <strong>relationships</strong> among Cryptonanus, Thylamys + Lestodelphys, <strong>and</strong>Gracilinanus. Black <strong>and</strong><br />
grey circles at nodes indicate posterior probabilities $0.95 or ,0.95, respectively. Branch lengths are<br />
shown at the same scale across all trees.<br />
(from 80% to 93%), as does the Bayesian<br />
posterior probability for placing the ingroup<br />
root between (Glironia (Caluromys + Caluromysiops))<br />
<strong>and</strong> other <strong>didelphid</strong>s (from 0.51 to<br />
0.87). Similarly, adding nonmolecular characters<br />
marginally improves the Bayesian<br />
posterior probability for Marmosa + Tlacuatzin<br />
(from 0.63 to 0.83).<br />
By contrast, including Chacodelphys in a<br />
combined-data parsimony analysis dramatically<br />
erodes bootstrap support for five<br />
intergeneric nodes (fig. 36). In fact, the strict<br />
consensus <strong>of</strong> 12 minimum-length trees (not<br />
shown) places Chacodelphys as the sister<br />
group <strong>of</strong> Monodelphis with weak (MPBS 5<br />
49%) support. Bayesian analysis, however,<br />
strongly supports the membership <strong>of</strong> Chacodelphys<br />
in a clade that also includes Gracilinanus,<br />
Cryptonanus, <strong>and</strong>Thylamys + Lestodelphys,<br />
<strong>and</strong> posterior probabilities for other<br />
nodes are substantially unaffected by taxon<br />
addition.<br />
Discussion<br />
Analyses <strong>of</strong> our combined dataset (excluding<br />
Chacodelphys; fig. 35) effectively summarize<br />
all <strong>of</strong> the shared <strong>phylogenetic</strong> signal that<br />
we have found to date in morphology,<br />
karyotypes, <strong>and</strong> five unlinked protein-coding<br />
nuclear genes. Additional support is provided<br />
by 16 parsimony-informative indels (figs. 29,<br />
30, 31) that were not coded as <strong>phylogenetic</strong><br />
characters but which optimize as synapomorphies<br />
on this topology. Lastly, this tree is<br />
congruent with the results <strong>of</strong> independent<br />
<strong>phylogenetic</strong> analyses based on sequence data<br />
from intron 1 <strong>of</strong> the nuclear transthyretin<br />
(TTR) gene <strong>and</strong> the mitochondrial 12S<br />
rDNA gene (Steiner et al., 2005). To the best
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