phylogenetic relationships and classification of didelphid marsupials ...

76 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 322
TABLE 14
Support for Generic Monophyly from Single-gene Datasets a
hard incongruence among patterns of intergeneric
relationships supported individually
by these loci concerns the relationships of
Cryptonanus. This obviously problematic
taxon was recovered with strong nodal
support either as the sister group of Gracilinanus
emiliae (in all analyses of DMP1), or as
the sister group of Gracilinanus (in all analyses
of RAG1), or as the sister group of Thylamys
+ Gracilinanus (in all analyses of vWF).
Analyses of Concatenated Genes
Maximum parsimony, maximum likelihood,
and Bayesian analyses of concatenated
sequence data from all five genes (7320 bp)
resulted in well-resolved and strikingly similar
trees with high support values at most
nodes (fig. 33). Among other analytic similarities,
all polytypic genera were recovered
as monophyletic groups, as were all of the
higher-level clades common to two or more
of the single-gene analyses discussed above.
However, three intergeneric nodes remain
weakly or inconsistently supported.
The first of these concerns the position of
the ingroup root. Whereas maximum parsimony
weakly supports placing the root
between Glironia and other didelphids (which
were recovered as a monophyletic group with
a bootstrap frequency of 74%), maximum
likelihood places the root between (Glironia
(Caluromys + Caluromysiops)) and Hyladelphys
+ Didelphinae; however, likelihood
bootstrap support for the former group is
weak (,50%). Bayesian posterior probabilities
for three alternative placements of the
IRBP DMP1 RAG1 BRCA1 vWF
Caluromys ** ** NR ** **
Cryptonanus ** ** ** ** **
Didelphis NR ** NR NR NR
Gracilinanus R NR ** ** **
Marmosa ** ** ** ** **
Marmosops ** ** * ** **
Monodelphis ** ** * ** **
Philander ** ** NR ** NR
Thylamys ** * * ** **
a
Key: ** 5 strong support from all analyses (MP, ML, Bayesian); * 5 strong support from at least one analysis; R 5
recovered without strong support; NR 5 not recovered.
ingroup root (fig. 34A, B, C) suggest that the
parsimony and likelihood solutions are almost
equiprobable but slightly favor the
latter.
The second equivocal node concerns the
relationships of Marmosa, Tlacuatzin, and
Monodelphis. Although Marmosa and Tlacuatzin
were recovered as sister taxa, support
for this clade was uniformly weak. Bayesian
posterior probabilities for all possible resolutions
of this node (fig. 34D, E, F), however,
suggest a somewhat clearer ranking than was
obtained for alternative placements of the
ingroup root.
The third problematic issue concerns
relationships among Gracilinanus, Cryptonanus,
and Thylamys + Lestodelphys. Here,
parsimony provides moderate bootstrap support
(58%) for grouping Gracilinanus with
Cryptonanus as does likelihood (70%). Although
Bayesian support for Gracilinanus +
Cryptonanus is weak, posterior probabilities
clearly favor this clade over other phylogenetic
alternatives (fig. 34G, H, I).
Analyses of Combined Datasets
Maximum parsimony and Bayesian analyses
of the combined (nonmolecular +
molecular) data without Chacodelphys recover
the same higher-level topologies that were
obtained from analyses of the concatenatedgene
data, with only a few noteworthy
changes in nodal support (fig. 35). For
example, parsimony bootstrap support for
the monophyly of Didelphis increases slightly
when nonmolecular character data are added