Proposal
(525) to South
American Classification Committee
Resurrect the genus Uromyias
We propose the resurrection of the genus Uromyias based on recent molecular
phylogenetic evidence. Uromyias
should include the species currently classified as Anairetes agraphia and Anairetes
agilis, including subspecies therein. The appropriate placement of A. agraphia and A. agilis in relation to all other Anairetes species (Anairetes
sensu stricto) has been debated for
nearly a century (Hellmayr, 1927; Smith, 1971; Traylor, 1977; Lanyon, 1988; Roy
et al., 1999; DuBay and Witt, 2012). Hellmayr (1927) first placed A. agraphia and A. agilis into a distinct genus, Uromyias, based on morphological characters including a shorter,
wider, and more depressed bill, more developed rectal bristles, a
proportionately longer tail, and greater difference between the shortest and
longest rectrices. Lanyon (1988) concurred with the validity of the genus Uromyias based on cranial morphology;
specifically, Uromyias has a fully
ossified nasal septum and lacks posterior forking in the trabecular plate
that is characteristic of other Anairetes
species. Anairetes agraphia
and A. agilis are the only members of
the Anairetes group that are
restricted to extreme humid habitats (i.e. Chusquea
dominated cloud forest), whereas species in Anairetes
sensu stricto are all tolerant of drier and/or more seasonal environments.
Systematists who have favored merging Uromyias with Anairetes
have done so using justifications that we now know to be misguided or
incorrect. Smith (1971) rejected Uromyias
on the basis of his opinion that ecological differences should not delimit
generic boundaries. However, molecular phylogenies have since revealed that
habitats tend to be conserved across the tyrannid phylogeny (Ohlson et al.
2008). It follows that environmental characteristics are subject to
evolutionary inertia and are therefore appropriate for guiding classification.
Traylor (1977) subsequently favored dissolving Uromyias because the most recently described species, A. alpinus (Carriker 1933), appeared to
him to be morphologically intermediate between the two genera. We now know that
A. alpinus is phylogenetically nested
within Anairetes sensu stricto as
sister to the clade containing A.
flavirostris, A. parulus, and A. fernandezianus (Dubay and Witt 2012).
In 1999, Roy et al. provided the first molecular
phylogeny of Anairetes/Uromyias and
recovered the genus Uromyias nested
within Anairetes, albeit with weak
bootstrap support. Two separate analyses presented by Roy et al. (1999)
produced different phylogenetic positions for Uromyias, but Uromyias
was nested within Anairetes in both
topologies. It may have been underappreciated that neither of these alternative
analyses could statistically rule out the possibility that Uromyias is sister to a monophyletic Anairetes. Nonetheless, the analyses of Roy et al. (1999) provided
the impetus to merge the genus Uromyias
into Anairetes. The Roy et al. (1999)
phylogeny used short mtDNA fragments and parsimony and distance based methods.
In a recent study we revisited the phylogeny of this clade using improved taxon
sampling, seven
loci, 6407 base pairs, partitioned Bayesian analysis, species-tree methods, and
appropriate outgroups (DuBay and Witt, 2012).
The results decisively supported Uromyias and Anairetes as
reciprocally monophyletic sister clades with 100% posterior probability. Increasing the number of mtDNA characters alone
was sufficient to refute the Roy et al. (1999) hypothesis under parsimony, ML,
or Bayesian methods. Although individual nuclear genes were unable to resolve
the phylogeny, the multi-locus *BEAST species-tree method with seven loci
recovered the same result as the mtDNA alone.
In sum, it appears that previous justifications for merging
the two genera were guided by misconceptions about phylogeny and
underestimation of the evolutionary significance of the ecoclimatic niche. The
new phylogenetic results affirm the views of previous workers, including
Hellmayr (1927) and Lanyon (1988), that morphological and ecological
differences between the two clades warrant classification in separate genera.
Literature Cited:
DuBay,
S.G., Witt, C.C., 2012. An improved phylogeny of the Andean tit-tyrants (Aves,
Tyrannidae): More characters trump sophisticated analyses. Molecular
Phylogenetics and Evolution 64, 285-296.
Hellmayr,
C. E., 1927. Catalogue of birds of the Americas and the adjacent islands in
Field Museum of Natural History. Field Mus. Nat. Hist. Publ. 242 Zool. Ser. 13,
1-517.
Lanyon,
W. E., 1988. A phylogeny of the thirty-two genera in the Elaenia assemblage of
tyrant flycatchers. Am. Mus. Novit. 1-57.
Ohlson,
J., Fjeldså, J., Ericson, P. G. P., 2008. Tyrant flycatchers coming out in the
open: phylogeny and ecological radiation of Tyrannidae (Aves, Passeriformes).
Zool. Scripta 37, 315-335.
Roy,
M. S., Torres-Mura, J. C., Hertel, F., 1999. Molecular phylogeny and
evolutionary history of the tit-tyrants (Aves: Tyrannidae). Mol. Phylogen.
Evol. 11, 67-76.
Smith,
W. J., 1971. Behavioral characteristics of serpophaginine tyrannids. Condor 73,
259-286.
Traylor,
M. A. Jr., 1977. A classification of the tyrant flycatchers Tyrannidae. Bull.
Mus. Comparative Zool. 148, 129-184.
Shane G. DuBay and Christopher C. Witt,
June 2012
Comments from Stiles: “YES.
Genetic, morphological and distributional evidence all favor recognizing Uromyias.”
Comments from Pacheco: “YES. Published evidence supports
the proposal.”
Comments from Robbins: “YES,
although this comes down to subjective opinion, given that these (2 Uromyias
taxa + Anairetes sensu stricto) are sister clades, one could treat them
as members of the same genus.”
Comments from Cadena: “NO. The Dubay and Witt paper
reports on a very nice study, and I have no issue with the data and analyses.
But I agree with Mark that, considering that "Uromyias" and "Anairetes"
are sister groups, one could still treat them in a single genus. Doing that,
phylogenetic information is retained in classification by revealing a close
affinity between all the species in these two clades. Having them as separate
genera conveys information on relationships at a shallower phylogenetic level.
What is better? One could argue either way. Considering morphology and ecology,
I realize there might be good reasons for separating these species in two
genera, but I tend to prefer stability over taxonomic changes in cases like
this (unless both alternative classifications have been widely used off late,
such as in the Diglossa/Diglossopis case). In other words, given
the new data, changing the classification is not necessary so I say we keep it
as is.”
Comments from Stotz: “NO. This is a case very similar to Pipromorpha and Mionectes, where I voted no as well. If anything these two sister taxa seem less
well-differentiated than Pipromorpha
and Mionectes. The lump dates from the same time period, so
in the absence of a compelling reason to split Uromyias from Anairetes,
I have to support the status quo.”
Comments from Zimmer:
“YES. As pointed out by
Mark and Daniel, this really comes down to a matter of taste, as to how broadly
or narrowly one likes to define genera.
In this particular case, I don’t have really strong feelings either
way. However, as a general rule, I
prefer more internally cohesive, narrowly defined genera, and, on both
morphological and distributional grounds, Anairetes
sensu stricto would seem to be sufficiently distinct from agilis and agraphia to warrant generic separation. So, a somewhat tepid YES”.
Comments from Pérez-Emán: “YES. This is another proposal when we face the
issue of what to group within a genus and, as Daniel pointed out, what level of
information we want to include at this taxonomic level. We don’t have yet a
solution to this issue and it comes down to be a matter of taste. In this case,
previous to the Roy et al (1999) paper, most people agreed with keeping both Uromyias and Anairetes as separate genera based on bill, tail, and cranial
morphology. Lumping these taxa into Anairetes was a response to Roy et al.’s
results, an important study, but which could be considered an earlier version
of the molecular study done by DuBay and Witt (2012). As a more complete study
with similar characters does not support previous results (which were not
conclusive), I rather prefer to split these taxa into two genera than lumping
somehow divergent taxa into one genus (as a set aside thought, this course of
action might be leading us to consider a genus as a group of taxa with few
morphological and ecological differences compared to a larger and more diverse
inclusive genus).”
Comments from Jaramillo: “YES. I never understood why the two were
lumped, Uromyias looks and acts quite
unlike Anairetes. Minus the crest, Uromyias is as similar to Anairetes as Serpophaga to me, so resurrecting Uromyias sounds good to me.”
Comments from Nores: “YES. Although the reasons for joining or not joining these species are both valid, I prefer to separate them for three reasons: 1) they are quite different morphologically, 2) they dwell in very different habitats, and 3) new phylogenetic results suggest that morphological and ecological differences between the two clades warrant classification in separate genera.”