Proposal (235) to South American Classification Committee
classification of the Formicariidae
Background: This proposal would revise the family-level
classification of the Formicariidae, which as currently defined is not a
Currently, the Formicariidae includes species in the following
New Information: Several recent studies
(Irestedt et al. 2002, Chesser 2004, Rice 2005a, 2005b) have assessed the
relationships among these genera and genera of other suboscine families based
on mitochondrial (cytochrome b, ND2, ND3, COI) and nuclear (cmyc,
RAG-1, myoglobin intron 2, Beta-fibrinogen intron 7) sequence data, employing
different taxon-sampling strategies. Based on the conclusions of these studies,
which are consistent with those of a forthcoming publication by R. Moyle et al.
using nuclear RAG-1 and RAG-2 data (which was partially presented at the AOU
meeting in 2004), it is clear that there are three distinct lineages of
(1) Formicarius and Chamaeza
(2) Grallaria, Myrmothera, Hylopezus, and Grallaricula
The affinities of these three groups are not yet well-established,
except for the strongly supported sister relationship between Pittasoma and
the genus Conopophaga, currently placed in its own monogeneric family
(Conopophagidae). Despite the lack of strong support for "deep"
relationships, a clade formed by any of the possible combinations of groups
(1), (2), and (3) to the exclusion of birds presently included in other
families has not been recovered in any analysis conducted so far.
Analysis: Taken together, these data strongly suggest that Formicariidae
is not monophyletic, and that it comprises three phylogenetically distinct
groups. Clearly, this calls for a change in classification at the family level
to be consistent with phylogenetic relationships.
Based on the results of the phylogenetic analyses, Irestedt et al.
(2002) proposed to limit membership in the Formicariidae only to Formicarius
and Chamaeza. I believe this is a sensible option. Rice (2005b)
presented a somewhat different alternative, in which he suggested that the
Formicariidae could include not only Formicarius and Chamaeza,
but also the tapaculos (Rhinocryptidae), as these two seemed to be sister
clades based on some molecular work. This is only a matter of taste, but it
seems to me that this would result in a highly heterogeneous family, although I
could easily be convinced that rhynocryptids are already quite heterogeneous to
begin with, and that Formicarius and Chamaeza do not really add
much variation. More importantly, however, I don't think this is the best
alternative because support for the ((Formicarius, Chamaeza),
Rhinocryptidae) arrangement is not strong. In fact, ongoing work based on c.
4000 bp of RAG sequence by Moyle et al. shows that Formicarius and Chamaeza
are sister to the Furnariidae (i.e. Furnariidae + Dendrocolaptidae) with strong
support, not to the Rhinocryptidae.
Irestedt et al. also proposed to erect a new family (Grallariidae)
for the clade formed by Grallaria, Myrmothera, Hylopezus, and Grallaricula.
I cannot think of a better alternative regarding the placement of these taxa.
In addition, we need to decide on what to do with Pittasoma.
There are two alternatives: one is to merge this genus with Conopophaga in
a single family (Conopophagidae), as advocated by Rice (2005b) and endorsed by
Krabbe and Schulenberg (2003, HBW). The other alternative would be to place Pittasoma
in a new monogeneric family, Pittasomidae (?). Considering the morphological
uniformity of the species of Conopophaga and how distinct these are from
Pittasoma (as evidenced by traditional, morphology-based taxonomy), at
first glance it would seem that the option of placing them in different
families represents the best possible course. However, Rice (2005a) presented
information on several different traits (morphology, natural history,
vocalizations) that support the close relationship between Pittasoma and
Conopophaga. Whether one wants to recognize one or two families is open
for discussion - all the traits discussed by Rice only help strengthen the
support for this clade by providing synapomorphies that complement the
mitochondrial and nuclear data, but do not resolve the issue of the taxonomic
rank that should be given to its two constituent lineages. An additional
argument that one could put forward in favor of Rice's proposal is that by
placing Pittasoma in Conopophagidae, we avoid introducing new family
names, which could be said to be conservative.
To summarize, there are five subproposals here:
circumscription of Formicariidae: Formicarius and Chamaeza
circumscription of Formicariidae: Formicarius, Chamaeza, and the
(d) place Pittasoma
Recommendation: (a) YES, (b) NO, (c) YES, (d) YES, (e) NO.
Literature Cited: See SACC website.
Cadena (in consultation with Nate Rice and Rob Moyle),
Comments from Robbins: "Cadena summarizes data from
various studies and presents (with input from Rice and Moyle) logical arguments
for all five subproposals. Thus, I vote as follows:
Comments from Stiles: "The question here is, are
the published data sufficient to justify the splits proposed? The Moyle et al.
data sound good but as they are unpublished, hence unreviewed (?), they should
not be taken as evidence at this point. As a general rule, I feel that the data
supporting arguments for taxonomic changes should at least be accepted for
publication -- is this the situation with this MS?); a manuscript only
submitted, or only a first draft, may suffer major changes before acceptance,
including incorporation of additional data and possible changes of some or all
“Aside from the Moyle et al. data, concordant results from two
independent studies using several genes plus morphology do appear sufficient to
justify splitting Formicariidae into at least two families: Formicariidae sensu
stricto (Formicarius, Chamaeza) and Grallariidae (Grallaria,
Grallaricula, Hylopezus, Myrmothera). The Pittasoma + Conopophaga clade
also seems well established, the main question being whether to put Pittasoma
in its own family or subsume it into Conopophagidae. If only because I find
tiny families unedifying if reasonable alternatives exist for combining them to
better indicate relationships, I favor transferring Pittasoma to the
Conopophagidae, at least for now. Hence, YES to all (a,b,c)
of the "sub-proposals").”
Comments from Zimmer: "YES. My votes on the
various options of this proposal are as follows: a) yes; b) no; c) yes; d) no;
“I think that restricting Formicariidae to Formicarius and Chamaeza makes
the most sense. Rhinocryptidae is so heterogeneous that its inclusion within
Formicariidae is not only uninformative, but it would obscure relationships.
Grallariidae seems like a natural grouping. The real dilemma is what to do with
Pittasoma. The evidence for its relationship with Conopophaga appears
strong, not only from a molecular standpoint, but also from a morphological and
vocal standpoint. The question is at what level do we treat the similarities
and differences between the two genera. In spite of certain similarities in
plumage pattern and some vocal characters, I'm more impressed by the
differences between the two groups. The difference in size and build is
obvious. The two species of Pittasoma average 96-110 g in weight. The
various gnateaters range from 20-28 g, except for the outsized melanogaster,
which is still only 36-43 g, less than half of the size of any Pittasoma.
The two species of Pittasoma lack the distinctive white or silvery
postocular tufts that characterize all but one (melanops) of the species
of Conopophaga. These postocular tufts are a conspicuous feature of the
gnateaters, and are used prominently in display and territorial interactions
with conspecifics. The tufts are arguably most developed and prominent in C.
melanogaster, which, in its size, more terrestrial habits, vocalizations,
and lowland Amazonian distribution, would otherwise seem to be the gnateater
that is a possible bridge to Pittasoma. Pittasoma does not
produce a mechanical wing-whirring sound, nor an accompanying chatter call,
both of which are prominent features of all Conopophaga species
except melanops. Both the wing-whirring and the chatter are regular
features of male-female chases in the gnateaters, and nothing similar is seen
in either species of Pittasoma. The two species of Pittasoma
both have songs that involve incredibly long series (often lasting minutes
rather than seconds) of well separated whistled notes (not linked together in a
rattle), and arresting alarm calls that recall squirrels (Sciurus) more
than birds. None of the gnateaters has a similar song, and only melanogaster
has calls that even remotely resemble those of Pittasoma. Ecologically,
the two groups are even more dissimilar, with Pittasoma being truly
terrestrial birds that regularly follow army ant swarms, whereas Conopophaga
are understory birds that descend to the ground but are not terrestrial, and
they rarely attend ant swarms. The two Pittasoma species and the various
gnateaters, treated separately, comprise two very distinct, and internally
cohesive, uniform groups. Combined, they become much more heterogeneous, from a
vocal, morphological, and ecological standpoint. The question becomes one of
whether we treat the differences at the generic or familial level. I would
favor treating them as being in separate families."
Comments from Jaramillo: "Great summary by Daniel of
various results recently published on this subject. I agree with the
recommendations, and do think that erecting a Pittasomidae seems unwarranted.
The expanded Conopophagidae just takes a bit of getting used to, but otherwise
it makes sense to me.
new circumscription of Formicariidae: Formicarius and Chamaeza
(b) NO- new
circumscription of Formicariidae: Formicarius, Chamaeza, and
accept family Grallariidae
place Pittasoma in Conopophagidae
(e) NO -
erect family Pittasomidae"
Comments from Stotz on 235e: "YES. I find
it hard to swallow Pittasoma and the gnateaters as a single family. They
constitute two very dissimilar groups (though not very species-rich). I think
we are better served by a separate family for Pittasoma."
Comments from Remsen: “(a) YES, (b) NO, (c) YES, (d)
YES, (e) NO. Note that if a separate
family were to be used for Pittasoma,
the correct name might be Pittasomatidae.
Bock’s (1994) monograph on group names cited Ridgway (1911) for this
family name, but I cannot find any mention of this in Ridgway (1911). Perhaps this would be a good candidate for
subfamily rank. There is one unremarked
character that Conopophaga shares
with Pittasoma, namely the tendency
for slightly scalloped markings on the back, which is unusual for the
antbird-tapaculo group in general.”