Proposal
(7) to South American Classification Committee
Combine New
World barbets and toucans into a single family, Ramphastidae, as in AOU (1998)
The monophyly of the New World
barbets and toucans is probably the most well verified clade in Aves! It has
been established by morphology (first proposed in my undergrad thesis in 1982!),
DNA hybridization by S&A, and several DNA studies by Lanyon and Co. I think
Lester Short was the only one to disagree with this issue, but he agreed with
the facts and suggested the be separate for classification. Further, all
studies including both Semnornis and Capito
or Eubucco have determined that New World barbets are paraphyletic- me
proposing the Semnornis is closer to toucans, and recently Barker and
Lanyon proposing that Capito and Eubucco are closer to toucans. Either way,
Capitonidae is paraphyletic. Basically,
there is no way to recognize Capitonidae with New World barbets alone
that does violate the well-established congruence among many independent
phylogenetic hypotheses. Now, given that South America does not include
any Old-World barbets, it is hard to know exactly what this
classification implies for them. One could be most historical by splitting them
into at least two new families. But the paraphyly of the new world
barbets would still make Capitonidae paraphyletic. In 1987 (in '82 in the thesis), I suggested
that all barbets and toucans be lumped into one family, which I
called Ramphastidae because the name is older than Capitonidae. Although strict
priority does not apply to family names, I did this to
prevent arbitrariness. Over the
years, I have sat on the side lines and seen this very reasonable
suggestion be ignored by most major classifications, field guide, and reference
works even though repeated studies have found that the toucans and barbets are
monophyletic, that the New World taxa are monophyletic, that the toucans are monophyletic,
but that NONE of the continental assemblages of barbets is monophyletic. Finally, the AOU in 1998 recognized a single Ramphastidae
including the barbets, but they still recognized a single Capitoninae, which
would ALSO be paraphyletic. So, I don't
know what you all think, but I think we should lump all barbets and toucans
into one family! At the very least, we are required to lump all the New World
barbets and toucans in this checklist into one family. I chose
Ramphastidae. Call it anything! But splitting them as suggested
here would be rejecting one of the single BEST supported, most agreed
upon results in avian systematics in recent decades! Let's compare that to recognizing the
Galbuliformes as separate from Piciformes. All though this split has been recognized, there
is far from agreement about it. Morphological phylogenetic papers have put
them within Piciformes (Cracraft, Raikow). Criticism of this by Olson was
completely unanalytical. Sibley and Ahlquist put them in outer space,
but didn't really conclude what they could be related to. So, this
situation is not universally accepted, has not been repeatedly supported. No
relationships for the Galbuliformes have been proposed, as far as I know, other
than in Piciformes or" we don’t know." I am all for progress, but we
don’t know isn't progress because only by showing that the group is closer to
something else than to Piciformes can you claim that the obvious
similarities they share in the hind limb are convergent and not due to shared
ancestry. So, I wouldn’t necessarily
vote against the recognition of Galbuliformes, but in comparison to the
toucan/barbet situation, this idea is half-baked and poorly supported. Of course, the earnest discussions have never
really started over this checklist's mission. Perhaps we will have votes for maintaining the
Capitonidae for the status quo. But that doesn't explain the non-traditional
Galbuliformes. I would LOVE to hear any
comments on these thoughts!
Rick Prum
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Remsen comments: ”Semnornis is the "problem"
taxon, right, so another possibility would be to create a third family for
that genus until the relationships among the 4 monophyletic groups
(assuming the two Semnornis are sisters) is resolved. (That's what
I recommended to H-M group). That way, 4 certain monophyletic lineages
would be given taxonomic recognition.
Prum comments: “Semnornis
is not the only problem taxon. The others are Trachyphonus- the ground barbets, and Caloramphus - the
little brown cooperative Asian barbets. Neither
Barker and Lanyon (Mol. Phil. Evol. 15:215-234) nor I found any support for
Sibley's two Old World Families. The problem is that Sibley didn't include
the problematic taxa Semnornis and Trachyphonus, nor the Asian Caloramphus,
which is very different from Megalaima and Psilopogon (the
members of Megalaimidae). Barker and Lanyon lacked the latter two. So, there is essentially no support for the
monophyly of any proposed concept of Lybiidae or Megalaimidae including Caloramphus. And the only critical tests come from my
work and Barker and Lanyon, and Lybiidae flunks both tests. There are no
agreed-upon clades within Old World barbets. So the solution presented here represents the
following notion: There are at least four families of barbets: Lybiidae, Megalaimidae
(including Caloramphus?), Capitonidae, Semnornithidae, Ramphastidae. There is no support for the monophyly of the
first two, and POSTIVE evidence in the only studies with enough
sampling that they are NOT monophyletic. The third family is ok. The
fourth is ok. It should be a separate
family given that it is either the sister group to Ramphastidae or the
sister group to Cap. + Ramph. (Barker and Lanyon). Given the volumes of data and analysis, I
would happily concede that Barker’s hypothesis is better supported than
mine. So, if you split up the barbets into multiple families, then you
need to recognize Semnornithidae. But,
why on earth would we want to recognize four families of barbets, two
of which have no support when a completely rational alternative option exists
that is congruent with all data? Will we soon recognize five families
of hummingbirds once we get a better idea of their phylogeny? Or 17 families of
tanagers? etc.? Believe me, I am all for
saving the Linnean system, which many phylogeneticists are abandoning or simply
ignoring. But to make it work we must make rational changes to the system to reflect
history. I think proliferation of subfamilies within a family is much more tolerable
than proliferation of uncertain families.
I say, we go with the AOU solution. -- note that AOU'98 used subfamily
taxa for all three lineages above. I
stand corrected! And about this, I am pleased to be wrong! -- (just to make
sure you know ... H&M does have Old World barbets in two separate families,
the Sibley familiesSee above. This alternative is NOT supported by any data,
and is contradicted by BOTH morphology and DNA sequence data. Thanks for more information!
Remsen comments: “A couple
of points concerning Rick's proposal: -- just for clarification ... the H-M classification
does not include any Old-World barbets within Capitonidae and recognizes its
sister relation to Ramphastidae. -- additional solutions to the "Semnornis
problem" that would maintain family rank for toucans and barbets: (1)
elevate the AOU’s Semnornithinae to family rank; (2) place Semnornis
as Incertae Sedis (as AOU does with a bunch of tyrannoid genera, largely
because of Rick’s studies, to avoid collapsing Tyrannidae, Pipridae, and
Cotingidae into 1 family). Is incertae
sedis something checklist's do when Rick Prum suggests a change? (This is
not a serious question!)
Comments from Prum: ”If we
collapse birds as "different" as New World barbets and toucans into 1
family (as does AOU '98), then it would be difficult to argue that Furnariidae +
Dendrocolaptidae should not also be merged into 1 family, as well as other
9-primaried oscine families. What birds
that are so different? What about the variation in size of falcons? Does anyone
doubt that the smallest Old World falcons are really falcons? Some of them
might even be genus Falco!? Do we
lose any information by expanding our concept of Ramphastidae by including
some small ones? And is Semnornis big
enough to be a toucan but Capito is not? What about Psilopogon? Looks
kind of toucan-like to me. The problem
is not whether the members of various family groups are variable, but
whether the groups are monophyletic. The question of ovenbirds and woodcreepers
is whether ovenbirds are monophyletic without woodcreepers, not whether they
are too different to be combined or too similar to be separated. Families are not
comparable levels of diversity. They are just clades with names
(hopefully). Some families are big and
some little. Some homogeneous and others variable. We should give up
making them parallel or consistent since they never can be. We should
just make them monophyletic. SO, I think we ought to mess with tradition
only enough to render it historically accurate.
Comments from Remsen: “Rick et
al. -- I'm not getting my point across. The monophyly of the Dendrocolaptidae
or Furnariidae is not an issue*. The reason I brought that up is that your (and
AOU '98's) broad Ramphastidae encompasses taxa that are less
"similar" by traditional, admittedly non-phylogenetic reasoning (as
evidenced by placement of barbets in separate family for a century or so), and
in my subjective opinion as well, than does the Dendro + Furn group. A century
of taxonomic ranking as separate families would suggest to most that the
difference between toucans and New world barbets is qualitatively different
than your example of small Falco from
large Falco. I don't think most of us think of barbets as just smaller
toucans. Given that ranking of
higher-level taxa is largely subjective and guided mostly by historical
momentum, I think it is worth considering two alternative solutions,
namely (1) three families (Capitonidae, Semnornithidae, Ramphastidae) or
(2) two plus Incertae Sedis status for Semnornis**... Looming ahead is the same
problem with the Schiffornis bunch -- leave them as Incertae Sedis or do away with
traditional family-level taxa Tyrannidae, Pipridae, and Cotingidae.
* I'm at home so can't check, but
other than one phenotypic character noted by Clench (with incomplete taxon
sampling), is there any evidence that the Dendros and Furnariidae are
monophyletic with respect to each other?
** Other than the distinctive bill
tip, is there any evidence that Semnornis itself is monophyletic?
Comments from Whitney: "I
agree with Rick, Mark, and probably about everyone else that we ought to leave
systematics alone unless well-corroborated evidence for monophyly dictates a
change. I also feel that "incertae sedis" is a useful place to put things
that represent problems, or about which there exists significant doubt for
whatever reason. This has two benefits: 1) it goes on hold rather than getting
lost somewhere at a higher taxonomic rank, and 2) it is probably more likely to
receive special attention, which is always good. I see no disadvantages to
calling something or even a small group of taxa "incertae sedis". Is
there a disadvantage I'm overlooking? C’mon, Rick, it's not all that many
taxa! Thus, I favor leaving "the
big ones" as Ramphastidae and” the little ones" as Capitonidae. We
all know what we are talking about, in part because that’s how we grew up,
in part because these are unambiguous phenotypic groups (with Semnornis the odd
one, "incertae sedis"). That said, and after reading the latest
rounds of correspondence, I am still unclear as to whether phylogenetic
analysis identified ANY break between these traditional assemblages or not. I'd
like to have that answered; sorry if I've missed it along the way. I would be
comfortable with Semnornis as ”incertae sedis" for now. And yes,
Van, let's wait to verify that Semnornis is indeed monophyletic (if that
piece of the puzzle is still missing). As
for Dendro and Furnar... if the tail is entirely rufous with powerful, sharp,
strongly curved, well-exposed spines, it's a woodcreeper. If not, it isn’t. I
don't think it needs to be any more complicated than that. One of these days,
genetic evidence should reveal the split that’s clearly there -- if indeed
it is recoverable from the organisms extant today
Comments from Stotz: "My
feeling on 7 is that I'm not sure what the best treatment is, but I feel like
putting everything in Ramphastidae sweeps remaining issues under the rug. Given
that the Old World Barbets are now usually split into multiple families, I
would think we could survive the same with the new world taxa.
Comments from Jaramillo: "I
vote NO on this one, mainly because the option of separating the Ramphastidae,
Capitonidae and Semnornithidae as Incertae Sedis is reasonable. I don't like
the idea of lumping all into Ramphastidae, it makes the family less meaningful,
information is lost in terms of understanding that a ramphastid is. I prefer
the option of expanding the families rather than lumping."