Proposal (635) to South American Classification Committee
Recognize
newly described Cyanocorax hafferi
Effect on South American CL: This proposal would
add a recently described species to our main list.
Background: Cohn-Haft, Santos, Fernandes and Ribas (2013)
recently described a new species of jay, Cyanocorax
hafferi (Campina Jay) from 8 specimens collected south of the rio Solimões
and west of the rio Madeira, with all but one known locality lying within the
Madeira-Purús interfluve, in the Brazilian state of Amazonas.
The new species is seemingly restricted
to the interface between Amazonian savannas (= campinas) and forest-edge, particularly the islands of low-stature
forest within campinas, and, as such,
could be considered a habitat specialist.
As stated by Cohn-Haft et al. (2013) in their diagnosis, the
new species “clearly belongs to the genus Cyanocorax
on the basis of its stiff frontal crest covering the nostrils (Ridgeway 1904)
and overall size and plumage similar to other members of the genus. The new species is the only member of the
genus with the following combination of characteristics: pale iris, pale-tipped
tail, three blue facial marks, and pale blue breast.
It is most similar to C. heilprini, from which it differs in
having a pale azure-blue versus dark purplish-blue wash to underparts and three
blue facial marks (supraocular, subocular, malar) versus one (malar). Dorsally, C.
heilprini and C. hafferi are more
similar, differing in the latter’s paler and duller-blue tone of the back,
wings, and tail. All other congeners
with pale eyes and white-tipped tail have a white breast (or yellowish-white
with no hint of blue) below the black bib.
All eight specimens were very similar
to one another genetically (< 0.3% divergence), and differed from their
nearest relatives, C. heilprini and C. affinis by approximately 0.7% and
1.8% sequence divergence respectively, in the mitochondrial genes ND2 and
cytochrome b.
Although they were able to document a
varied repertoire of vocalizations for the new species, the authors were unable
to confirm any vocal differences between it and C. heilprini. Furthermore,
the authors state that C. hafferi
responds with equal vigor to audio playback of C. heilprini vocalizations as they do to playback of their own
vocalizations. I assume that there has
been no opportunity by anyone to perform reciprocal playback experiments with
the only marginally better known and similarly range-restricted C. heilprini.
Analysis & Recommendation: There is no question
that C. hafferi represents a
previously unknown taxon. The only other
jay known to occur within the region occupied by C. hafferi is C. violaceus,
which differs substantially in plumage and vocalizations, and which is
restricted to várzea forest along the rio Purús. Genetic data show that the new species is
only slightly divergent from its closest relative, C. heilprini, which is further indicated by the vocal data. [As an
aside, I find it interesting that C.
hafferi is as close genetically as it is to the geographically distant
(trans-Andean) and ecologically very different C. affinis.] I have no field
experience with C. hafferi, but I
have listened to audio recordings, and their vocalizations were
indistinguishable to my ears from vocalizations of C. heilprini, a species that I have recorded in southern
Venezuela. This squares with the
conclusions of the authors that they were unable to identify any vocal
differences between the two species, as well as with the results of playback
experiments. The genetic data, taken
together with the vocal data and playback results, do suggest that C. hafferi and C. heilprini are somewhat tenuously divergent. However, the degree of differentiation in
plumage pattern and color saturation is consistent with that seen between some
other pairs of taxa within the genus that are considered to represent separate
species. That, combined with a pretty
substantial range disjunction that is greater than just the distance between
the closest seemingly appropriate enclaves of campina habitat on opposite banks of the rio Solimões/Amazon, would
seem to point to two taxa that are diverging and on independent evolutionary
trajectories.
In several respects, this case reminds
me of that involving the recently described Cinclodes
espinhacensis and whether or not it merited recognition as a species
distinct from Cinclodes pabsti: minimal genetic divergence; few (if any)
diagnostic vocal characters separating the two taxa; strong response of one
taxon to audio playback of the other in one-way trials; similar ecological
requirements; highly disjunct distributions.
In the case of the two cinclodes, I favored treatment as
subspecies. Something about the jay
situation feels a little different to me.
The extent of plumage differences between the two forms is greater,
involving pattern (presence/absence of supraocular and subocular marks) and
color (dorsally and ventrally), rather than just degree of color saturation (as
in the two cinclodes). Also, the nature
of the range disjunction is different.
The ranges of C. hafferi and C. heilprini are separated by two rivers
(the Solimões/Amazon and the Negro) that are both major biogeographic barriers,
and the range of C. heilprini does
not even extend to seemingly suitable campina
habitats close to the Amazon. It seems
pretty clear that the two are sister taxa that descended from a common ancestor
relatively recently. It also seems
pretty clear that the prospects for secondary contact are beyond poor.
In summation, I would recommend a YES
vote to recognize Cyanocorax hafferi
as a new species to our list. If
adopted, it should, following our conventions, occupy a position immediately
following C. heilprini in the linear
sequence. The English name of “Campina
Jay” chosen by the authors strikes me as entirely appropriate, highlighting, as
it does, the unique and threatened habitat to which the species is restricted.
Literature Cited:
Cohn-Haft,
M., M. A. Santos, Junior, A. M. Fernandes, and C. C. Ribas. 2013. A
new species of Cyanocorax jay from
savannas of the central Amazon. Pp. 306-310 in Handbook of the
Birds of the World. Special Volume: New Species and Global Index (del Hoyo et
al., eds.). Lynx Edicions, Barcelona.
Ridgway,
R. 1904.
The birds of North and Middle America, part 3. Bulletin U.S. National Museum, no. 50, pt. 3.
Kevin J. Zimmer,
July 2014
======================================================
Comments
from Pacheco:
“YES. In view of the arguments of Kevin,
my opinion that this relictual taxon should be treated at the species level.”
Comments from Stiles: “A very tentative YES… this is clearly a
borderline case, but given the geographical framework and the two major rivers
intervening, it seems reasonable to conclude that hafferi and heilprini are
on separate evolutionary trajectories and that contact is impossible in the
foreseeable future. The small genetic
distance between hafferi and the very
different affinis does suggest that
this is a case where genetics (at least the markers used) don´t tell us much
regarding speciation.”
Comments
from Remsen: “NO, with
great pain. The differences between hafferi and other members of the group
are, in my opinion, minor geographic variation.
The absence of any vocal differences is highly suspicious. Despite the strong geographic isolation, the
degree of genetic divergence is small and comparable to that typical between
taxa ranked as subspecies (although as you know I am opposed to using genetic
distance as a deal-maker or deal-breaker on taxon rank). Anyone who voted against Capito fitzpatricki or Cinclodes
espinhacensis as a species-level taxon should not vote for ranking hafferi as a species.”
Comments from Nores: “NO. The differences between hafferi and heilprini are
for me at the subspecies level. As Van
commented, despite the strong geographic isolation, the degree of genetic
divergence is small. Is also noticeable, the absence of any vocal differences.”
Comments
from Stotz: “NO This is
a tough one. The lack of vocal differences and limited genetic difference
make it hard to vote for this one, despite the big disjunction and plumage
characters. A lot of campinas
birds have some big range disjunctions accompanied by limited morphological
differentiation. What about north and south Amazonian Elaenia ruficeps, or Tachyphonus phoeniceus, Neopelma chrysocephalus, Euphonia plumbea and Cotinga cotinga in Peru. Not sure
what this means, but something about either recent dispersal or connection
within a subunit of these white sand species.”
Comments
from Jaramillo: “YES
– Borderline of course. I am going with Kevin’s suggestion; the issue of
recognition of song is a difficult one. Recognition of voices of closely
related taxa is expected, by default, and the informative situation is when
they do not respond to each other’s voices. The fact that they do respond to
the voice of a related species is not very informative at all particularly in oscines.”
Comments
from Areta: “A
very painful NO. As stated by others, this is clearly a borderline case and one
that makes us think on what a species is and how meaningful such distinction is
to understand biodiversity. Given this, I think a much more thorough work
should have been done to justify species status for hafferi. It is a difficult decision for anyone, and I am not
completely clear as to what would be the best choice. However, some key
elements inclined me toward a no vote.
“a) The authors mention the use, at
least occasionally, of terra firme forest
by hafferi, which together with the
very small genetic divergence indicate that birds tend to move around more than
what one would initially suspect. Given this fact, the 600km gap between hafferi and heilprini doesn't seem an insurmountable barrier to this jay
(indeed, 600km is about the SW-NE length of the geographic range of hafferi).
“b) The 0.3% genetic distance within hafferi in comparison to the 0.7%
distance between hafferi and heilprini seems to be easily accounted
for by the present day geographic distance between them. I imagine the same
genetic difference could be found between extremes in a population of jays
spanning the joint and continuous geographic range of hafferi+intervening gap+heilprini.
“c) Vocal differences between some Cyanocorax jays are not easy to notice,
let alone characterize. However, hafferi
and heilprini seem to be among the
least different in the genus, further complicating the recognition of hafferi as a valid species.
“d) The single qualitative
morphological difference that caught my attention were the three (hafferi) vs. one (heilprini) facial markings. Yet, its importance as a mating or
recognition cue is not clear and I am reluctant to recognize a different Cyanocorax species based on minor color
differences and slight differences in facial pattern.”
Comments from Cadena: “NO, though this
is a hard one. Others have noted that genetic distances are rather minor, but I
actually find them to be quite remarkable given that these birds are relatively
large-bodied, highly dispersive species from open areas, in which population
genetic differentiation is often rather shallow. That said, although this is
clearly a new taxon (phylospecies) and a spectacular finding, I am unconvinced
that the evidence is sufficient to treat it as a distinct biological species,
especially given the apparent lack of vocal differences. In other groups we
treat plumage variation of this sort as indicative of subspecific
differentiation. Kevin's point about range disjunction is well taken (I have
advocated for disjunctions of this sort as relevant in other cases, e.g. Arremon, Anthocephala), but given the
minor phenotypic differences, no vocal differences, and results of playback
trials, I think that hafferi is best
considered a subspecies of heilprini.”
Response from Mario
Cohn-Haft:
“Please know, everyone,
that I have no personal or even strong professional reaction to this
decision. I write now, not to defend any particular conclusion (either of
which -- species/subspecies -- seems reasonable to me), but rather to call
attention to what seem to me to be the key arguments in the decision and to try
to understand what sort of evidence would be needed to make a stronger
conclusion. The overall impression I got from reading the discussion of
the case was of a severely arbitrary process (which I suspect is unavoidable),
in which the criteria for decision-making remain vague or inexplicit (which IS
avoidable). I sort of wish I'd treated the question of taxonomic status
directly in the description (one of the reviewers even suggested subspecies
status), but I suspect it wouldn't make much difference, and it certainly was
easier to finish the manuscript on time without going into that.
“So,
here's my take on what I just read on the SACC site:
“Four
members voted YES for species, 5 voted NO, and one member did not vote.
Everyone who expressed an opinion about the validity of the taxon agreed that
it deserves a name, regardless of level.
“I
won't make much out of the order of the votes, since I'm not sure it's shown
accurately on the site, except to point out that the proposal was a YES and the
first votes (in the order listed on the site) agreed with the proposal; the
first NO vote seemed to release a flurry of NOs, suggesting (also quite
understandably) an aspect of peer pressure or self consciousness in the
process.
“Relevant
criteria:
“Genetic divergence.
Some
members mentioned that they don't like hard genetic distance cutoffs to serve
as taxonomic level criteria. However, it seems to me fairly obvious that
a larger difference (more like that found between other Cyanocorax spp.
pairs) would have made a YES vote more comfortable. One member felt the
differences to be remarkably large considering other ecological aspects (!),
but did not follow up on the significance of that.
“The
question I pose is "What does a relatively small genetic difference
mean?" One possible answer, and the one I expect is correct, is that
the two phenotypically and geographically distinct populations (taxa) have been
genetically isolated for a relatively short time. Does that make them
more or less likely to be distinct species? That's a valid question that
was not tackled directly by the members' arguments, but would seem to be
crucial to the debate. Perhaps it would be useful for SACC to have an
explicit stance or policy with respect to this subject.
“I
note here that, although the phylogenetic relationships between C. hafferi,
heilprini, and affinis were unresolved in the tree presented,
nevertheless hafferi differed in DNA sequence of the genes analyzed much
less from heilprini than from affinis. What does that
mean? What sort of situations lead to unresolved polytomies in the face
of strong differences in genetic distance? Is this biological or
methodological? What sort of new evidence could help resolve the
question? Answers to these questions might point to a clear solution to
the dilemma or at least make explicit what new analyses might shed light.
“Lack of vocal distinction.
“This
clearly was very important to almost everyone. Yet one member pointed out
that lack of vocal distinction seems to be widespread in the genus and
reciprocal response to playback is common in birds with similar voices,
regardless of species status; thus, lack of response is stronger evidence of
species distinctiveness than positive response is evidence of conspecificity.
“I'd
like to add a couple of observations here:
“1)
absence of difference is much harder to prove than presence of difference, so
stating no differences were found is not the same as stating there are none
(especially in birds with big intraspecific repertoires that are hard to
describe);
“2)
the vocal differences between hafferi and the other close spp. besides heilprini
were not carefully addressed in the original description, so it's possible that
there are few if any vocal differences among ANY of these species in the larger
clade;
“3)
having a "yardstick" for the relevance of this trait (voice) in the
genus would make the decision less arbitrary; for example, do cyanopogon
and chrysops differ vocally?
“4)
it's not unusual for sister or closely related species not to differ vocally;
for example, apparent lack of vocal distinction among Selenidera spp.
(except piperivora) or Rhegmatorhina or Gymnopithys spp.
doesn't seem to bother anyone.
“I
recognize that by addressing 1-3 above directly in the published description I
might have made the decision easier for you. However, point 4 to me is
the clincher that lack of vocal distinction is not an important character in
this discussion, in the case of jays specifically, and perhaps with most South
American birds in general. This was also stated more or less explicitly
by one of the members.
"Minor" morphological differences.
“This
is an important argument, I think, that was really not tackled head on.
It's entirely arbitrary to call differences minor or major, without some kind
of measure, be it a comparative one (inter- vs. intraspecific yardstick) or a
functional one (e.g., face patterns matter in mate choice, but overall color
doesn't) or a combination of those. Interestingly, the SACC proposal
suggests that the plumage differences are equivalent to or greater than those
found in other species in the genus. However, other members imply that
the differences are too small for species distinction and equivalent to
subspecies differences. But nobody is explicit about which taxa are informing
these personal yardsticks.
“I
suspect both the plumage differences (overall color and face pattern) between hafferi
and heilprini are important. But less subjective than that, I
believe that their intrapopulational uniformity points to good gene flow within
taxon, lack of geographic distance effects within, and lack of gene flow
between taxa. So, without dwelling on whether the differences are minor
or major, the pattern they show jibes with the DNA story: recently split
populations without evidence of gene flow between them. Does that make
them biological species? I sure don't know.
“Geographic distance and isolation.
“Hmm,
this is a real juicy one that nobody seems to know what to make of! The
apparent long distance and presence of well-known important biogeographic
barriers between the two taxa help people to consider treating them as distinct
species. Why? That would appear to be an argument about the chances
of their coming into contact any time soon, suggesting they'll continue to have
time to accumulate fixed differences between them that will prevent them from
interbreeding, i.e., that they'll keep speciating until such a time when they
might come into contact eventually. So, I think that's a guess about the
future.
“If
they were separated only by one big river and found immediately on opposite
banks, as is so often the case with distinct Amazonian sister taxa, the logical
extension of the argument in the paragraph above would be that these only-river
separated taxa have a greater chance of eventual future contact and that their
only subtle differences are likely to be tested with regard to their efficacy
as reproductive isolating mechanisms in the near future. Thus,
presumably, committee members would have less confidence in the taxons'
specific distinction. On the other hand, if they're found that close to
one another now and don't show signs of gene flow, then it could be argued that
they've already passed the test--they could interbreed, but don't. In
other words, the current spatial pattern doesn't make predictions about the
future, but rather tells the story of their past.
“Seems
a little wishy-washy to have it both ways. Does some sort of affirmation
about dispersal ability make a difference in this story? If the two were
on oceanic islands separated by open sea of the same distance, what would
committee members think? How does having a permeable matrix between them
(terra firme forest) and even patches of suitable habitat (campinas
here and there), apparently uninhabited, affect the decision? This would
appear to be another area where a clear expression on the part of the committee
would help everyone understand what the expected relationship is between
pattern and process and taxonomic rank.
“So,
to wrap up, I think perhaps some more explicit arguments in the description, if
they'd been made, might have helped members decide. However, I also think
that a clear expression by SACC members of what new evidence would help them
decide and how each kind of evidence would influence the decision would be
helpful, not only to me (or anyone else tempted to try to gather more
information relevant to taxonomic status), but also to fellow committee members
in an attempt to generate a consensus about what's a species and what's a
subspecies.
“I'm
inclined to describe the situation as one in which a widespread, western
Amazonian, campina-specialist jay fairly recently split into 2
allopatric populations that show consistent plumage differences, signs of good
dispersal ability, but a lack of occupation of all currently available habitat,
and little or no vocal differences (in birds that don't show much vocal
differentiation anyway). I suggest that the lack of vocal difference
means nothing (except lack of time for drift and lack of selective pressure for
differentiation in allopatry or even strong stabilizing selection on a big
repertoire with lots of communicable information content), but that the
morphological and genetic differences do mean something. But what?
Are they distinct species? How to tell?
“If
this is a timeless and solutionless issue and nobody's up for answering, then
I'll be happy to throw up my hands too, but also inclined to conclude that
every committee is just as arbitrary as ever and the conclusions don't really mean
much. But if there are some consistent answers, either with respect to
what more info committee members want to know about the case and how this would
affect the answer, or with respect to a new consensus based on further
contemplation of the subject by the committee, then I'll be real eager to hear.
“I
understand that everybody has tons of other stuff to do and that, even within
the context of SACC activities, this is just one case in zillions. I also
don’t mean to be smug or ungrateful for all the work you do and for making it
public. On the contrary, I found myself stimulated by this to try to
understand the process better and to try to stimulate you all to be a little
more explicit. Maybe it's already written down somewhere and I'm just
being dense. But if by chance anybody finds this to be a worthy nudge to
discuss the big issues more, then I'll be very pleased. Thanks!”