Split Common Gallinule (Gallinula
galeata) from Common Moorhen (G.
chloropus)
Proposal (416) to South
American Classification Committee
Effect on South American CL: this
proposal would split the New World Common Gallinule (Gallinula galeata) from the Old World Common Moorhen (G. chloropus).
Background: Gallinula chloropus is one of these
cosmopolitan species that shows only minor morphological differences over a
huge range. There has been little controversy regarding this arrangement, all
controversy seems to have been focused on the English name of this bird.
Plumage
differences between Old World and New World birds are slight, although bill
morphology differs. Old World forms have an elliptical shaped bill shield that
is rounded at top, whereas New World forms have a truncated topped shield that
is widest at the top.
New information: Recently Constantine et al. (2006) used
Gallinula chloropus as an example (p.
139) of how paying attention to sound may uncover biodiversity. They
illustrate the shield and head shape differences of American and European
birds, as well as the longer bill of New World gallinules. But they also
describe rather extreme differences in voice between the two populations,
publish sonograms and provide examples (on CD) of these differences. What
appears to be the primary vocalization in the New World population is a rich
nasal laughter, whereas the homologous call in the Old World populations is a
rather short, simple quavering note lasting less than
half a second kruuuk. A secondary call type with paired notes is similar in
note structure between the two populations, but not in tempo, in which
differences are apparent. These vocal differences can be heard on xeno-canto,
making sure to include examples from outside of the Americas, here is the link
that will do this for you:
Groenenberg
et al. (2008) recently published molecular data that addresses some species of Gallinula. They were interested in
unraveling the relationship of Gallinula
on two South Atlantic Islands (Gough and Tristan da Cunha), but also sampled
New World and Old World representatives of Gallinula
chloropus as well as Fulica. They
analyzed molecular data from the D-loop, tRNA-Lysine/ATP8 and cytochrome b.
Their result shows Gallinula chloropus
to be polyphyletic. They confirm that two separate taxa once inhabited Gough (G. comeri) and
Tristan da Cunha (G. nesiotis), and
this pair is sister to an Old World group of populations of G. chloropus. Their samples came from
Europe, Africa, and Asia. Two samples from the New World (Suriname) are basal
to the Old World and Atlantic Island clades. The paper is open access and
available here:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0001835
In several
Gallinula species plumage is
conservative, and much of the difference is in the shield shape and color, or
in body size. This is parallel to the situation in coots (Fulica). Gallinula chloropus,
G. nesiotis, and G. tenebrosa show
similar bill coloration of a yellow-tipped red bill with a red shield, although
shield shape and size differs. Gallinula
angulata is small and has much more extensive yellow on the bill than the
other three. Otherwise body plumages are similar, although angulata and chloropus
show the white flank stripe, whereas nesiotis
and tenebrosa do not. Leg color
varies among species. In essence the bill shape differences between Old World
and New World populations of G. chloropus,
as well as body size differences (OW birds are smaller), are small, but not
that different from currently accepted species within the group.
On the other
hand, the vocal differences between OW and NW Common Gallinules are quite extreme,
and it does not surprise me that OW populations are sister to the small and
flightless Tristan Moorhens, rather than to NW birds. If a wider sample of Gallinula had been looked at in the
molecular paper, it is quite possible that other OW Gallinula taxa (tenebrosa
and angulata) may also be closer to
OW G. chloropus than are the NW
birds.
Notes – Galapagos populations sound essentially
like mainland South American birds, and respond to playback from Eastern North
American birds (Jaramillo pers. obs.). Hawaiian populations are more distinct,
and need to be looked at in more detail, particularly with respect to voice. I
may have recordings but they are currently not accessible. But overall, they
are squarely in the NW population based on shield type. The very large and dark
highland (Titicaca Basin) form garmani
bears future attention too; again it is clearly a NW form.
Recommendation: I recommend a YES vote, to split Gallinula chloropus. The oldest name for
a New World population appears to be galeata
(Lichtenstein 1818).
I think we could keep using the English Name Common
Gallinule for Gallinula galeata, but
note that Constantine et al. (2006) suggest the English Name Laughing Moorhen
based on its distinctive voice as well as the name cachinnans (Laughing) for the widespread North American subspecies.
Literature Cited
Constantine, M. & The Sound Approach (2006). The
Sound Approach to Birding: A guide to understanding bird sound. Sound Approach,
Dorset.
2008 Ancient DNA Elucidates the Controversy about the
Flightless Island Hens (Gallinula sp.) of Tristan da Cunha. PLoS ONE 3(3):
e1835. doi:10.1371/journal.pone.0001835
Alvaro
Jaramillo, September 2009
Comments from Robbins: YES. Given that
I dont have access to the Constantine et al. CD, Im taking at face value that
the vocal differences that Alvaro points out on xeno-canto
are indeed analogous (there are no on line examples available on MLNS). Having said that, the few examples on xeno-canto demonstrate that Old and New World birds sound
nothing alike. Groenenberg et al. (2008) genetic data
support this split.
Comments from Stiles: YES, at
least tentatively. The genetic
data for a basal split between New and Old World Gallinula chloropus are convincing, with high bootstrap and
Bayesian support; the analysis of vocalizations by Constantine et al. also show
strong differentiation between these groups. The morphological differences are
not great, but would be in keeping with species-level distinctions in Gallinula and Fulica. Although
sampling from the New World was quite limited in the Gough-Tristan da Cunha
study, at least in my experience with birds from North, Central and South
America sound quite similar and nothing like the Old World birds. I note in passing that this would lay
to rest the burning English name controversy over whether to call our birds
gallinules or moorhens.
Comments from Zimmer: YES.
This is one of those groups where plumage characters are evolutionarily
conservative, and voice (plus frontal shield color/morphology) is a much better
indicator of relationship. And
yes, this would finally give us the perfect rationale for getting rid of
Common Moorhen as the English name for New World birds!
Comments from Remsen:
YES. All data point towards a
minimum of two species within chloropus.
Comments from Pacheco: YES. Os dados disponveis no momento apontam objetivamente para a interdependncia, ao menos, dos txons
presentes no Velho e no Novo Mundo.
Comments from Nores:
YES. La propuesta hecha por Alvaro es muy convincente ya que muestra que
existen diferencias en vocalizaciones (basado en Constantine et al. y
xeno-canto) y genticas (en Groenenberg et
al.). Como Gallinula
chloropus era un ejemplo siempre citado de especie cosmopolita, resulta un
poco desilusionante esta separacin, pero ya hay varios ejemplos similares
sobre la relacin de especies del nuevo mundo con las del viejo mundo. Por
ejemplo Larus maculipennis era considerada una subespecie de L. ridibundus, Larus dominicanus de L. marinus, Himantopus mexicanus de H. himantopus, Phoenicopterus chilensis de
P. ruber, Plegadis chihi de P.
falcinellus, etc. Otras especies,
por el contrario, tales como Sarkidiornis
melanotos, Nycticorax nycticorax, Chroicocephalus cirrocephalus, etc. se mantienen
y sera bueno ver tambin si
no son diferentes las del
Nuevo Mundo del las del
Viejo Mundo.