Proposal (416) to South American Classification Committee
Split
Common Gallinule (Gallinula galeata)
from Common Moorhen (G. chloropus)
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 (pg
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” while 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, where 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, while nesiotis
and tenebrosa do not. Leg color
varies between 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 don’t have access to the
Constantine et al. CD, I’m 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 disponíveis no momento
apontam objetivamente para a interdependência, ao menos, dos táxons 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
genéticas (en Groenenberg et al.). Como Gallinula
chloropus era un ejemplo siempre citado de especie cosmopolita, resulta un
poco desilusionante esta separación, pero ya hay varios ejemplos similares
sobre la relación 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 sería bueno ver
también si no son diferentes las del Nuevo Mundo de las del Viejo Mundo.”