Subspecies
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Synonyms
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Acanthis cannabina
Linaris cannabina
Carduelis cannabina
Note on the generic placement of this and other species formerly placed
in Carduelis, Serinus and related genera: these species pose a difficult
problem for songbird phylogeny and taxonomy. A large number of attempts
have been made to erect a natural system for these species: until
recently most authors had agreed on a system where the majority of
species were divided between the two genera Serinus and Carduelis.
Molecular studies, however, showed that the relationships within this
Serinus-Carduelis clade are much more complicated than previously
thought. Unfortunately, different molecular analyses do not agree on a
common phylogeny, thus leaving the nomenclature of the group unresolved.
Recently, Zuccon et al. 2012
have performed a phylogenetic analysis using both mitochondrial and
nuclear genetic markers. Although the phylogenies resulting from the two
datasets are not congruent, these authors recommend a new
classification of this group of birds, because their analyses show that
neither Serinus nor Carduelis in the current sense are monophyletic.
In principle, there are two options if one discovers that two or more
groups are mutually para/polyphyletic: (1) further split the groups
until only monophyletic groups remain, or (2) merge the groups and see
if the result is monophyletic. Zuccon et al. 2012
have chosen the first alternative and have resurrected a number of
rarely used genus names and have even described a new genus
(Agraphospiza). However, I think that this action is premature and will
therefore not provide taxonomic stability. As already noted by Sangster et al. 2011,
all current phylogenies of this group of birds suffer from the same
problems: (1) incomplete taxon sampling, (2) conflicting results, and
(3) low support of some clades. These authors recommend to wait with
nomenclatural changes until a more complete understanding of the
phylogeny of this bird assemblage is available.
I agree with Zuccon et al. 2012 that Serinus and Carduelis are not monophyletic if both are accepted as valid genera. However, I also agree with Sangster et al. 2011
that all current phylogenies of this bird group do not yet provide
conclusive evidence for their relationships. Most studies appear to
agree that the greenfinches are a monophyletic basal group. This could
support a splitting of the greenfinches from the rest of the species in
their own genus Chloris (see Sangster et al. 2011).
However, I think no groups should be separated from the rest of the
assemblage before the relationships of the remaining groups are clear. I
therefore combine all species in a single genus Carduelis (this name is
the oldest available name in the group). From a traditional perspective
this is not problematic, because the "lumping" of all species into
Carduelis creates a monophyletic group, albeit a very speciose one.
However, according to the results of Zuccon et al. 2012,
the lumping of all species into Carduelis is problematic, because in
their phylogeny the crossbills (genus Loxia) are nested within the
"Serinus-Carduelis" clade. Based on morphological data the crossbills
are clearly not members of the "Serinus-Carduelis" clade. The result of
Zuccon et al. is therefore surprising; it might in fact be caused by an
artefactual placement of the genus Loxia. This genus is placed very
differently in the mitochondrial DNA and the nuclear DNA analysis,
indicating that there is conflicting phylogenetic signal in both
datasets. On a morphological basis Loxia should be placed as a sister
group of the species Pinicola enucleator, that shares the apomorphic
traits (1) hooked (but not crossed) bill and (2) sexual color dimorphism
(red males, green females). Thus, in the tree of Zuccon et al. 2012
Loxia should be placed as a sister group of Pinicola enucleator, close
to the genus Pyrrhula. Therefore, I propose that the placement of Loxia
within the "Serinus-Carduelis" clade is an artefact and I recommend that
all (true) species of this clade should be placed in a large genus
Carduelis sensu lato until a more comprehensive understanding of the
relationships within this clade is available. In consequence, I place
the present species in Carduelis.
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Identification
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Distribution
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Biology
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