Genetic study clarifies relationships between different subspecies of the Common Chiffchaff.
LBJ. Bird watchers will know what this abbreviation stands for: Little Brown Job. It refers to the large number of small brown passerines that are difficult to distinguish. A nice example of a LBJ is the “Chiffchaff complex”. This collection of small birds used to be considered one species, but detailed studies – based on genetics, acoustics and morphology – revealed the presence of four species: Common Chiffchaff (Phylloscopus collybita), Iberian Chiffchaff (P. ibericus), Mountain Chiffchaff (P. sindianus) and Canary Islands Chiffchaff (P. canariensis). In addition, these species can be divided into several subspecies. As the name already implied, the situation is quite complex. A recent study in the journal PLoS One tried to unravel the complicated relationships in this group of birds.
Marko Rakovic and his colleagues sampled across the range of the Chiffchaff complex, from western Europe to Siberia. Next, they sequenced two genes (the mitochondrial ND2 and the Z-linked ACO1I9). Analyses of these markers confirmed the delineation of the four recognized species.
However, some Z-linked alleles were shared between Common Chiffchaff and Canary Islands Chiffchaff. Moreover, based on the ND2-gene, one individual from the Canary Islands was located within the Common Chiffchaff group (see orange group in the figure below). Could it be that these species occasionally hybridize?
Let’s have a closer look at the patterns within these Common Chiffchaff. This species is generally divided into several subspecies:
Based on the mitochondrial ND2-gene, all these subspecies form distinct clades. However, this was not the case for the other genetic marker. Genetic variation is shared between the subspecies abientus and collybita, which are known to hybridize in Sweden (see for example Hansson et al. 2000). The data did not reveal hybridization between abientus and tristis, altough recently a hybrid zone was discovered in the Urals (see for example Shipilina et al. 2017 and this blog post).
Less is known about the southern subspecies of the Common Chiffchaff. The Anatolian Peninsula of Turkey houses brevirostris, while caucasicus breeds more to the east in Armenia. Finally, menzbieri is known from eastern Iran and the border with Turkmenistan. The genetic analyses clustered brevirostris and caucasicus. In the eastern part of their range, they might hybridize with menzbieri.
The researchers also sampled in a region that is normally not included in the distribution of the Common Chiffchaff: Mount Hermon (situated near the border between Lebanon and Syria). This population turned out to be a mix of brevirostris, caucasicus and colybita. Probably these birds use Mount Hermon as a wintering area. Interestingly, this population also contained alleles that were not present in any of the other subspecies. Perhaps this population might represent a yet unnamed taxon. Things just got a bit more complex again…
Rakovic, M., Neto, J.M., Lopes, R.J., Koblik, E.A., Fadeev, I.V., Lohman, Y.V., Aghayan, S.A., Boano, G., Pavia, M., Periman, Y., Kiat, Y., Ben Dov, A., Collinson, J.M., Voelker, G. & Drovetski, S.V. (2019) Geographic patterns of mtDNA and Z-linked sequence variation in the Common Chiffchaff and the ‘chiffchaff complex’. PLoS One 14(1):e0210268.
This paper has been added to the Phylloscopidae page.