Phylogeny and species limits in the Palaearctic chiffchaff Phylloscopus collybita complex: Mitochondrial genetic differentiation and bioacoustic evidence

Nucleotide sequences of the mitochondrial cytochrome b gene (1041 bp), analysis of vocalizations and behavioural evidence from zones of contact were used to reassess the species limits and phylogenetic relationships at the species and subspecies levels in the Phylloscopus collybita complex. A new classification is proposed which recognizes four biological species. Phylloscopus brehmii (Iberia) and P. canariensis (Canary Islands) are genetically and bioacoustically highly distinct. There is no mitochondrial gene now between them or with E. collybita. The Mountain Chiffchaff P. sindianus (with subspecies sindianus and lorenzii) is equally distinct genetically from southwest Asian subspecies of P. collybita (caucasicus, brevirostris). The status of the Siberian form tristis, which shares potentially synapomorphic characters with the Mountain Chiffchaff (ascending song notes, grey-brown adult plumage) but genetically closely resembles P. c. collybita and P. c. abietinus, remains uncertain, in two zones of secondary contact between taxa with ''greenish'' P. collybita) and brownish plumage, hybridization is either unrecorded (caucasicus v lorenzii, Caucasus Mountains) or its extent is insufficiently known (abietinus v tristis, west of Ural Mountains). A phylogeny reconstructed from nucleotide sequences agrees with one based on song and some morphological characters in identifying P. brehmii as the oldest branch within the chiffchaff group, Of the remaining taxa, four fall into a clade with greenish plumage (P. collybita ssp.), two into one with brownish plumage (P. s. sindianus, P. s. lorenzii), while the position of P. canariensis with respect to these two clades is uncertain. Molecular and phenotypic phylogenies contradict each other regarding the affinities of P.(ssp.?) tristis.