Taxonomy and phylogeny of reed warblers (genus Acrocephalus) based on mtDNA sequences and morphology

The mitochondrial cytochrome b gene of the majority ofAcrocephalus species (76 individuals) was amplified by PCR and sequenced directly. Nucleotide sequences (1068 base pairs) were used to reconstruct phylogenetic relationships within the genusAcrocephalus as well as betweenAcrocephalus and other sylviid warblers, particularlyHippolais. Acrocephalus andHippolais share ancestry and cluster in a monophyletic clade.Hippolais appears to represent a polyphyletic assemblage sinceH. icterina figures as the sister taxon toAcrocephalus, whereas “Hippolais”pallida andcaligata cluster withinAcrocephalus. The followingAcrocephalus clades could be recognized: (1) Large reed warblers form a clade consisting of a monophyletic Palearctic-Australasian subgroup (arundinaceus, stentoreus brunnescens, orientalis, australis, andvaughani) and a monophyletic Afrotropical subgroup (brevipennis, rufescens, gracilirostris, sechellensis, andnewtoni).A. griseldis holds an isolated position at the base of the large reed warbler clade. Within the small reed warblers, two probably monophyletic clades are apparent: (2) the striped species (withbistrigiceps, melanopogon, paludicola, andschoenobaenus), and (3) the small plain-coloured complex (consisting ofdumetorum, palustris, scirpaceus, s. fuscus, baeticatus, andavicenniae plus the neighbouringagricola-complex withagricola, tangorum, andconcinens). The relationship between these groups cannot be resolved. The molecular data clarify the status of some taxa, the systematic position of which has been controversial. A morphometric analysis (PCA) of 20 external characters confirmed the basic complexes, and unveiled adaptations of general importance among clades. At species level, we found less congruence between molecular and morphological data, which can be interpreted as a consequence of specializing adaptations and convergence. The major complexes established by molecular and morphometric analyses are further supported by distributional, acoustical, and oological affinities. A sound phylogenetic framework of the genus makes it now possible to examine the distribution of ecological and behavioural characters and to differentiate informative or convergent characters.Acrocephalus may be split into four previously recognized genera with the following names:Acrocephalus for the large,Calamodus for the striped,Notiocichla for the small plain, andIduna for the brownish “Hippolais” species.