Distribution

The Old World warblers are extraordinarily widespread, occuring on every continent except South America and Antarctica. If the Polioptilinae are included, there are representatives of Sylviidae sensu latu in South America as well. Most of the sylviid diversity occurs in the African and Oriental faunal regions, with a less diverse, but widespread group of species in the Palearctic. Nearctic and Australian species represent recent invasions from Siberia and Southeast Asia, respectively.

The centers of distribution for some major sylviid genera are as follows. Sino-Himalayan Region: Bradypterus, Cettia, Phyllo-scopus, Seicercus, Prima-, Southeast Asia: Megalurus and allies, Or-thotomus; Temperate Asia (Palearctic): Locustella, Acrocephalus, Hippolais; Africa: Cisticola and allies; Mediterranean/Middle Eastern (Palearctic) region: Sylvia. Relatively little exchange has occurred between Northern (Palearctic) and Southern (Oriental and African) Hemisphere faunas in the Old World, perhaps due to the East/West orientation of major barriers, including the Sahara and Gobi deserts, the Himalayas, the Alps, the Atlas, Caucasus, and other mountain ranges, and historically, the Tethys sea, which separated Africa from what is now the Palearctic. Conversely, in the Americas, where the major barriers are oriented North to South, many Neotropical migrant families originated in South America, then spread north to the Nearctic. Voous (1977) is of the opinion that all Old World sylviids arose in either the Indo-African region or the Sino-Himalayan region. While these are areas where the largest radiations have taken place, it is not clear where the common ancestor of the modern Sylviidae arose.

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