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Unformatted text preview: GUEST EDITORIAL Evolution of bird migration in a biogeographical context Bruno Bruderer 1 * and Volker Salewski 2 INTRODUCTION Most authors agree that migratory movements are a wide- spread and evolutionary old feature among animals, implying that birds must have inherited a broad set of capacities for migration from their ancestors (e.g. Berthold, 1999; Piersma et al. , 2005), and that discussing the evolution of bird migration does not entail an explanation of the ‘deep origin’ of migration itself, but is rather confined to the question of the expression of migratory capacities in certain lineages (Rappole et al. , 2003). Three questions, however, often complicate discussions on the evolution of bird migration: (1) whether migration evolved from the breeding grounds towards the wintering grounds or vice versa (e.g. Bell, 2000, 2005), a question which was often disguised and simplified in the discussion about a ‘southern-home theory’ (migration evolved in tropical low-latitude breeding areas, which are now the non- breeding areas of many long-distance migrants) vs. a ‘north- ern-home theory’ (migration evolved in present-day high- latitude breeding areas) (e.g. Gauthreaux, 1982; Rappole, 1995; Rappole & Jones, 2002); (2) whether long-distance migrants breeding in the Palaearctic must generally be supposed to have their phylogenetic origin in tropical habitats and/or at low latitudes (where many taxa currently have their highest diversity); and (3) whether evolution of migration is a feature of particular phylogenetic lineages or the result of independent adaptive changes. Salewski & Bruderer (2007) focused on the first of these questions, and concluded that bird migration evolved in populations that had dispersed (spread) into or found themselves living in increasingly seasonal breeding areas, where individuals with a strong genetic predisposition for migration had a selective advantage when moving towards less severe climates for the non-breeding period. A decisive point 1 Swiss Ornithological Institute, CH-6204 Sempach, Switzerland and 2 Max-Planck- Institut fu ¨r Ornithologie, Vogelwarte Radolfzell, Schlossallee 2, D-78315 Radolfzell, Germany *Correspondence: Bruno Bruderer, Swiss Ornithological Institute, CH-6204 Sempach, Switzerland. E-mail: firstname.lastname@example.org ABSTRACT We infer from the literature that migratory habits of birds evolved in various phylogenetic lineages and biogeographical contexts, either after gradual range expansion into seasonal habitats, or due to environmental changes within established breeding ranges. Shifts of breeding ranges are the results of interac- tions between colonization due to dispersal and extinction due to deteriorating conditions. Range expansions provide a platform for the evolution of migration from the newly colonized areas towards seasonally favourable non-breeding areas....
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