title: Does the colonization of new biogeographic regions influence the diversification and accumulation of clade richness among the Corvides (Aves: Passeriformes)?
abstract: Regional variation in clade richness can be vast, reflecting differences in the dynamics of historical dispersal and diversification among lineages. Although it has been proposed that dispersal into new biogeographic regions may facilitate diversification, to date there has been limited assessment of the importance of this process in the generation, and maintenance, of broad-scale biodiversity gradients. To address this issue, we analytically derive biogeographic regions for a global radiation of passerine birds (the Corvides, c. 790 species) that are highly variable in the geographic and taxonomic distribution of species. Subsequently, we determine rates of historical dispersal between regions, the dynamics of diversification following regional colonization, and spatial variation in the distribution of species that differ in their rates of lineage diversification. The results of these analyses reveal spatiotemporal differences in the build-up of lineages across regions. The number of regions occupied and the rate of transition between regions both predict family richness well, indicating that the accumulation of high clade richness is associated with repeated expansion into new geographic areas. However, only the largest family (the Corvidae) had significantly heightened rates of both speciation and regional transition, implying that repeated regional colonization is not a general mechanism promoting lineage diversification among the Corvides.
authors.affiliation: Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Kennedy
authors.affiliation: Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Borregaard
authors.affiliation: Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark.|Department of Life Sciences, Imperial College London, Ascot SL5 7PY, United Kingdom.
authors.forename: Knud A
authors.initials: KA
authors.lastname: Jønsson
authors.affiliation: Department of Life Sciences, Imperial College London, Ascot SL5 7PY, United Kingdom.
authors.forename: Ben
authors.initials: B
authors.lastname: Holt
authors.affiliation: Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark.
authors.forename: Jon
authors.initials: J
authors.lastname: Fjeldså
authors.affiliation: Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark.|Department of Life Sciences, Imperial College London, Ascot SL5 7PY, United Kingdom.
authors.forename: Carsten
authors.initials: C
authors.lastname: Rahbek
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D049810:Genetic Speciation; D010802:Phylogeny; D020308:Songbirds / Q000145:classification / Q000235:genetics / Q000502:physiology*
keywords: Biogeographic regions; centers of diversification; dispersal; passerine birds; speciation