Abstract
AbstractAimAccelerating rates of anthropogenic introductions are leading to a dramatic restructuring of species distributions globally. However, the extent to which invasions alter the imprint of evolutionary history in species geographical ranges remains unclear. Here, we provide a global assessment of how the introduction, establishment and spread of alien species alters the phylogenetic signal in geographical range size using birds as a model system.LocationGlobal.Time periodContemporaneous.TaxaBirds.MethodsWe compare the phylogenetic signal in alien range size with that of native distributions of species globally (n = 9,993) and across different stages in the invasion pathway, from introduced (n = 965) to established species (n = 359). Using stochastic simulations, we test whether differences in phylogenetic signal arise from nonrandom patterns of species introduction, establishment or spread.ResultsGeographical range size in birds exhibits an intermediate phylogenetic signal, driven by the spatial clustering of closely related species. Nonrandom introductions, biased towards wide‐ranging species from particular clades and regions, produce an anomalously strong phylogenetic signal in the native range size of introduced species. In contrast, the phylogenetic signal in alien range size is substantially weaker than for native distributions. This weak phylogenetic signal cannot be explained by a lack of time for dispersal but is instead regulated by phylogenetic correlations across species in the location and number of introduction events.Main conclusionsWe demonstrate that the effects of anthropogenic introductions on the phylogenetic signal in range size vary across different stages in the invasion pathway. The process of transport and introduction amplifies the phylogenetic signal in the pool of potential invaders, whereas the subsequent pattern of spread decouples variation in alien range size from phylogenetic ancestry. Together, our findings suggest that evolutionary relatedness is likely to be a relatively weak predictor of the spread of invasive species.
Highlights
The geographical distributions of species are shaped both by the cur‐ rent environment and by their evolutionary history (Gaston, 2003)
The finding that phylogenetic signal in range size is stronger than expected under null models of speciation (Waldron, 2007) supports the controversial idea that geographical range size might be a heritable property of species, with important implications for understanding the past and future dynamics of biodiversity (Jablonski, 1987)
We found that the phylogenetic signal in the native range size of es‐ tablished species was highly consistent with that expected from a random sampling of introduced species [null model 3, expected λ = 0.43; Figure 3c; Table 2]
Summary
The geographical distributions of species are shaped both by the cur‐ rent environment and by their evolutionary history (Gaston, 2003). The size of the geographical range of species often exhibits a moderate but detectable phylogenetic signal, whereby range sizes are more similar amongst closely related species than amongst dis‐ tant relatives (Abellán & Ribera, 2011; Gaston, 1998; Hunt, Roy, & Jablonski, 2005; Machac, Zrzavý, & Storch, 2011; Webb & Gaston, 2005). The isolation of peripheral populations during speciation can result in daughter species initially having very different range sizes (Pigot, Phillimore, et al, 2010) This asymmetry is expected to diminish over time, either as species with small geographical ranges go extinct or as species expand their distributions to reach the limits imposed by the envi‐ ronment and their intrinsic traits (Waldron, 2007). The finding that phylogenetic signal in range size is stronger than expected under null models of speciation (Waldron, 2007) supports the controversial idea that geographical range size might be a heritable property of species, with important implications for understanding the past and future dynamics of biodiversity (Jablonski, 1987)
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