Neotropical Biodiversity: Hypotheses of Species Diversification and Dispersal in the Andean Mountain Forests
TThe tropical montane cloud forests of the Andes harbor an exceptional species diversity and endemism, which is currently under threat from rapid environmental change. Understanding the patterns and processes behind this diversity is a major challenge. In
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Neotropical Biodiversity: Hypotheses of Species Diversification and Dispersal in the Andean Mountain Forests Angela M. Mendoza-Henao and Juan C. Garcia-R
9.1 Introduction It is well established that species diversity is unevenly distributed across the globe (Wallace 1876) and a high proportion of it occurs in the tropics (Gaston 2000), particularly in the Andean mountain forests. The Andes hosts an exceptional diversity and endemism of vertebrate biota. More than 3400 vertebrate species (excluding fishes) are found in this mountain region and almost half of them are endemic (Myers et al. 2000; Orme et al. 2005; Elsen et al. 2018). The substantial number of species occurring in the Andes is a reflection of high beta diversity and spatial turnover at local and regional scales (Jankowski et al. 2009; Sklenář et al. 2014). However, this high biodiversity raises questions about the relevance of the different driving factors associated with species diversification and dispersal events. Several hypotheses have been suggested to help explain the high diversity in the Andes (Table 9.1). Species richness and endemism are attributed to a mixture of historical, evolutionary, and ecological processes (Rahbek and Graves 2001; Rahbek et al. 2007, 2019a; Fjeldså et al. 2012; Rangel et al. 2018). The processes alone are not mutually exclusive but instead form a complex dimensional interrelationship for the observed spatial and temporal patterns of species diversity in the Andes region. Thus, environmental heterogeneity, in both time and space, and evolutionary history, seems to be relevant for understanding the origin and distribution of extant biodiversity (Rull 2011; Antonelli et al. 2018; Perrigo et al. 2020). The mechanisms of diversification differ based on the relative role of each process and the A. M. Mendoza-Henao Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City, México J. C. Garcia-R (*) Molecular Epidemiology and Public Health Laboratory, Hopkirk Research Institute, School of Veterinary Science, Massey University, Palmerston North, New Zealand e-mail: [email protected] © Springer Nature Switzerland AG 2021 R. W. Myster (ed.), The Andean Cloud Forest, https://doi.org/10.1007/978-3-030-57344-7_9
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Table 9.1 Some of the hypotheses that explain the biodiversity in the Andes region Category Evolutionary
Spatial and ecological
Hypothesis Time-forspeciation (mountain museum hypothesis) Diversification rate (species pump)
Summary description References Earlier colonization of regions or habitats Stephens and Wiens (2003) facilitates higher richness because they have more time for in situ speciation and accumulation of species
Faster diversification rates (i.e., speciation minus extinction over time) of clades in some regions and habitats can generate higher species richness Pleistocene Pleistocene oscillations caused oscillations fragmentation of species ranges and local adaptation of populations Andean An
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