Abstract
AbstractAimTo define the major biogeographical regions and transition zones for freshwater fish species.TaxonStrictly freshwater species of actinopterygian fish (i.e. excluding marine and amphidromous fish families).MethodsWe based our bioregionalization on a global database of freshwater fish species occurrences in drainage basins, which, after filtering, includes 11,295 species in 2,581 basins. On the basis of this dataset, we generated a bipartite (basin‐species) network upon which we applied a hierarchical clustering algorithm (the Map Equation) to detect regions. We tested the robustness of regions with a sensitivity analysis. We identified transition zones between major regions with the participation coefficient, indicating the degree to which a basin has species from multiple regions.ResultsOur bioregionalization scheme showed two major supercontinental regions (Old World and New World, 50% species of the world and 99.96% endemics each). Nested within these two supercontinental regions lie six major regions (Nearctic, Neotropical, Palearctic, Ethiopian, Sino‐Oriental and Australian) with extremely high degrees of endemism (above 96% except for the Palearctic). Transition zones between regions were of limited extent compared to other groups of organisms. We identified numerous subregions with high diversity and endemism in tropical areas (e.g. Neotropical), and a few large subregions with low diversity and endemism at high latitudes (e.g. Palearctic).Main conclusionsOur results suggest that regions of freshwater fish species were shaped by events of vicariance and geodispersal which were similar to other groups, but with freshwater‐specific processes of isolation that led to extremely high degrees of endemism (far exceeding endemism rates of other continental vertebrates), specific boundary locations and limited extents of transition zones. The identified bioregions and transition zones of freshwater fish species reflect the strong isolation of freshwater fish faunas for the past 10–20 million years. The extremely high endemism and diversity of freshwater fish fauna raises many questions about the biogeographical consequences of current introductions and extinctions.
Highlights
For almost two centuries, biogeographers have classified continental areas of the world into distinct biogeographical regions on the basis of organism distributions across the Earth (Wallace, 1876; Cox, 2001; Holt et al, 2013)
Some studies explicitly defined transition zones as distinct regions (e.g., Holt et al, 2013), whereas others included transition zones in major regions (Kreft & Jetz, 2010). This question of transition zones was settled to some extent in the major synthesis of Morrone (2015), proposing that transition zones should not be considered as distinct regions, but rather as transitional boundaries between major regions
We found six major regions spatially nested within the two supercontinental regions (Figure 2b), that we named following Morrone (2015)
Summary
Biogeographers have classified continental areas of the world into distinct biogeographical regions on the basis of organism distributions across the Earth (Wallace, 1876; Cox, 2001; Holt et al, 2013). Multiple studies have tried to identify the major biogeographical regions for birds (Procheş & Ramdhani, 2012; Rueda, Rodríguez, & Hawkins, 2013; Holt et al, 2013), mammals (Kreft & Jetz, 2010; Procheş & Ramdhani, 2012; Rueda et al, 2013; Holt et al, 2013), amphibians (Procheş & Ramdhani, 2012; Rueda et al, 2013; Holt et al, 2013; Vilhena & Antonelli, 2015; Edler et al, 2016) and reptiles (Procheş & Ramdhani, 2012) The result of this upsurge was a debate on the precise limits of biogeographical regions. This synthetic model can be considered as a general framework to test for biogeographical regions
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
