Landscape evolution as a diversification driver in freshwater fishes.
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2022
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Resumo
The exceptional concentration of vertebrate diversity in continental freshwaters has
been termed the “freshwater fish paradox,” with > 15,000 fish species representing
more than 20% of all vertebrate species compressed into tiny fractions of the Earth’s
land surface area (<0.5%) or total aquatic habitat volume (<0.001%). This study asks
if the fish species richness of the world’s river basins is explainable in terms of river
captures using topographic metrics as proxies. The River Capture Hypothesis posits that
drainage-network rearrangements have accelerated biotic diversification through their
combined effects on dispersal, speciation, and extinction. Yet rates of river capture are
poorly constrained at the basin scale worldwide. Here we assess correlations between
fish species density (data for 14,953 obligate freshwater fish species) and basin-wide
metrics of landscape evolution (data for 3,119 river basins), including: topography
(elevation, average relief, slope, drainage area) and climate (average rainfall and air
temperature). We assess the results in the context of both static landscapes (e.g.,
species-area and habitat heterogeneity relationships) and transient landscapes (e.g.,
river capture, tectonic activity, landscape disequilibrium). We also relax assumptions
of functional neutrality of basins (tropical vs. extratropical, tectonically stable vs. active
terrains). We found a disproportionate number of freshwater species in large, lowland
river basins of tropical South America, Africa, and Southeast Asia, under predictable
conditions of large geographic area, tropical climate, low topographic relief, and high
habitat volume (i.e., high rainfall rates). However, our results show that these conditions
are only necessary, but not fully sufficient, to explain the basins with the highest
diversity. Basins with highest diversity are all located on tectonically stable regions,
places where river capture is predicted to be most conducive to the formation of
high fish species richness over evolutionary timescales. Our results are consistent
with predictions of several landscape evolution models, including the River Capture
Hypothesis, Mega Capture Hypothesis, and Intermediate Capture Rate Hypothesis,
and support conclusions of numerical modeling studies indicating landscape transience
as a mechanistic driver of net diversification in riverine and riparian organisms with
widespread continental distributions.
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Tropical biodiversity, River capture, Macroecology and macroevolution, Biogeography, Geobiology
Citação
VAL, P. F. de A. e. et al. Landscape evolution as a diversification driver in freshwater fishes. Frontiers in Ecology and Evolution, v. 9, jan. 2022. Disponível em: <https://www.frontiersin.org/articles/10.3389/fevo.2021.788328/full>. Acesso em: 29 abr. 2022.