Table 1 Predicted drivers of speciation rates

From: Accelerated body size evolution in upland environments is correlated with recent speciation in South American freshwater fishes

General hypothesis

Mechanism of speciation

Variables

Predictions

References

Biotic

Rates of morphological evolution

Rates of body elongation evolution

High rates of morphological evolution of traits that are relevant for fish feeding ecology, physiology, and behavior can trigger speciation rates by enabling the exploration and partitioning of available resources

7, 11, 37

Rates of maximum body length evolution

Rates of oral gape position evolution

Rates of relative maxillary length evolution

Diversity-dependent speciation

Species diversity

Increasing diversity (e.g., stronger biotic interactions) results in greater specialization and faster speciation rates

9, 18

Abiotic

Climate-driven

Temperature

Warmer, wetter regions increase evolutionary speed, support more individuals, and hence higher speciation rates

5, 50

Surface runoff

Habitat-driven

Area

Larger areas, higher elevations, or greater structural habitat heterogeneity allow the coexistence of more species and enable higher isolation and allopatric speciation

6, 21

Elevation

Soil diversity

Stream gradient

  1. The table provides an overview of general hypotheses for the spatial variation in speciation rates, outlining the main mechanisms, variables used in our study, underlying predictions, and references.
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