Abstract
Abstract. Drainages reorganise in landscapes under diverse conditions and process dynamics that impact biotic distributions and evolution. We first investigated the relative control that Earth surface process parameters have on divide migration and stream capture in scenarios of base-level fall and heterogeneous uplift. A model built with the Landlab toolkit was run 51 200 times in sensitivity analyses that used globally observed values. Large-scale drainage reorganisation occurred only in the model runs within a limited combination of parameters and conditions. Uplift rate, rock erodibility, and the magnitude of perturbation (base-level fall or fault displacement) had the greatest influence on drainage reorganisation. The relative magnitudes of perturbation and topographic relief limited landscape susceptibility to reorganisation. Stream captures occurred more often when the channel head distance to divide was low. Stream topology set by initial conditions strongly affected capture occurrence when the imposed uplift was spatially heterogeneous. We also integrated simulations of geomorphic and biologic processes to investigate relationships among topographic relief, drainage reorganisation, and riverine species diversification in the two scenarios described above. We used a new Landlab component called SpeciesEvolver that models species at landscape scale following macroevolutionary process rules. More frequent stream capture and less frequent stream network disappearance due to divide migration increased speciation and decreased extinction, respectively, especially in the heterogeneous uplift scenario in which final species diversity was often greater than the base-level fall scenario. Under both scenarios, the landscape conditions that led to drainage reorganisation also controlled diversification. Across the model trials, the climatic or tectonic perturbation was more likely in low-relief landscapes to drive more extensive drainage reorganisation that in turn increased the diversity of riverine species lineages, especially for the species that evolved more rapidly. This model result supports recent research on natural systems that implicates drainage reorganisation as a mechanism of riverine species diversification in lowland basins. Future research applications of SpeciesEvolver software can incorporate complex climatic and tectonic forcings as they relate to macroevolution and surface processes, as well as region- and taxon-specific organisms based in rivers and those on continents at large.
Highlights
Topographic structure is primarily controlled by climate, tectonics, and lithological erodibility (Whipple, 2004; Anders et al, 2008; Han et al, 2015; Perron, 2017)
Drainages reorganise by divide migration, which is the progressive movement of a drainage divide, and stream capture that occurs when a portion of a stream network loses connectivity to its former network as it joins an adjacent network (Fig. 1; Bishop, 1995)
The “Video supplement” contains animations (V1–V3) of selected trials that exemplify the topographic response to the single base-level fall or fault throw perturbation of a trial
Summary
Topographic structure is primarily controlled by climate, tectonics, and lithological erodibility (Whipple, 2004; Anders et al, 2008; Han et al, 2015; Perron, 2017). Spatiotemporal variability in these controls can induce spatially variable erosion rates that can alter the planform topology of drainage networks and the longitudinal profiles of channels in regions with only metres to thousands of metres of relief (Gilbert, 1877; Giachetta et al, 2014; Forte et al, 2016; Willett et al, 2014; Whipple et al, 2017). Mechanistic models of biologic and geomorphic processes can provide information on complex process interactions, potentially guiding future empirical studies on the river capture hypothesis and other lines of inquiry on the intersection of landscapes and biodiversity
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