Topographic controls on divide migration, stream capture, and diversification in riverine life

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.

Modeling the Evolution of Aquatic Organisms in Dynamic River Basins

“…Although our model of vicariant speciation is an extreme scenario in the sense that all species living in the captured portion of a river network undergo speciation instantaneously, it is less extreme than other proposed models. For example, in SEAMLESS (Albert et al, 2017) and SpeciesEvolver (Lyons et al, 2019), vicariance is the only mechanism for speciation, whereas our model includes a stochastic mode of speciation that is independent of geologic processes.…”

“…If the timescales of the two processes (vicariant and within‐stream speciation) were more similar, the effects of river capture would be muted. Indeed, Lyons et al (2019) show that a longer “wait time” for vicariant speciation to occur after a river capture reduces the effect of river network reorganization on species richness. Nonetheless, it is reasonable to expect that river capture could cause the speciation rate to be faster than the “background” speciation rate.…”

Drainage Reorganization Across the Puna Plateau Margin (NW Argentina): Implications for the Preservation of Orogenic Plateaus

“…The direction and magnitude of drainage reorganization is largely set by base level differences and perturbations across a drainage divide (e.g., Lyons et al, 2020;Mather, 2000;Robl et al, 2017). Divides migrate away from lower base levels until they reach a position with approximately equal slopes on each flank of a range (Ellis & Densmore, 2006).…”

“…This drainage reorganization can reintegrate internally drained plateau rivers and basins into the external drainage network; the subsequent base level lowering triggers rapid fluvial incision of plateau basins, dissecting and destroying characteristic low relief plateau morphology (e.g., Craddock et al, 2010;Heidarzadeh et al, 2017;House et al, 2008). Conversely, if drainage reorganization across a plateau margin is negligible, whether due to insufficient base level perturbations or conditions that impede erosion (e.g., aridity, resistant bedrock; Lyons et al, 2020), this may result in long-lived internal drainage and a preservation of low relief plateau morphology.…”

Dynamic Divide Migration as a Response to Asymmetric Uplift: An Example from the Zhongtiao Shan, North China

“…In recent years, there has been increasing awareness that divide is a kind of dynamic, rather than static, feature in geomorphic systems [2,[4][5][6][7]. Divide migration would change regional drainage area, sediment flux, and stream power, and hence influence regional erosion process, population genetic structure, and further present opportunities to examine landscape-scale interactions among tectonics, erosion, and ecology [2,[8][9][10][11][12][13]. Therefore, researches on divide mobility, subsequent fluvial network configuration, and the corresponding landscape evolution have been widely considered in recent years [2,4,6,[14][15][16][17].…”