The combined effects of competition and niches on competitive outcomes of a phytoplankton model in heterogeneous acidified lakes

Summary

Competition and niche dynamics are critical for predicting species distributions under future acidification conditions. In this study, we develop a deterministic Lotka–Volterra competition model along a gradient using a trait-based approach. By analyzing the combined effects of competition and niche width on the competitive outcomes of aquatic organisms in heterogeneous acidified lakes, our theoretical analysis and numerical simulations yield new insights. We find a tradeoff between competition strength and niche width that facilitates transitions among competitive outcomes, including competitive exclusion, coexistence, and priority effects (bistability). In the absence of dispersal, as levels in habitats decrease, distinct transitions in competitive outcomes emerge for competing species with both similar and different niche widths. In the presence of dispersal, we identify two critical curves of niche breadth, which determine whether coexistence or priority effects occur. Generally, species with wider niches are likely to outcompete those with narrower niches. Additionally, inferior competitors with high dispersal rates are more likely to coexist with superior competitors that have lower dispersal rates, suggesting that higher diffusivity can compensate for both weak competition strength and narrow niches. This model provides valuable insights into how niche dynamics and competitive abilities influence competitive outcomes in heterogeneous acidified lakes.