Authors:
Mruzek, Joseph, Budnick, William, Larson, Chad, Luc, Dinh, Passy, Sophia
Abstract:
Aim: Niche and dispersal processes influence biodiversity, but their relative importance along latitude is unclear. We predicted that: i) niche processes would dominate at high latitudes due to increased climatic stress, consistent with the physiological tolerance hypothesis and the Dobzhansky-MacArthur hypothesis and ii) dispersal limitation would prevail at low latitudes due to narrower niches and smaller range sizes, as postulated by the dispersal-ecological specialization tradeoff hypothesis, the latitude-niche breadth hypothesis, and Rapop (...)
Aim: Niche and dispersal processes influence biodiversity, but their relative importance along latitude is unclear. We predicted that: i) niche processes would dominate at high latitudes due to increased climatic stress, consistent with the physiological tolerance hypothesis and the Dobzhansky-MacArthur hypothesis and ii) dispersal limitation would prevail at low latitudes due to narrower niches and smaller range sizes, as postulated by the dispersal-ecological specialization tradeoff hypothesis, the latitude-niche breadth hypothesis, and Rapoport’s rule. Location: Central United States Time Period: 1993-2019 Major taxa studied: Stream algae, insects, and fish Methods: We examined the relative effects of environment (climate and physicochemistry) vs. space on stream biodiversity in seven latitudinal zones, spanning 19 latitudinal degrees. In each zone, species richness (α-diversity) was analyzed with multiple regression and variance partitioning. Compositional dissimilarity (β-diversity) within zones was assessed with distance-based RDA and variance partitioning. Results: For α-diversity, latitudinal variability of niche and dispersal processes conformed to our predictions in all three groups, except for dispersal processes in insects. However, the drivers of β-diversity did not follow our predictions. The latitude-niche breadth hypothesis and Rapoport’s rule were weakly supported only in fish. Main Conclusions: The importance of niche and dispersal processes varied predictably along the latitudinal gradient only for α-diversity. However, the niche effects were driven mostly by physicochemistry, and the dispersal effects were not always linked with ecological specialization and range size. This suggests that climate-based biodiversity theories do not have particular relevance for the streams in our study. Niche processes had a greater impact than dispersal processes across species groups and diversity metrics, emphasizing the primary role of the environment.
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