Predicting spatial similarity of freshwater fish biodiversity

Abstract

A major issue in modern ecology is to understand how ecological complexity at broad scales is regulated by mechanisms operating at the organismic level. What specific underlying processes are essential for a macroecological pattern to emerge? Here, we analyze the analytical predictions of a general model suitable for describing the spatial biodiversity similarity in river ecosystems, and benchmark them against the empirical occurrence data of freshwater fish species collected in the Mississippi-Missouri river system. Encapsulating immigration, emigration, and stochastic noise, and without resorting to species abundance data, the model is able to reproduce the observed probability distribution of the Jaccard similarity index at any given distance. In addition to providing an excellent agreement with the empirical data, this approach accounts for heterogeneities of different subbasins, suggesting a strong dependence of biodiversity similarity on their respective climates. Strikingly, the model can also predict the actual probability distribution of the Jaccard similarity index for any distance when considering just a relatively small sample. The proposed framework supports the notion that simplified macroecological models are capable of predicting fundamental patterns-a theme at the heart of modern community ecology. macroecology ͉ river networks ͉ Jaccard index ͉ average annual runoff production ͉ Mississippi-Missouri basin T he fundamental mechanisms that underlie emergent biodiversity patterns are the fabric of the large canvas of ecological complexity (1-5), whose functioning across spatial and temporal scales is still challenging modern ecologists (6, 7).River ecosystems, like tropical forests, constitute an invaluable source of species diversity whose study can shed light on these puzzling issues (8), and whose insights will in turn resonate in the conservation biology of freshwater fauna suffering extinction rates comparable to the species decline in tropical rainforests (9). Riverine ecology has recognized the importance of geomorphology for biodiversity (10): on the one hand, ecologists have investigated the role of branches (11-13) and riparian zones (14) as primary habitats as well as the importance of tributaries (15) in sculpting species diversity (16, 17); on the other hand, theoretical studies have looked into possible implications of dendritic networks (18) on population persistence (19), species richness, and spatial turnover (20). Recent advances have also pointed out that simplifying neutral assumptions can reproduce important macroecological patterns in such dendritic structures (21).Indeed, despite the fact that biodiversity similarity among habitat patches is crucial to dispersal, speciation, and adaptation to climate diversity at large scales (22) and can also be related to species richness (23, 24), it is not well understood yet. Here, we develop an analytical model suggesting that essential features of biodiversity similarity in river ecosystems may be captured by using only the occurrence...

Between Geometry and Biology: The Problem of Universality of the Species-Area Relationship

“…C in Šizling et al 2009b for a detailed explanation). Unlike in the other two data sets, some examined plots were not adjacent in the bird survey, with gaps of up to 200 m. Longer interplot distances, however, should make the Jaccard index between those plots lower (due to distance decay in community similarity; e.g., Nekola and White 1999;Azaele et al 2009) and thus make z higher. Hence, the true z values for birds should be lower than those plotted, which further accentuates the differences between the z-D relationships of the three groups, making our test conservative.…”

Downscaling species occupancy from coarse spatial scales

“…This is even more striking when highlighting the gross simplifications that we assumed in the model: translational and rotational invariance that are generally violated in natural populations; smoothed geometry of the study region; temporal stationarity; and a simple form for the pair correlation function. Had we employed more general, yet realistic, functions (e.g., see Azaele et al 2009) for this latter, we would likely have obtained even more satisfactory results. Fig.…”

Spatial variation in branch size promotes metapopulation persistence in dendritic river networks

“…For example, studies on macroinvertebrate populations in New Zealand streams found that population structure was better explained by a combination of local and regional forces rather than by any scale-specific set of processes individually (Thompson & Townsend, 2006). Because high dispersal rates are often sufficient to swamp the effects of local population dynamics, other investigations found that fish community dynamics in the Mississippi-Missouri drainage could be modelled with only regional dispersal-driven processes (Azaele, Muneepeerakul, Maritan, Rinaldo, & Rodriguez-Iturbe, 2009;Convertino et al, 2009;Muneepeerakul et al, 2008). Because high dispersal rates are often sufficient to swamp the effects of local population dynamics, other investigations found that fish community dynamics in the Mississippi-Missouri drainage could be modelled with only regional dispersal-driven processes (Azaele, Muneepeerakul, Maritan, Rinaldo, & Rodriguez-Iturbe, 2009;Convertino et al, 2009;Muneepeerakul et al, 2008).…”