Highly variable species distribution models in a subarctic stream metacommunity: Patterns, mechanisms and implications

Abstract

Metacommunity theory focuses on assembly patterns in ecological communities, originally exemplified through four different, yet non‐exclusive, perspectives: patch dynamics, species sorting, source‐sink dynamics, and neutral theory. More recently, three exclusive components have been proposed to describe a different metacommunity framework: habitat heterogeneity, species equivalence, and dispersal. Here, we aim at evaluating the insect metacommunity of a subarctic stream network under these two different frameworks. We first modelled the presence/absence of 47 stream insects in northernmost Finland, using binomial generalised linear models (GLMs). The deviance explained by pure local environmental (E), spatial (S), and climatic variables (C) was then analysed across species using beta regression. In this comparative analysis, site occupancy, as well as taxonomic and biological trait vectors obtained from principal coordinate analysis, were used as predictor variables. Single‐species distributions were better explained by in‐stream environmental and spatial factors than by climatic forcing, but in a highly variable fashion. This variability was difficult to relate to the taxonomic relatedness among species or their biological trait similarity. Site occupancy, however, was related to model performance of the binomial GLMs based on spatial effects: as populations are likely to be better connected for common species due to their near ubiquity, spatial factors may also explain better their distributions. According to the classical four‐perspective framework, the observation of both environmental and spatial effects suggests a role for either mass effects or species sorting constrained by dispersal limitation, or both. Taxonomic and biological traits, including the different dispersal capability of species, were scarcely important, which undermines the patch dynamics perspective, based on differences in dispersal ability between species. The highly variable performance of models makes the reliance on an entirely neutral framework unrealistic as well. According to the three‐component framework, our results suggest that the stream insect metacommunity is shaped by the effect of habitat heterogeneity (supporting both species‐sorting and mass effects), rather than species equivalence or dispersal limitation. While the relative importance of the source‐sink dynamics perspective or the species‐sorting paradigm cannot be deciphered with the data at our disposal, we can conclude that habitat heterogeneity is an important driver shaping species distributions and insect assemblages in subarctic stream metacommunities. These results exemplify that the use of the three‐component metacommunity framework may be more useful than the classical four perspective paradigm in analysing metacommunities. Our findings also provide support for conservation strategies based on the preservation of heterogeneous habitats in a metacommunity context.

The River Continuum Concept: lessons from the past and perspectives for the future

“…An abundance of work in stream metacommunity ecology is currently being done, demonstrated by the recent Freshwater Biology special issue "Metacommunities in river networks: The importance of network structure and connectivity on patters and processes" (2018). In general, the RCC supports a species-sorting paradigm of stream macroinvertebrate community structuring, due to the dominance of environmental heterogeneity, in the form of POM and light availability and in structuring local communities (de Mendoza et al 2017). Yet, how this varies over taxonomic groups and diverse stream conditions, influencing dispersal capability, remains an active area of study (Göthe et al 2017).…”

Seasonal shifts in the assembly dynamics of benthic macroinvertebrate and diatom communities in a subtropical river

“…By comparison, benthic macroinvertebrates, the main consumers in lotic ecosystems, comprise diverse species groups with different life cycles, functional roles, and trophic traits (Göthe, Angeler, Sandin, & Rasmussen, 2013). Temporal variation in community patterns is mainly caused by variation in a myriad of species life history features (Johnson, Carreiro, Jin, & Jack, 2012), while species interactions only play a relatively weak role among lotic macroinvertebrates (de Mendoza et al, 2018). Therefore, the community assembly mechanisms of lotic benthic macroinvertebrates and diatoms may be different due to the difference in their responses to seasonal changes in physio-chemical conditions and intensity of interspecific interactions.…”

Metacommunities in river networks: The importance of network structure and connectivity on patterns and processes

“…The eleven papers in this issue span a variety of approaches, including field (Brown, Wahl, & Swan, ) and laboratory experiments (Altermatt & Fronhofer, ), modelling (Anderson, Hayes, & Sarhad, ; Carraro, Mari, Gatto, Rinaldo, & Bertuzzo, ; Helton, Hall, & Bertuzzo, ; Valente‐Neto, Duraes, Siqueira, & Roque, ), species distribution models (de Mendoza et al., ), population genetics (Prunier, Dubut, Loot, Tudesque, & Blanchet, ) and conceptual synthesis (Tonkin et al., ). These studies cover a wide range of topics and focal organisms, including disease spread (Carraro et al., ), nutrient uptake (Helton et al., ), trophic dynamics (Anderson et al., ), effects of anthropogenic stressors (Prunier et al., ), and the joint roles of dispersal and environmental filtering in structuring taxonomic groups ranging from diatoms to fishes (Brown et al., ; de Mendoza et al., ; Jamoneau, Passy, Soininen, Leboucher, & Tison‐Roseberry, ; Schmera et al., ). Finally, the papers cover a broad geographic gradient from the Neotropics of Brazil (Valente‐Neto et al., ) to subarctic Finland (de Mendoza et al., ), thereby avoiding the typical bias to temperate riverine systems only.…”

“…These studies cover a wide range of topics and focal organisms, including disease spread (Carraro et al., ), nutrient uptake (Helton et al., ), trophic dynamics (Anderson et al., ), effects of anthropogenic stressors (Prunier et al., ), and the joint roles of dispersal and environmental filtering in structuring taxonomic groups ranging from diatoms to fishes (Brown et al., ; de Mendoza et al., ; Jamoneau, Passy, Soininen, Leboucher, & Tison‐Roseberry, ; Schmera et al., ). Finally, the papers cover a broad geographic gradient from the Neotropics of Brazil (Valente‐Neto et al., ) to subarctic Finland (de Mendoza et al., ), thereby avoiding the typical bias to temperate riverine systems only. A common theme among these studies is that the structure of the network and spatial dynamics do indeed regulate dynamics of populations and communities, and their associated functions.…”

“…Moreover, results from the study of de Mendoza et al. () indicated a greater importance of habitat heterogeneity over dispersal in determining insect metacommunity structure in a subarctic network of tributaries, which were directly connected to two mainstem rivers. Nevertheless, the spatial arrangement of their sampling sites did not allow for a strong test of dispersal dynamics in relation to network structure.…”