Dispersal strength determines meta‐community structure in a dendritic riverine network

Abstract

Aim Meta-community structure is a function of both local (site-specific) and regional (landscape-level) ecological factors, and the relative importance of each may be mediated by the dispersal ability of organisms. Here, we used aquatic invertebrate communities to investigate the relationship between local and regional factors in explaining distance decay relationships (DDRs) in fragmented dendritic stream networks.Location Dryland streams distributed within a 400-km 2 section of the San Pedro River basin, south-eastern Arizona, USA.Methods We combined fine-scale local information (flow and habitat characteristics) with regional-scale information to explain DDR patterns in community composition of aquatic invertebrate species with a wide range of dispersal abilities. We used a novel application of a landscape resistance modelling approach (originally developed for landscape genetic studies) that simultaneously assessed the importance of local and regional ecological factors as well as dispersal ability of organisms.Results We found evidence that both local and regional factors influenced aquatic invertebrate DDRs in dryland stream networks, and the importance of each factor depended on the dispersal capacities of the organisms. Local and weak dispersers were more affected by site-specific factors, intermediate dispersers by landscape-level factors, and strong dispersers showed no discernable pattern. This resulted in a strongly hump-shaped relationship between dispersal ability and landscape-level factors, where only moderate dispersers showed evidence of DDRs. Unlike most other studies of dendritic networks, our results suggest that overland pathways, using perennial refugia as stepping-stones, might be the main dispersal route in fragmented stream networks.Main conclusions We suggest that using a combination of landscape and local distance measures can help to unravel meta-community patterns in dendritic systems. Our findings have important conservation implications, such as the need to manage river systems for organisms that span a wide variety of dispersal abilities and local ecological requirements. Our results also highlight the need to preserve perennial refugia in fragmented networks, as they may ensure the viability of aquatic meta-communities by facilitating dispersal.

Experimentally disentangling the influence of dispersal and habitat filtering on benthic invertebrate community structure

“…Network structure and dispersal can interact with larger scale habitat variables like drying and elevation Bogan, Boersma, & Lytle, 2013;Canedo-Arguelles et al, 2015;Leigh & Datry, 2017) and that these interactions can be highly context dependent (Heino, Gr€ onroos, Soininen, et al, 2012;Tonkin, Heino, Sundermann, Haase, & J€ ahnig, 2016;Schmera et al 2017). Even on smaller spatial scales like the stream reach scale, natural complexity and habitat variability can directly affect the process of macroinvertebrate dispersal (Brooks, Wolfenden, Downes, & Lancaster, 2017).…”

The relationship between least-cost and resistance distance

“…Two decades later McRae [2] applied this concept to model gene flow. Since then, circuit theory and associated software Circuitscape [2], has been used to simulate movement and gene flow of a multitude of species in the fields of ecology and evolution (e.g., [3], [4], [5], [6], [7]). At the same time, least-cost modelling has also been commonly used for very similar applications (e.g., [8], [9], [10], [11], [12]).…”

Macroinvertebrate and organic matter export from headwater tributaries of a Central Appalachian stream

“…In a separate study, seasonal and stream size factors in other headwater (Grubbs, 2011), particularly between the months of February and May. Spatial proximity of tributaries did not influence overall assemblage structure as commonly found in some distance-decay studies (e.g., Thompson & Townsend, 2006;Rouquette et al, 2013;Cañedo-Argüelles et al, 2015). In Appalachian streams of Maryland, Brown & Swan (2010) compared invertebrate communities from headwater tributary and mainstem sites and found that within the headwater sites, community similarity was mostly driven by local environmental factors, not spatial distance.…”

“…Although our study did not compare assemblages in tributaries with those in the mainstem Clemons Fork, but we acknowledge that Brown & Swan (2010) describes a phenomenon that likely occurs in our study area but requires further testing. In large-scale assessments (i.e., across wide geographic distances), proximity is often a strong driver of community structure with high taxa turnover rates over wide spatial gradients (Cañedo-Argüelles et al, 2015). Our study was confined to a relatively small stream network and this may have limited our ability to detect a distancedecay relationship.…”