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 ...»»»»
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-km2 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.^^^^
