Dispersal as a limiting factor in the colonization of restored mountain streams by plants and macroinvertebrates

Abstract

Summary 1.Over the past centuries, European streams have been heavily influenced by humans through pollution and regulation. As a result, the quality and diversity of freshwater riparian habitats have declined strongly, and the diversity of riparian flora and fauna has decreased. Recent restoration measures have resulted in stream habitat improvements, but biodiversity improvements have failed to follow in fragmented streams. It has been suggested that dispersal limitation could play an important role in the lack of biodiversity improvement in restored streams, but to date, there is no conclusive evidence for this assumption. 2. In this study, we investigated whether colonization of restored streams by plants and macroinvertebrates is limited by dispersal. We hypothesized that colonization success increases with increasing availability of (nearby) source populations and with increasing ability of species to disperse over long distances. We related species composition in seven restored stream sections to species' abundances in the surroundings and to species' dispersal abilities. 3. For both plants and macroinvertebrates, colonization success is strongly related to the abundance of species in the local and regional species pools. 4. For plants, dispersal strategy has an additional influence on colonization success: short-lived plants with high production of small, well-dispersed seeds colonized best within the 3-to 5-year period after restoration. 5. The existence of dispersal strategy constraints could not be confirmed in macroinvertebrates, possibly because these are limited by a lack of connectivity on larger spatial scales. On the landscape scale, beneficial effects of increased plant diversity might further improve habitat suitability for macroinvertebrates. 6. Synthesis and applications. Dispersal appears to be a limiting factor for successful (re)colonization of restored streams in fragmented landscapes. In plants, this is attributed to limitations in seed dispersal abilities and likely to a lack of nearby source populations as well. In macroinvertebrates, lack of nearby source populations may also be a limiting factor. Hence, we suggest restoring landscape connectivity at larger spatial scales and optimizing the availability of near-natural 'source' areas in the vicinity of restoration projects, at least for plants, to improve the success of biodiversity restoration in fragmented habitats.

Recovery of a mining-damaged stream ecosystem

“…Dispersal abilities by air or drift vary greatly among freshwater invertebrates, but are usually reported as <1 km per generation, and dispersal is often from downstream to upstream (Mackay, 1992;Elliott, 2003;MacNeale et al, 2005). Perennial tributaries with clean-water refugia areas are present along Panther Creek (Figure 1), suggesting dispersal is unlikely a persistent limiting factor in recovery of stream insects in our study area, unlike some areas (Masters et al, 2007;Milner et al, 2008;Brederveld et al, 2011). Still, sites in lower Panther Creek (PA-km17 and km22) could be distant enough from large clean water tributaries that dispersal distances contribute to a lag in the recovery of benthic communities following water quality improvements.…”

Aquatic Plant Dynamics in Lowland River Networks: Connectivity, Management and Climate Change

“…The role of longitudinal connectivity in river networks is gaining momentum in conservation [122,123] and restoration [124,125] yet support for its role in those highly managed rivers, independently of other exogenous factors, was surprisingly weak (Figure 12). This may point to the role of small weirs in preventing longitudinal dispersion of propagules.…”

Guidelines for Using Movement Science to Inform Biodiversity Policy

“…Movement ecology, to a limited extent, & Philip S. Barton philip.barton@anu.edu.au already influences biodiversity policy and management. Assisted colonization as a response to climate change (Shirey and Lamberti 2010) and restoration of fragmented landscapes (Brederveld et al 2011;Woodcock et al 2012) are examples where limitations to dispersal or colonization potential require information about species' movement. However, the application of movement ecology research to biodiversity conservation requires substantial improvement to better reflect recent advances in knowledge and techniques .…”