The plants and animals that inhabit river channels may act as zoogeomorphic agents affecting the nature and rates of sediment recruitment, transport and deposition. The impact of benthic‐feeding fish, which disturb bed material sediments during their search for food, has received very little attention, even though benthic feeding species are widespread in rivers and may collectively expend significant amounts of energy foraging across the bed. An ex situ experiment was conducted to investigate the impact of a benthic feeding fish (Barbel Barbus barbus) on particle displacements, bed sediment structures, gravel entrainment and transport fluxes. In a laboratory flume changes in bed surface topography were measured and grain displacements examined when an imbricated, water‐worked bed of 5.6 to 16 mm gravels was exposed to feeding juvenile Barbel (on average, 0.195 m in length). Grain entrainment rates and bedload fluxes were measured under a moderate transport regime for substrates that had been exposed to feeding fish and control substrates which had not. On average, approximately 37% of the substrate, by area, was modified by foraging fish during a four‐hour treatment period, resulting in increased microtopographic roughness and reduced particle imbrication. Structural changes by fish corresponded with an average increase in bedload flux of 60% under entrainment flows, whilst on average the total number of grains transported during the entrainment phase was 82% higher from substrates that had been disturbed by Barbel. Together, these results indicate that by increasing surface microtopography and undoing the naturally stable structures produced by water working, foraging can increase the mobility of gravel‐bed materials. An interesting implication of this result is that by increasing the quantity of available, transportable sediment and lowering entrainment thresholds, benthic feeding might affect bedload fluxes in gravel‐bed rivers. The evidence presented here is sufficient to suggest that further investigation of this possibility is warranted. Copyright © 2014 John Wiley & Sons, Ltd.

Summary Sedimentation and clogging of benthic and hyporheic zone substrata is increasingly being recognised as one of the greatest threats to the ecological integrity of riverine ecosystems globally. This ex situ study examined the influence of sedimentation (surface and subsurface) and pattern of hydrological exchange on the vertical distribution of the freshwater shrimp Gammarus pulex within the experimental substrata of running water mesocosms. Six sediment treatments representing a continuum from a clean gravel substratum to heavy sediment loading of both surface (benthic) and subsurface (hyporheic) substrata were used to examine the distribution of G. pulex in relation to the direction of hydrological exchange (downwelling, upwelling and no exchange). The distribution of G. pulex between the sediment layers was dependent on the pattern of hydrological exchange, sediment treatment and the interaction between these two factors. Sedimentation of the surface layer under no‐exchange conditions resulted in a lower proportion of G. pulex being recorded in the benthic sediments, whilst there were no significant differences under downwelling and upwelling flow conditions. Sedimentation of multiple layers of the column (benthic and subsurface) reduced the ability of individuals to utilise the subsurface layers of the substratum (i.e. the hyporheic zone) under no‐exchange and upwelling conditions. However, with downwelling conditions, the abundance of G. pulex declined with depth regardless of the fine sediment distribution or volume. This study demonstrates that faunal movement, and use of benthic and hyporheic substrata, may be influenced by sedimentation and modified by the pattern of vertical hydrological exchange. Severe sedimentation (colmation) has the potential to prevent benthic fauna from accessing the hyporheic zone and its resources which may ultimately lead to a reduction in stream diversity and metabolism, thereby limiting overall productivity and lotic ecosystem resilience.

Mixtures of three types of transparent sediment of varying particle size were 37 combined to produce six treatments with differing interstitial pore volumes and, hence, 38 differing subsurface porosity. Macroinvertebrate vertical movements were measured 39 during incremental reductions in water level from 5 cm above to 20 cm below the 40 sediment surface. These species comprised a variety of trait categories including 41 feeding group, species affinity to temporary streams and subsurface habitats. Active 42 and passive vertical movements were determined by conducting experiments with 43 both live individuals and their cadavers.

Background Carnivorous plants are an ideal model system for evaluating the role of secondary metabolites in plant ecology and evolution. Carnivory is a striking example of convergent evolution to attract, capture and digest prey for nutrients to enhance growth and reproduction and has evolved independently at least ten times. Though the roles of many traits in plant carnivory have been well studied, the role of secondary metabolites in the carnivorous habit is considerably less understood. Scope This review provides the first synthesis of research in which secondary plant metabolites have been demonstrated to have a functional role in plant carnivory. From these studies we identify key metabolites for plant carnivory and their functional role, and highlight biochemical similarities across taxa. From this synthesis we provide new research directions for integrating secondary metabolites into understanding of the ecology and evolution of plant carnivory. Conclusions Carnivorous plants use secondary metabolites to facilitate prey attraction, capture, digestion and assimilation. We found ~170 metabolites for which a functional role in carnivory has been demonstrated. Of these, 26 compounds are present across genera that independently evolved a carnivorous habit, suggesting convergent evolution. Some secondary metabolites have been co-opted from other processes, such as defence or pollinator attraction. Secondary metabolites in carnivorous plants provide a potentially powerful model system for exploring the role of metabolites in plant evolution. They also show promise for elucidating how the generation of novel compounds, as well as the co-option of pre-existing metabolites, provides a strategy for plants to occupy different environments.

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