Spatial Configuration Of Habitats Research Articles

The topology of spatial networks affects stability in experimental metacommunities.

Understanding the drivers of community stability has been a central goal in ecology. Traditionally, emphasis has been placed on studying the effects of biotic interactions on community variability, and less is understood about how the spatial configuration of habitats promotes or hinders metacommunity stability. To test the effects of contrasting spatial configurations on metacommunity stability, I designed metacommunities with patches connected as random or scale-free networks. In these microcosms, two prey and one protist predator dispersed, and I evaluated community persistence, tracked biomass variations, and measured synchrony between local communities and the whole metacommunity. After 30 generations, scale-free metacommunities had lower global biomass variability and higher persistence, suggesting higher stability. Synchrony between patches was lower in scale-free metacommunities. Patches in scale-free metacommunities showed a positive relationship between variability and patch connectivity, indicating higher stability in isolated communities. No clear relationship between variability and patch connectivity was observed in random networks. These results suggest the increased heterogeneity in connectivity of scale-free networks favours the prevalence of isolated patches of the metacommunity, which likely act as refugia against competition-the dominant interaction in this system-resulting in higher global stability. These results highlight the importance of accounting for network topology in the study of spatial dynamics.

Habitat fragmentation matters more than habitat loss: The case of host-parasite interactions.

While ecologists agree that habitat loss has a substantial negative effect on biodiversity it is still very much a matter of debate whether habitat fragmentation has a lesser effect and whether this effect is positive or negative for biodiversity. Here, we assess the relative influence of tropical forest loss and fragmentation on the prevalence of vector-borne blood parasites of the genera Plasmodium and Haemoproteus in six forest bird species. We also determine whether habitat loss and fragmentation are associated with a rise or fall in prevalence. We sample more than 4000 individual birds from 58 forest sites in Guadeloupe and Martinique. Considering 34 host-parasite combinations independently and a fine characterization of the amount and spatial configuration of habitat, we use partial least square regressions to disentangle the relative effects of forest loss, forest fragmentation, landscape heterogeneity, and local weather conditions on spatial variability of parasite prevalence. Then we test for the magnitude and the sign of the effect of each environmental descriptor. Strikingly, we show that forest fragmentation explains twice as much of the variance in prevalence as habitat loss or landscape heterogeneity. In addition, habitat fragmentation leads to an overall rise in prevalence in Guadeloupe, but its effect is variable in Martinique. Both habitat loss and landscape heterogeneity exhibit taxon-specific effects. Our results suggest that habitat loss and fragmentation may have contrasting effects between tropical and temperate regions and that inter-specific interactions may not respond in the same way as more commonly used biodiversity metrics such as abundance and diversity.

Assessing the influence of the amount of reachable habitat on genetic structure using landscape and genetic graphs.

Genetic structure, i.e. intra-population genetic diversity and inter-population genetic differentiation, is influenced by the amount and spatial configuration of habitat. Measuring the amount of reachable habitat (ARH) makes it possible to describe habitat patterns by considering intra-patch and inter-patch connectivity, dispersal capacities and matrix resistance. Complementary ARH metrics computed under various resistance scenarios are expected to reflect both drift and gene flow influence on genetic structure. Using an empirical genetic dataset concerning the large marsh grasshopper (Stethophyma grossum), we tested whether ARH metrics are good predictors of genetic structure. We further investigated (i) how the components of the ARH influence genetic structure and (ii) which resistance scenario best explains these relationships. We computed local genetic diversity and genetic differentiation indices in genetic graphs, and ARH metrics in the unified and flexible framework offered by landscape graphs, and we tested the relationships between these variables. ARH metrics were relevant predictors of the two components of genetic structure, providing an advantage over commonly used habitat metrics. Although allelic richness was significantly explained by three complementary ARH metrics in the best PLS regression model, private allelic richness and MIW indices were essentially related with the ARH measured outside the focal patch. Considering several matrix resistance scenarios was also key for explaining the different genetic responses. We thus call for further use of ARH metrics in landscape genetics to explain the influence of habitat patterns on the different components of genetic structure.

Applying systematic conservation planning to improve the allocation of restoration actions at multiple spatial scales

Ecological restoration is increasingly being upscaled to larger spatial scales of tens to hundreds of kilometers. Yet the complex logistics and high costs of ecological restoration mean that actions must be placed strategically at local scales of tens of meters to maximize ecological benefits and reduce socioeconomic costs. Despite the purported use of systematic planning tools for allocating restoration effort, the uptake and implementation of data‐driven restoration planning and ecological goal setting remains poor in many restoration programs. Here we demonstrate how the sequential workflows of systematic conservation planning can be translated to restoration at two spatial scales to enhance estuarine fisheries in eastern Australia. We select estuaries where restoration is feasible and recommended based on quantitative regional ecological goals (i.e. regional‐scale prioritization), and then identify potential restoration sites at smaller spatial scales within estuaries based on the principles of spatial ecology to ensure that the success and benefits of restoration are maximized (i.e. local‐scale prioritization). At the regional scale, we identified four levels of restoration priorities (very high, high, intermediate, and low) using quantitative ecological goals and the current ecological understanding of each system. At the local scale, we used spatially explicit Bayesian belief networks to identify sites that maximize restoration outcomes based on the environmental niche of habitat‐forming species and the spatial configuration of habitats that maximizes their use by fish. We show that using systematic frameworks can become an essential tool to optimize restoration investments at multiple scales as efforts upscale globally.

Fine-scale responses of mobile invertebrates and mesopredatory fish to habitat configuration

As habitat-forming species continue to decline globally, it is important to understand how associated communities respond to habitat loss and fragmentation. Changes in the density and spatial configuration of habitat have important consequences for associated communities. However, tests of these factors are often confounded by morphological variation of habitat-formers, which can be resolved by using standardised habitat-mimics. Furthermore, few studies have incorporated the role of predators in mediating the observed effects. To test whether predators mediate the abundance of invertebrates among algal habitats of varying configuration (isolated vs patches, and positions within patches), we placed macroalgal mimics into subtidal estuarine habitats for one month to sample epifaunal communities. At the same time, we conducted underwater video surveys of fish communities to quantify fish communities and their feeding behaviour among the artificial habitats. Isolated habitats did not differ from patch habitats, however, patch edges had the highest epifaunal abundance, where fish were least commonly observed. Observed fish feeding was highest in the middle of patches and increased fish observations and feeding in habitats with reduced epifaunal communities suggest that mesopredatory fish are mediating epifauna in patches, with predation pressure altered by the spatial configuration of the habitat. This contrasts to previous studies that focus on predators that congregate outside patches and suggest that fragmentation leads to reduced invertebrate abundance at habitat edges in contrast to centres. However, this study highlights that in habitat patches housing small mesopredators that also benefit from the increased structure, the centre of the patch experiences higher predation and therefore fewer epifauna in contrast to patch edges and individual algal mimics.

Disturbance type determines how connectivity shapes ecosystem resilience

Connectivity is fundamentally important for shaping the resilience of complex human and natural networks when systems are disturbed. Ecosystem resilience is, in part, shaped by the spatial arrangement of habitats, the permeability and fluxes between them, the stabilising functions performed by organisms, their dispersal traits, and the interactions between functions and stressor types. Controlled investigations of the relationships between these phenomena under multiple stressors are sparse, possibly due to logistic and ethical difficulties associated with applying and controlling stressors at landscape scales. Here we show that grazing performance, a key ecosystem function, is linked to connectivity by manipulating the spatial configuration of habitats in microcosms impacted by multiple stressors. Greater connectivity enhanced ecosystem function and reduced variability in grazing performance in unperturbed systems. Improved functional performance was observed in better connected systems stressed by harvesting pressure and temperature rise, but this effect was notably reversed by the spread of disease. Connectivity has complex effects on ecological functions and resilience, and the nuances should be recognised more fully in ecosystem conservation.

Seascape Configuration Leads to Spatially Uneven Delivery of Parrotfish Herbivory across a Western Indian Ocean Seascape

Spatial configuration of habitat types in multihabitat seascapes influence ecological function through links of biotic and abiotic processes. These connections, for example export of organic matter or fishes as mobile links, define ecosystem functionality across broader spatial scales. Herbivory is an important ecological process linked to ecosystem resilience, but it is not clear how herbivory relates to seascape configuration. We studied how herbivory and bioerosion by 3 species of parrotfish were distributed in a multi-habitat tropical seascape in the Western Indian Ocean (WIO). We surveyed the abundance of three species with different life histories—Leptoscarus vaigiensis (seagrass species), Scarus ghobban (juvenile-seagrass/adults-reefs) and Scarus rubroviolaceus (reef species) —in seagrass meadows and on reefs and recorded their selectivity of feeding substrate in the two habitats. Herbivory rates for L. vaigiensis and S. ghobban and bioerosion for S. rubroviolaceus were then modelled using bite rates for different size classes and abundance and biomass data along seascape gradients (distance to alternative habitat types such as land, mangrove and seagrass). Bioerosion by S. rubroviolaceus was greatest on reefs far from seagrass meadows, while herbivory rates by S. ghobban on reefs displayed the opposite pattern. Herbivory in seagrass meadows was greatest in meadows close to shore, where L. vaigiensis targeted seagrass leaves and S. ghobban the epiphytes growing on them. Our study shows that ecological functions performed by fish are not equally distributed in the seascape and are influenced by fish life history and the spatial configuration of habitats in the seascape. This has implications for the resilience of the system, in terms of spatial heterogeneity of herbivory and bioerosion and should be considered in marine spatial planning and fisheries management.

Measuring impacts on species with models and metrics of varying ecological and computational complexity.

Approaches to assess the impacts of landscape disturbance scenarios on species range from metrics based on patterns of occurrence or habitat to comprehensive models that explicitly include ecological processes. The choice of metrics and models affects how impacts are interpreted and conservation decisions. We explored the impacts of 3 realistic disturbance scenarios on 4 species with different ecological and taxonomic traits. We used progressively more complex models and metrics to evaluate relative impact and rank of scenarios on the species. Models ranged from species distribution models that relied on implicit assumptions about environmental factors and species presence to highly parameterized spatially explicit population models that explicitly included ecological processes and stochasticity. Metrics performed consistently in ranking different scenarios in order of severity primarily when variation in impact was driven by habitat amount. However, they differed in rank for cases where dispersal dynamics were critical in influencing metapopulation persistence. Impacts of scenarios on species with low dispersal ability were better characterized using models that explicitly captured these processes. Metapopulation capacity provided rank orders that most consistently correlated with those from highly parameterized and data-rich models and incorporated information about dispersal with little additional computational and data cost. Our results highlight the importance of explicitly considering species' ecology, spatial configuration of habitat, and disturbance when choosing indicators of species persistence. We suggest using hybrid approaches that are a mixture of simple and complex models to improve multispecies assessments.

Holocene extinctions of a top predator-Effects of time, habitat area and habitat subdivision.

Loss of habitat and changes in the spatial configuration of habitats are major drivers of species extinctions, but the responses to these drivers differ between organisms. To advance theory on how extinction risk from different types of habitat alteration relates to species-specific traits, there is a need for studies of the long-term extinction dynamic of individual species. The goal of this study was to quantify how habitat area and the spatial configuration of habitats affect extinction rate of an aquatic top predator, the northern pike Esox lucius L. We recorded the presence/absence of northern pike in 398 isolated habitat fragments, each one consisting of a number of interconnected lakes. Time since isolation of the habitat fragments, caused by cut-off from the main dispersal source in the Baltic Sea, varied between 0 and 10,000years. Using survival regression, we analysed how pike population survival was affected by time since isolation, habitat size and habitat subdivision. The approach builds on the assumptions that pike colonized all fragments before isolation and that current absences result from extinctions. We verified these assumptions by testing (a) if pike was present in the region throughout the entire time period when the lakes formed and (b) if pike typically colonize lakes that are formed today. We also addressed the likelihood that unrecorded anthropogenic introductions could bias our estimates of extinction rate. Our results supported the interpretation that current patterns of presence/absence in our study system are shaped by extinctions. Further, we found that time since isolation and fragment area had strong effects on pike population survival. In contrast, spatial habitat subdivision (i.e. if a fragment contained few large lakes or many small lakes) and other environmental covariates describing climate and productivity were unrelated to pike survival. Over all, extinction rate was high in young fragments and decreased sharply with increasing fragment age. Our study demonstrates how the link between extinction rate and habitat size and spatial structure can be quantified. More similar studies may help us find generalizations that can guide management of habitat size and connectivity.

Importance of spatial configuration of deadwood habitats in species conservation.

Article impact statement: Use occurrence patterns and spatial population dynamics of deadwood‐dependent organisms to evaluate importance of spatial habitat configuration.

Beyond isolation by distance: What best explains functional connectivity among populations of three sympatric plant species in an ancient terrestrial island system?

AbstractAimUnderstanding how landscape features affect gene flow is critical to connectivity conservation and restoration management. Here, we examined the relationship between functional connectivity (gene flow) and structural connectivity (area and spatial configuration of habitats) in three co‐occurring short‐range plant taxa in an ancient terrestrial island system.LocationLow‐altitude mountain range south‐western Australia.MethodsWe analysed spatial patterns of genetic differentiation at nuclear microsatellite loci using Bayesian clustering. Circuit theory modelling was used to generate all possible pathways that connect populations as resistance distance matrices based on two surfaces for each taxon. The first surface assumes a flat terrain and tests whether genetic similarity declines only with distance—isolation by distance (IBD). The second surface is habitat suitability based on species distribution modelling (SDM), which tests whether genetic similarity is a function of connected and suitable habitat. Multiple matrix regression with randomization was used to test the significance of the resistance distance matrices at predicting two metrics of genetic differentiation (FST and DEST). Variance explained was partitioned using redundancy analysis.ResultsGenetic structure for the insect‐pollinated taxa—Acacia adinophylla—and Tetratheca aphylla subsp. aphylla was at similar spatial scales. Unexpectedly, a higher level of genetic structure was found in the wind‐pollinated Lepidosperma bungalbin. IBD best explained the gene flow of A. adinophylla (R2 = 0.41–0.43) with partial support provided by habitat suitability (R2 = 0.04–0.07). In contrast, connectivity by habitat suitability was highest for T. aphylla subsp. aphylla (R2 = 0.56–0.59). Drivers of L. bungalbin connectivity were inconsistent between the two measures of genetic differentiation.Main conclusionsGene flow is facilitated by different factors for the three taxa. Habitat fragmentation would most strongly impede gene flow for T. aphylla subsp. aphylla. Geographical distance cannot be assumed as the sole or best determinant of gene flow among populations, nor can findings be generalized to coexisting taxa.

Monitoring program design for data-limited marine biogenic habitats: A structured approach.

Marine biogenic habitats—habitats created by living organisms—provide essential ecosystem functions and services, such as physical structuring, nutrient cycling, biodiversity support, and increases in primary, secondary, and tertiary production. With the growing trend toward ecosystem approaches to marine conservation and fisheries management, there is greater emphasis on rigorously designed habitat monitoring programs. However, such programs are challenging to design for data‐limited habitats for which underlying ecosystem processes are poorly understood. To provide guidance in this area, we reviewed approaches to benthic assessments across well‐studied marine biogenic habitats and identified common themes related to indicator selection, sampling methods, and survey design. Biogenic habitat monitoring efforts largely focus on the characteristics, distribution, and ecological function of foundation species, but may target other habitat‐forming organisms, especially when community shifts are observed or expected, as well as proxies of habitat status, such as indicator species. Broad‐scale methods cover large spatial areas and are typically used to examine the spatial configuration of habitats, whereas fine‐scale methods tend to be laborious and thus restricted to small survey areas, but provide high‐resolution data. Recent, emerging methods enhance the capabilities of surveying large areas at high spatial resolution and improve data processing efficiency, bridging the gap between broad‐ and fine‐scale methods. Although sampling design selection may be limited by habitat characteristics and available resources, it is critically important to ensure appropriate matching of ecological, observational, and analytical scales. Drawing on these common themes, we propose a structured, iterative approach to designing monitoring programs for marine biogenic habitats that allows for rigorous data collection to inform management strategies, even when data and resource limitations are present. A practical application of this approach is illustrated using glass sponge reefs—a recently discovered and data‐limited habitat type—as a case study.

Modeling the effects of landscape patterns of current forests on the habitat quality of historical remnants in a highly urbanized area

The fragmentation of natural habitats by urbanization often results in small and isolated remnants that lead to the degeneration of ecosystem services (ESs) and a loss of biodiversity. However, our understanding of the effects of landscape patterns on the provisioning of ESs in urban areas remains limited, as few studies have distinguished historical forest remnants (HFRs) from recently established habitats or have quantified changes in ESs due to HFRs. This study measured changes in the extent of forest ecosystems and the role played by HFRs in generating ESs in the human-dominated modernized landscape of Seoul, Republic of Korea. We use the spatial configuration of habitats to measure an index of habitat quality as an ES for a target conservation objective of general terrestrial biodiversity. Land-cover maps from two periods were used to identify 37 isolated patches within current parks with HFRs. Then landscape patterns and modeled habitat quality and habitat units (HUs) were quantified. Pearson correlation coefficients and forward stepwise multiple regression were used to examine the landscape metrics combined with HUs to explore key indicators that affect the HUs-value of HFRs. A 35.31% decline in total HUs was observed due to a significant decline in total forest area; however, the HUs of the HFRs increased by 0.5%. The shapes of current forests may positively affect the biodiversity of HFRs, whereas the area of newly formed habitats may negatively affect biodiversity in our modeling results. Thus, the careful design of newly formed habitats during city planning should include the preservation of historical remnants.

Is habitat fragmentation good for biodiversity?

Habitat loss is a primary threat to biodiversity across the planet, yet contentious debate has ensued on the importance of habitat fragmentation ‘per se’ (i.e., altered spatial configuration of habitat for a given amount of habitat loss). Based on a review of landscape-scale investigations, Fahrig (2017; Ecological responses to habitat fragmentation per se. Annual Review of Ecology, Evolution, and Systematics 48:1-23) reports that biodiversity responses to habitat fragmentation ‘per se’ are more often positive rather than negative and concludes that the widespread belief in negative fragmentation effects is a ‘zombie idea’. We show that Fahrig's conclusions are drawn from a narrow and potentially biased subset of available evidence, which ignore much of the observational, experimental and theoretical evidence for negative effects of altered habitat configuration. We therefore argue that Fahrig's conclusions should be interpreted cautiously as they could be misconstrued by policy makers and managers, and we provide six arguments why they should not be applied in conservation decision-making. Reconciling the scientific disagreement, and informing conservation more effectively, will require research that goes beyond statistical and correlative approaches. This includes a more prudent use of data and conceptual models that appropriately partition direct vs indirect influences of habitat loss and altered spatial configuration, and more clearly discriminate the mechanisms underpinning any changes. Incorporating these issues will deliver greater mechanistic understanding and more predictive power to address the conservation issues arising from habitat loss and fragmentation.

Eco-evolutionary feedbacks following changes in spatial connectedness.

Humans are drastically changing the spatial configuration of habitats. The associated changes in habitat connectedness impose strong selection on dispersal, and dispersal related traits. Evolutionary responses do, however, strongly feedback on the metapopulation dynamics, by further constraining or improving connectivity and impacting local population and food web dynamics. Because these spatial eco-evolutionary interactions occur at contemporary time scales, unique evidence on its importance is especially emerging in the field of entomology as many insects have short generation times and a huge reproductive potential. We review the ecological feedbacks originating from the evolution of dispersal rate, dispersal syndromes and genetic diversity on metapopulation dynamics and range expansions. We thus close the eco-evolutionary loop for insect and arachnid spatial dynamics.

Evaluating the Impacts of Hunting Paths on Northern Bobwhite Survival, Economic Costs, and Hunter Satisfaction

The amount and spatial configuration of habitat is known to influence the abundance, movements, resource use, and persistence of many species. As such, land managers must be judicious in their application of management actions to minimize its impact on wildlife while concurrently providing recreational opportunities. Mowing or roller-chopping is a common management technique implemented on intensively managed northern bobwhite (Colinus virginianus) plantations to increase hunter accessibility, provide travel corridors for pointing dogs, manage vegetation succession, among other benefits. Managers typically create hunting paths in a grid pattern at 30 ft spacing resulting in approximately 35% of vegetation removed prior to hunting season. However, the optimal spacing for paths is unknown and some concern exists over the presence of paths in general as they may facilitate predation. Our objectives were to determine how different densities of paths (i.e., reduced cover and increased edge) impacted northern bobwhite survival, quantify the costs per hectare of paths, and determine hunter satisfaction. We developed two path treatments (30 ft and 90 ft spacing) and a control (no paths) on Tall Timbers Research Station in Leon County, Florida. We radio-tagged a subset of northern bobwhites (n = 150), equally distributed within each treatment, and monitored survival in each treatment using radio-telemetry during the non-breeding season (October through April) in 2013-2016. We used Burnham’s joint model within program MARK to compare survival of radio-tagged bobwhites among treatment groups. We analyzed data collected from a hand-held global positioning system used to delineate paths during creation to compute implementation cost. Hunter satisfaction was assessed using a pre- and post-hunt survey. Optimization will be used to determine which treatment achieves the greatest utility under current management objectives. Results of this research will provide managers information to make informed decisions about the implementation of hunting paths under various management scenarios.

Dispersal: a central and independent trait in life history

The study of tradeoffs among major life history components (age at maturity, lifespan and reproduction) allowed the development of a quantitative framework to understand how environmental variation shapes patterns of biodiversity among and within species.Because every environment is inherently spatially structured, and in most cases temporally variable, individuals need to move within and among habitats to maximize fitness. Dispersal is often assumed to be tightly integrated into life histories through genetic correlations with other vital traits. This assumption is particularly strong within the context of a fast‐slow continuum of life‐history variation. Such a framework is to date used to explain many aspects of population and community dynamics. Evidence for a consistent and context‐independent integration of dispersal in life histories is, however, weak. We therefore advocate the explicit integration of dispersal into life history theory as a principal axis of variation influencing fitness, that is free to evolve, independently of other life history traits.We synthesize theoretical and empirical evidence on the central role of dispersal and its evolutionary dynamics on the spatial distribution of ecological strategies and its impact on population spread, invasions and coexistence. By applying an optimality framework we show that the inclusion of dispersal as an independent dimension of life histories might substantially change our view on evolutionary trajectories in spatially structured environments.Because changes in the spatial configuration of habitats affect the costs of movement and dispersal, adaptations to reduce these costs will increase phenotypic divergence among and within populations. We outline how this phenotypic heterogeneity is anticipated to further impact population and community dynamics.

Spatial configuration matters: a test of the habitat amount hypothesis for plants in calcareous grasslands

A recent hypothesis, the habitat amount hypothesis, predicts that the total amount of habitat in the landscape can replace habitat patch size and isolation in studies of species richness in fragmented landscapes. To test the habitat amount hypothesis by first evaluating at which spatial scale the relationship between species richness in equal-sized sample quadrats and habitat amount was the strongest, and then test the importance of spatial configuration of habitat—measured as local patch size and isolation—when habitat amount was taken into account. A quasi-experimental setup with 20 habitat patches of dry calcareous grasslands varying in patch size, patch isolation and habitat amount at the landscape scale was established in the inner Oslo fjord, Southern Norway. We recorded species richness of habitat specialists of vascular plants in equal-sized sample quadrats and analysed the relationship between species richness, habitat amount in the landscape and patch size and isolation. Although the total amount of habitat in a 3 km-radius around the local patch was positively related to species richness in the sample quadrats, local patch size had an additional positive effect, and the effect of patch size was higher when the amount of habitat within the 3 km-radius was high than when it was low. In our study system of specialist vascular plants in dry calcareous grasslands, we do not find support for the habitat amount hypothesis.

A synthesis of genetic connectivity in deep-sea fauna and implications for marine reserve design.

With anthropogenic impacts rapidly advancing into deeper waters, there is growing interest in establishing deep-sea marine protected areas (MPAs) or reserves. Reserve design depends on estimates of connectivity and scales of dispersal for the taxa of interest. Deep-sea taxa are hypothesized to disperse greater distances than shallow-water taxa, which implies that reserves would need to be larger in size and networks could be more widely spaced; however, this paradigm has not been tested. We compiled population genetic studies of deep-sea fauna and estimated dispersal distances for 51 studies using a method based on isolation-by-distance slopes. Estimates of dispersal distance ranged from 0.24km to 2028km with a geometric mean of 33.2km and differed in relation to taxonomic and life-history factors as well as several study parameters. Dispersal distances were generally greater for fishes than invertebrates with the Mollusca being the least dispersive sampled phylum. Species that are pelagic as adults were more dispersive than those with sessile or sedentary lifestyles. Benthic species from soft-substrate habitats were generally less dispersive than species from hard substrate, demersal or pelagic habitats. As expected, species with pelagic and/or feeding (planktotrophic) larvae were more dispersive than other larval types. Many of these comparisons were confounded by taxonomic or other life-history differences (e.g. fishes being more dispersive than invertebrates) making any simple interpretation difficult. Our results provide the first rough estimate of the range of dispersal distances in the deep sea and allow comparisons to shallow-water assemblages. Overall, dispersal distances were greater for deeper taxa, although the differences were not large (0.3-0.6 orders of magnitude between means), and imbalanced sampling of shallow and deep taxa complicates any simple interpretation. Our analyses suggest the scales of dispersal and connectivity for reserve design in the deep sea might be comparable to or slightly larger than those in shallow water. Deep-sea reserve design will need to consider the enormous variety of taxa, life histories, hydrodynamics, spatial configuration of habitats and patterns of species distributions. The many caveats of our analyses provide a strong impetus for substantial future efforts to assess connectivity of deep-sea species from a variety of habitats, taxonomic groups and depth zones.

Net rate of energy intake predicts reach-level steelhead (Oncorhynchus mykiss) densities in diverse basins from a large monitoring program

Substantial research effort has been devoted to understanding stream-dwelling salmonids’ use of summer rearing and growth habitat, with a subset of studies focusing on foraging position selection and the energetic trade-offs of differential habitat use. To date, however, cost–benefit analyses for most foraging model studies have focused on small sampling areas such as individual habitat units. To address this knowledge gap, we applied a mechanistic foraging model to 22 stream reaches (100–400 m) from two watersheds within the Columbia River Basin. We found a strong, positive correlation (R2= 0.61, p < 0.001) between predicted carrying capacities and observed fish densities. Predicted proportion of suitable habitat was weakly correlated with observed fish density (R2= 0.18, p = 0.051), but the mean net rate of energy intake prediction in sampling reaches was not a significant predictor of observed fish biomass. Our results suggest spatial configuration of habitat, in addition to quantity and quality, is an important determinant of habitat use. Further, carrying capacity predicted by the model shows promise as a habitat metric. We also evaluated the feasibility of applying this data-intensive modeling approach in a large-scale monitoring program to examine habitat quality and quantity. Though the approach can be computationally expensive, we feel the model’s ability to integrate physical habitat metrics (e.g., depth, velocity) with important biological considerations like food availability and temperature is a benefit that far outweighs associated costs. We feel this modeling approach has great potential as a tool to help understand habitat use in drift-feeding fishes.