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Explaining island-wide geographical patterns of Caribbean fish diversity: A multi-scale seascape ecology approach

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Geographical patterning of fish diversity across coral reef seascapes is driven by many interacting environmental variables operating at multiple spatial scales. Identifying suites of variables that explain spatial patterns of fish diversity is central to ecology and informs prioritization in marine conservation, particularly where protection of the highest biodiversity coral reefs is a primary goal. However, the relative importance of conventional within-patch variables versus the spatial patterning of the surrounding seascape is still unclear in the ecology of fishes on coral reefs. A multi-scale seascape approach derived from landscape ecology was applied to quantify and examine the explanatory roles of a wide range of variables at different spatial scales including: (i) within-patch structural attributes from field data (5 × 1 m2 sample unit area); (ii) geometry of the seascape from sea-floor maps (10–50 m radius seascape units); and wave exposure from a hydrodynamic model (240 m resolution) for 251 coral reef survey sites in the US Virgin Islands. Non-parametric statistical learning techniques using single classification and regression trees (CART) and ensembles of boosted regression trees (TreeNet) were used to: (i) model interactions; and (ii) identify the most influential environmental predictors from multiple data types (diver surveys, terrain models, habitat maps) across multiple spatial scales (1–196,350 m2). Classifying the continuous response variables into a binary category and instead predicting the presence and absence of fish species richness hotspots (top 10% richness) increased the predictive performance of the models. The best CART model predicted fish richness hotspots with 80% accuracy. The statistical interaction between abundance of living scleractinian corals measured by SCUBA divers within 1 m2 quadrats and the topographical complexity of the surrounding sea-floor terrain (150 m radius seascape unit) measured from a high-resolution terrain model best explained geographical patterns in fish richness hotspots. The comparatively poor performance of models predicting continuous variability in fish diversity across the seascape could be a result of a decoupling of the diversity-environment relationship owing to structural degradation leading to a widespread homogenization of coral reef structure.
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... mean, max, min, range, standard deviation) at a variety of spatial scales (e.g. metres to kilometres) (Knudby et al., 2011;Rees et al., 2018;Sekund & Pittman, 2017). Terrain metrics quantify properties of benthic ecosystems that underpin their role in providing habitat for fish, and variation in fish diversity and abundance has been linked to spatial variation in terrain metrics (e.g. ...
... However, many describe similar types of terrain variation and are therefore, characterized by high co-linearity with other similar terrain metrics (e.g. rugosity, slope, slope of slope) (Leitner et al., 2017;Monk et al., 2010;Sekund & Pittman, 2017). To better understand patterns of metric applications, we grouped terrain metrics into four categories based on similarities in the terrain features being indexed: ...
... seascape context), which shape the distribution, abundance and diversity of fish assemblages in most seascapes (Olson et al., 2019;Ortodossi et al., 2019;Perry et al., 2018). Seafloor terrain can also modify the movement of fish species between different habitats, and these properties likely interact with seascape context to determine the spatial distribution of fish populations (Moore et al., 2011;Sekund & Pittman, 2017;Wedding et al., 2019). We do not know, however, whether variation in the three-dimensional properties of the seafloor influence the effects of two-dimensional seascape context, and connectivity, on fish assemblages (research priority 3, Table 8). ...
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... Nevertheless, some broad groupings were evident. Several fish studies investigated the use of measures of complexity derived from relatively new remote data capture methods (LIDAR imagery from aircraft and satellites) to predict the distribution of coral reef species (Kuffner et al. 2007;Pittman et al., 2009;Walker et al. 2009;Knudby et al. 2010Knudby et al. , 2011Pittman and Brown, 2011;Catano et al. 2015;Sekund and Pittman, 2017;Stamoulis et al. 2018). Temperate studies often used hydroacoustic remote sensing, primarily investigating the efficacy of measures derived from multibeam echosounding (MBES) to model the distribution of fish in America (Iampietro et al., 2008;Young et al. 2010), Europe (Martin--Garcia et al. 2013) and Australia (Moore et al. 2009(Moore et al. , 2010Rees et al. 2013Rees et al. , 2018Cameron et al. 2014;Coleman et al. 2016;Galaiduk et al. 2017;Ferrari et al. 2018). ...
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... Purkis et al. (2008) also reported that bathymetric range derived over the smallest extents (4 m and 8 m radii) of those examined (4 m-200 m radii) were most important for territorial species. Slope of slope was also most important for Caribbean reef fish species richness when quantified over 25 m radii, comparable to the home range size of these fish (Sekund and Pittman, 2017). Failure to identify the spatial extent(s) relevant to each species could hinder or prevent identification of relationships, particularly if the biotic metric included the differencing responses of functionally or trophically dissimilar groups. ...
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Coral reefs and associated fish populations have experienced rapid decline in the Caribbean region and marine protected areas (MPAs) have been widely implemented to address this decline. The performance of no-take MPAs (i.e., marine reserves) for protecting and rebuilding fish populations is influenced by the movement of animals within and across their boundaries. Very little is known about Caribbean reef fish movements creating a critical knowledge gap that can impede effective MPA design, performance and evaluation. Using miniature implanted acoustic transmitters and a fixed acoustic receiver array, we address three key questions: How far can reef fish move? Does connectivity exist between adjacent MPAs? Does existing MPA size match the spatial scale of reef fish movements? We show that many reef fishes are capable of traveling far greater distances and in shorter duration than was previously known. Across the Puerto Rican Shelf, more than half of our 163 tagged fish (18 species of 10 families) moved distances greater than 1 km with three fish moving more than 10 km in a single day and a quarter spending time outside of MPAs. We provide direct evidence of ecological connectivity across a network of MPAs, including estimated movements of more than 40 km connecting a nearshore MPA with a shelf-edge spawning aggregation. Most tagged fish showed high fidelity to MPAs, but also spent time outside MPAs, potentially contributing to spillover. Three-quarters of our fish were capable of traveling distances that would take them beyond the protection offered by at least 40-64% of the existing eastern Caribbean MPAs. We recommend that key species movement patterns be used to inform and evaluate MPA functionality and design, particularly size and shape. A re-scaling of our perception of Caribbean reef fish mobility and habitat use is imperative, with important implications for ecology and management effectiveness.
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Coral reefs face a diverse array of threats, from eutrophication and overfishing to climate change. As live corals are lost and their skeletons eroded, the structural complexity of reefs declines. This may have important consequences for the survival and growth of reef fish because complex habitats mediate predator-prey interactions [1, 2] and influence competition [3-5] through the provision of prey refugia. A positive correlation exists between structural complexity and reef fish abundance and diversity in both temperate and tropical ecosystems [6-10]. However, it is not clear how the diversity of available refugia interacts with individual predator-prey relationships to explain emergent properties at the community scale. Furthermore, we do not yet have the ability to predict how habitat loss might affect the productivity of whole reef communities and the fisheries they support. Using data from an unfished reserve in The Bahamas, we find that structural complexity is associated not only with increased fish biomass and abundance, but also with nonlinearities in the size spectra of fish, implying disproportionately high abundances of certain size classes. By developing a size spectrum food web model that links the vulnerability of prey to predation with the structural complexity of a reef, we show that these nonlinearities can be explained by size-structured prey refugia that reduce mortality rates and alter growth rates in different parts of the size spectrum. Fitting the model with data from a structurally complex habitat, we predict that a loss of complexity could cause more than a 3-fold reduction in fishery productivity.
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Coral reefs are complex, heterogeneous environments where it is common for the features of interest to be smaller than the spatial dimensions of imaging sensors. While the coverage of live coral at any point in time is a critical environmental management issue, image pixels may represent mixed proportions of coverage. In order to address this, we describe the development, application, and testing of a spectral index for mapping live coral cover using CASI-2 airborne hyperspectral high spatial resolution imagery of Heron Reef, Australia. Field surveys were conducted in areas of varying depth to quantify live coral cover. Image statistics were extracted from co-registered imagery in the form of reflectance, derivatives, and band ratios. Each of the spectral transforms was assessed for their correlation with live coral cover, determining that the second derivative around 564 nm was the most sensitive to live coral cover variations(r(2) = 0.63). Extensive field survey was used to transform relative to absolute coral cover, which was then applied to produce a live coral cover map of Heron Reef. We present the live coral cover index as a simple and viable means to estimate the amount of live coral over potentially thousands of km(2) and in clear-water reefs.
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Theoretical models predict strong influences of habitat loss and fragmentation on species distributions and demography, but empirical studies have shown relatively inconsistent support across species and systems. We argue that species’ responses to landscape-scale habitat loss and fragmentation are likely to appear less idiosyncratic if it is recognized that species perceive the same landscapes in different ways. We present a new quantitative approach that uses species distribution models (SDMs) to measure landscapes (e.g. patch size, isolation, matrix amount) from the perspective of individual species. First, we briefly summarize the few efforts to date demonstrating that once differences in habitat distributions are controlled, consistencies in species’ responses to landscape structure emerge. Second, we present a detailed example providing step-by-step methods for application of a species-centered approach using freely available land-cover data and recent statistical modeling approaches. Third, we discuss pitfalls in current applications of the approach and recommend avenues for future developments. We conclude that the species-centered approach offers considerable promise as a means to test whether sensitivity to habitat loss and fragmentation is mediated by phylogenetic, ecological, and life-history traits. Cross-species generalities in responses to habitat loss and fragmentation will be challenging to uncover unless landscape mosaics are defined using models that reflect differing species-specific distributions, functional connectivity, and domains of scale. The emergence of such generalities would not only enhance scientific understanding of biotic processes driving fragmentation effects, but would allow managers to estimate species sensitivities in new regions.
Technical Report
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This Technical Memorandum is part of a series of three reports that provide a quantitative spatial and temporal characterization of marine biological communities associated with marine protected areas in the U.S. Caribbean. This work was conducted as part of NOAA’s Coral Reef Conservation Program (CRCP) Caribbean Coral Reef Ecosystem Monitoring (CREM) project; a partnership effort between NOAA’s National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment Biogeography Branch (CCMA-BB), U.S. Virgin Islands Department of Planning and Natural Resources – Division of Fish and Wildlife, U.S. Geological Survey (USGS), National Park Service (NPS), the University of the Virgin Islands (UVI), and the University of Hawaii (UH). The integration of NOAA/NPS led efforts with data generated by VI-DPNR provide spatial and temporal patterns in fish and benthic communities to characterize St. John coral reef ecosystems. The data and analyses in this report are intended to provide essential baseline biological information to support management decision making. This project was funded by CRCP, NOAA’s NCCOS, and the NPS Natural Resource Preservation Program (NRPP) at Virgin Islands National Park (VIIS) and NPS’s South Florida/Caribbean Inventory and Monitoring Program (SFCN).
Chapter
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Coral reef ecosystems exhibit biotic complexity and spatial heterogeneity in physical structure at multiple spatial scales. The recent application of technology to coral reef ecosystems has vastly improved the mapping and quantification of these physically complex ecological systems. Understanding the geomorphology of coral reefs, from a three-dimensional perspective, using LiDAR, offers great potential to advance our knowledge of the functional linkages between geomorphic structure and ecological processes in the marine environment. The recent application of LiDAR in coral reef ecosystems also demonstrates the depth and breadth of the potential for this technology to support research and mapping efforts in the coastal zone. This chapter builds upon the previous one, which covered the background and principles of LiDAR altimetry, by reviewing coral reef LiDAR applications and providing several case studies that highlight theutility of this technology. The application of LiDAR for navigational charting, engineering, benthic habitat mapping, ecological modeling, marine geology and environmental change detection are presented. The future directions of LiDAR applications are considered in the conclusion of this chapter, as well as the next steps for expanding the use of this remote sensing technology in coral reef environments.
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Seascape ecology studies indicate that the spatial arrangement of habitat types and the topographic complexity of the seascape are major environmental drivers of fish distributions and diversity across coral reef ecosystems. Impairment of one component of an ecologically functional habitat mosaic and reduction in the architectural complexity of coral reefs is likely to lower the quality of habitat for many fish including important fished species. Documented declines in coral cover and topographic complexity are reported from a decade of long-term coral reef ecosystem monitoring in SW Puerto Rico. To examine broader scale impacts we use “reef flattening scenarios” and spatial predictive modeling to demonstrate how declining seascape complexity will lead to contractions and fragmentation in the local spatial distribution of fish. This change may result in impaired connectivity, cascading impacts to ecological functioning and reduced resilience to environmental stressors. We propose that a shift in perspective is needed towards a more holistic and spatially-explicit seascape approach to ecosystem-based management that can help monitor structural change, predict ecological consequences, guide targeted restoration efforts and inform spatial prioritization in marine spatial planning.
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Live corals are the key habitat forming organisms on coral reefs, contributing to both biological and physical structure. Understanding the importance of corals for reef fishes is, however, restricted to a few key families of fishes, whereas it is likely that a vast number of fish species will be adversely affected by the loss of live corals. This study used data from published literature together with independent field based surveys to quantify the range of reef fish species that use live coral habitats. A total of 320 species from 39 families use live coral habitats, accounting for approximately 8 % of all reef fishes. Many of the fishes reported to use live corals are from the families Pomacentridae (68 spp.) and Gobiidae (44 spp.) and most (66 %) are either planktivores or omnivores. 126 species of fish associate with corals as juveniles, although many of these fishes have no apparent affiliation with coral as adults, suggesting an ontogenetic shift in coral reliance. Collectively, reef fishes have been reported to use at least 93 species of coral, mainly from the genus Acropora and Porities and associate predominantly with branching growth forms. Some fish associate with a single coral species, whilst others can be found on more than 20 different species of coral indicating there is considerable variation in habitat specialisation among coral associated fish species. The large number of fishes that rely on coral highlights that habitat degradation and coral loss will have significant consequences for biodiversity and productivity of reef fish assemblages.
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We present two years of experimental and descriptive data which support the hypothesis that fireweed aphids (Aphis varians) compete with intra-and interspecific aphid neighbors for the services of ant mutualists (Formica fusca and F. cinerea). Specifically, we have shown that ants are a Limited and Limiting resource for a tended aphid species. First, the presence of heavily aphid-infested fireweed shoots significantly reduced the number of ants tending neighboring conspecific populations on fireweed. Second, the presence of ant-tended aphids (Cinara sp.) on Engelmann spruce significantly reduced the number of ants tending neighboring aphid populations on fireweed. Third, the number of ants, and not just the presence of ants, had a significant effect on the fitness of fireweed aphids. Aphid populations tended by three or more F. cinerea exhibited significantly higher probabilities of persisting and growing through time than colonies tended by one or two ants. Aphid populations tended by F. fusca had a significantly higher probability of growing when tended by three or more ants only if they had declined in size during the previous week.
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The majority of fish studies on coral reefs consider only non-cryptic species and, despite their functional impor-tance, data on cryptic species are scarce. This study investi-gates inter-habitat variation in Caribbean cryptobenthic fishes by re-analysing a comprehensive data set from 58 rotenone stations around Buck Island, U.S. Virgin Islands. Boosted regression trees were used to associate the density and diver-sity of non-piscivorous cryptobenthic fishes, both in the entire data set and on reef habitats alone, with 14 abiotic and biotic variables. The study also models the habitat requirements of the three commonest species. Dead coral cover was the first or second most important variable in six of the eight models constructed. For example, within the entire data set, the number of species and total fish density increased approxi-mately linearly with increasing dead coral cover. Dead coral was also important in multivariate analyses that discriminated 10 assemblages within the entire data set. On reef habitats, the number of species and total fish density increased dramatically when dead coral exceeded *55 %. Live coral cover was typically less important for explaining variance in fish assemblages than dead coral, but live corals were important for maintaining high fish diversity. Coral species favoured by cryptobenthic species may be particularly susceptible to mortality, but dead coral may also provide abundant food and shelter for many fishes. Piscivore density was a key variable in the final models, but typically increased with increasing cryptobenthic fish diversity and abundance, suggesting both groups of fishes are responding to the same habitat variables. The density of territorial damselfishes reduced the number of cryptobenthic fish species on reef habitats. Finally, habitats delineated by standard remote sensing techniques supported distinct cryptobenthic fish assemblages, suggesting that such maps can be used as surrogates of general patterns of cryptic fish biodiversity in conservation planning.
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Many of the most abundant fish species using mangroves in the Caribbean also use other habitat types through daily home range movements and ontogenetic habitat shifts. Few studies, however, have considered the structure of the surrounding seascape when explaining the spatial distribution of fish within mangroves. This study develops an exploratory seascape approach using the geographical location of mangroves and the structure of the surrounding seascape at multiple spatial scales to explain the spatial patterns in fish density and number of species observed within mangroves of SW Puerto Rico. Seascape structure immediately surrounding mangroves was most influential in determining assemblage attributes and the density of juvenile Haemulon flavolineatum, which were significantly higher in mangroves with high seagrass cover (>40%) in close proximity (< 100 m) than mangroves with low (<40%) or no adjacent seagrasses. Highest mean density of juvenile Ocyurus chrysurus was found in offshore mangroves, with high seagrass and coral reef cover >40 and >15%, respectively) in close proximity (<100 m). In contrast, juvenile Lutjanus griseus responded at much broader spatial scales, and with highest density found in extensive onshore mangroves with a large proportion (> 40%) of seagrass within 600 m of the mangrove edge. We argue that there is an urgent need to incorporate information on the influence of seascape structure into a wide range of marine resource management activities, such as the identification and evaluation of critical or essential fish habitat, the placement of marine protected areas and the design of habitat restoration projects.
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Many parrotfishes (Scaridae) co-occur in mixed-species aggregations as juveniles, but diverge in resource use and social structure as adults. Focal observations of 3 juvenile parrotfishes (Scarus coeruleus, Sparisoma aurofrenatum, Sparisoma viride) were conducted on inshore patch reefs in the Florida Keys to examine feeding rates, food type, habitat use, and aggressive interactions. All species overlapped extensively in their use of space and food. Home ranges physically overlapped, and the proportion of microhabitats present within home ranges was similar for all species. Home range size increased with body size for S. coeruleus and S. aurofrenatum. Diets of all species were extremely similar. All fed selectively from the available foods and fed primarily (>50% total bites) on the calcareous macroalga Halimeda opuntia despite its potentially high energetic costs of procurement, low food value, and predicted avoidance. Focal individuals interacted aggressively with conspecifics, other juvenile parrotfishes, damselfishes, and occasionally grunts and wrasses. S. aurofrenatum and S. viride were most aggressive toward conspecifics. Aggressive interactions with adult parrotfishes were rare. Both Sparisoma spp. were chased more often by damselfishes than any other species. These findings support the growing body of evidence that herbivorous fish do not feed randomly from all potential foods. The aggressive interactions observed among juvenile parrotfishes are likely affecting their use of resources and may act as a precursor to subsequent territoriality as adults.
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Coral reef ecosystems are topographically complex environments and this structural heterogeneity influences the distribution, abundance and behavior of marine organisms. Airborne hydrographic lidar (Light Detection and Ranging) provides high resolution digital bathymetry from which topographic complexity can be quantified at multiple spatial scales. To assess the utility of lidar data as a predictor of fish and coral diversity and abundance, seven different morphometrics were applied to a 4 m resolution bathymetry grid and then quantified at multiple spatial scales (i.e., 15, 25, 50, 100, 200 and 300 m radii) using a circular moving window analysis. Predictive models for nineteen fish metrics and two coral metrics were developed using the new statistical learning technique of stochastic gradient boosting applied to regression trees. Predictive models explained 72% of the variance in herbivore biomass, 68% of parrotfish biomass, 65% of coral species richness and 64% of fish species richness. Slope of the slope (a measure of the magnitude of slope change) at relatively local spatial scales (15-100 m radii) emerged as the single best predictor. Herbivorous fish responded to topographic complexity at spatial scales of 15 and 25 m radii, whereas broader spatial scales of between 25 and 300 m radii were relevant for piscivorous fish. This study demonstrates great utility for lidar-derived bathymetry in the future development of benthic habitat maps and faunal distribution maps to support ecosystem based management and marine spatial planning.
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Aquatic resource managers are continually faced with construction or site development proposals which, if allowed to proceed, would ultimately alter the physical structure and cover of fish habitat. In the absence of clear quantitative guidelines linking the change in habitat to fish, resource managers often use the change in habitat area as a basis for decisions. To assess the weight of scientific evidence in support of management decisions, we summarized both the observational and experimental freshwater fish-habitat literature. We then extracted data from experimental studies (where possible) for inclusion in a meta-analysis, to provide a more rigorous assessment of the published results of experimental habitat manipulations. We found relatively strong and consistent correlational evidence linking fish and physical habitat features, yet inconsistent evidence when narratively reviewing the experimental literature. On the whole, decreases in structural habitat complexity are detrimental to fish diversity and can change species composition. Increases in structural complexity showed increases, decreases, or no measurable changes in species and (or) communities. The majority of our meta-analyses resulted in supporting a direct link between habitat and fish abundance or biomass, with fish biomass responding most strongly to habitat change. Habitat alterations are most likely to affect individual species or community structure, and thus evaluating the extent of the effect on a biological basis depends on management objectives.
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The importance of structural complexity in coral reefs has come to the fore with the global degradation of reef condition; however, the limited scale and replication of many studies have restricted our understanding of the role of complexity in the ecosystem. We qualitatively and quantitatively (where sufficient standardised data were available) assess the literature regarding the role of structural complexity in coral reef ecosystems. A rapidly increasing number of publications have studied the role of complexity in reef ecosystems over the past four decades, with a concomitant increase in the diversity of methods used to quantify structure. Quantitative analyses of existing data indicate a strong negative relationship between structural complexity and algal cover, which may reflect the important role complexity plays in enhancing herbivory by reef fishes. The cover of total live coral and branching coral was positively correlated with structural complexity. These habitat attributes may be creating much of the structure, resulting in a collinear relationship; however, there is also evidence of enhanced coral recovery from disturbances where structural complexity is high. Urchin densities were negatively correlated with structural complexity; a relationship that may be driven by urchins eroding reef structure or by their gregarious behaviour when in open space. There was a strong positive relationship between structural complexity and fish density and biomass, likely mediated through density-dependent competition and refuge from predation. More variable responses were found when assessing individual fish families, with all families examined displaying a positive relationship to structural complexity, but only half of these relationships were significant. Although only corroborated with qualitative data, structural complexity also seems to have a positive effect on two ecosystem services: tourism and shoreline protection. Clearly, structural complexity is an integral component of coral reef ecosystems, and it should be incorporated into monitoring programs and management objectives.
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Fishes are the most diverse group of vertebrates, play key functional roles in aquatic ecosystems, and provide protein for a billion people, especially in the developing world. Those functions are compromised by mounting pressures on marine biodiversity and ecosystems. Because of its economic and food value, fish biomass production provides an unusually direct link from biodiversity to critical ecosystem services. We used the Reef Life Survey’s global database of 4,556 standardized fish surveys to test the importance of biodiversity to fish production relative to 25 environmental drivers. Temperature, biodiversity, and human influence together explained 47% of the global variation in reef fish biomass among sites. Fish species richness and functional diversity were among the strongest predictors of fish biomass, particularly for the large-bodied species and carnivores preferred by fishers, and these biodiversity effects were robust to potentially confounding influences of sample abundance, scale, and environmental correlations. Warmer temperatures increased biomass directly, presumably by raising metabolism, and indirectly by increasing diversity, whereas temperature variability reduced biomass. Importantly, diversity and climate interact, with biomass of diverse communities less affected by rising and variable temperatures than species-poor communities. Biodiversity thus buffers global fish biomass from climate change, and conservation of marine biodiversity can stabilize fish production in a changing ocean.
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The previous chapters have been concerned with predicting the values of one or more outputs or response variables Y = (Y 1,..., Y m ) for a given set of input or predictor variables X = (X 1,..., X P ). Denote by x i = (x i1,..., x ip ) the inputs for the ith training case, and let y i be a response measurement. The predictions are based on the training sample (x 1, y 1),..., (x N , y N ) of previously solved cases, where the joint values of all of the variables are known. This is called supervised learning or “learning with a teacher.” Under this metaphor the “student” presents an answer ŷ i for each x i in the training sample, and the supervisor or “teacher” provides either the correct answer and/or an error associated with the student’s answer. This is usually characterized by some loss function L(y, ŷ), for example, L(y, ŷ) = (y − ŷ)2.
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Coastal marine and estuarine ecosystems are highly productive and serve a nursery function for important fisheries species. They also suffer some of the highest rates of degradation from human impacts of any ecosystems. Identifying and valuing nursery habitats is a critical part of their conservation, but current assessment practices typically take a static approach by considering habitats as individual and homogeneous entities. Here, we review current definitions of nursery habitat and propose a novel approach for assigning nursery areas for mobile fauna that incorporates critical ecological habitat linkages. We introduce the term ‘seascape nurseries’, which conceptualizes a nursery as a spatially explicit seascape consisting of multiple mosaics of habitat patches that are functionally connected. Hotspots of animal abundances/productivity identify the core area of a habitat mosaic, which is spatially constrained by the home ranges of its occupants. Migration pathways connecting such hotspots at larger spatial and temporal scales, through ontogenetic habitat shifts or inshore–offshore migrations, should be identified and incorporated. The proposed approach provides a realistic step forward in the identification and management of critical coastal areas, especially in situations where large habitat units or entire water bodies cannot be protected as a whole due to socio-economic, practical or other considerations.
Article
The foraging-time patterns of the sexes were examined in protogynous hogfishes in the genus Bodianus (Labridae). The daily social and mating activities of males in each of these marine reef fishes are distinctly different: single males defend permanent, all-purpose territories that contain a harem of females (B. rufus; San Blas Islands, Panama), males defend temporary reproductive territories (B. diplotaenia; Gulf of California, Mexico), or males are not territorial and spawn together in groups (B. eclancheri; Galapagos Archipelago, Ecuador). Female hogfishes in all 3 species mate daily and spend relatively little time on social and mating activities. B. rufus males allocated a much smaller proportion of their time (39.7%) to foraging than did conspecific females (76.8%) . Sex change by the dominant female was initiated by removing the dominant, territorial male from his harem group. All individuals tested decreased the amount of time spent foraging and increased time allocated to social and mating activities, after they became reproductively functioning males. B. diplotaenia males also spent less time foraging (45.9%) than did conspecific females (76.5%). B. eclancheri males spent most (70.2%) of their time foraging, as did conspecific females (77.3%). Males minimize foraging time when their reproductive success depends more upon time spent in social and mating activities than upon net energy gains. The reproductive success of female hogfishes, and males that compete for mates by maximizing sperm production (B. eclancheri), appears to be limited primarily by energy available for gamete production and growth.- from Author
Article
We develop a hierarchical model of heterogeneity that provides a framework for classifying patch structure across a range of scales. Patches at lower levels in the hierarchy are more simplistic and correspond to the traditional view of patches. At levels approaching the upper bounds of the hierarchy the internal structure becomes more heterogeneous and boundaries more ambiguous. At each level in the hierarchy, patch structure will be influenced by both contrast among patches as well as the degree of aggregation of patches at lower levels in the hierarchy. We apply this model to foraging theory, but it has wider applications as in the study of habitat selection, population dynamics, and habitat fragmentation. It may also be useful in expanding the realm of landscape ecology beyond the current focus on anthropocentric scales.
Article
AimThe spatial extent (scale) at which landscape attributes are measured has a strong impact on inferred species–landscape relationships. Consequently, researchers commonly measure landscape variables at multiple scales to select one scale (the ‘scale of effect’) that yields the strongest species–landscape relationship. Scales of effect observed in multiscale studies may not be true scales of effect if scales are arbitrarily selected and/or are too narrow in range. Miscalculation of the scale of effect may explain why the theoretical relationship between scale of effect and species traits, e.g. dispersal distance, is not empirically well supported.LocationWorld-wide.Methods Using data from 583 species in 71 studies we conducted a quantitative review of multiscale studies to evaluate whether research has been conducted at the true scale of effect.ResultsMultiple lines of evidence indicated that multiscale studies are often conducted at suboptimal scales. We did not find convincing evidence of a relationship between observed scale of effect and any of 29 species traits. Instead, observed scales of effect were strongly positively predicted by the smallest and largest scales evaluated by researchers. Only 29% of studies reported biological reasons for the scales evaluated. Scales tended to be narrow in range (the mean range is 0.9 orders of magnitude) and few (the mean number of scales evaluated is four). Many species (44%) had observed scales of effect equal to the smallest or largest scale evaluated, suggesting a better scale was outside that range. Increasing the range of scales evaluated decreased the proportion of species with scales of effect equal to the smallest or largest scale evaluated.Main conclusionsTo ensure that species–landscape relationships are well estimated, we recommend that the scales at which landscape variables are measured range widely, from the size of a single territory to well above the average dispersal distance.
Book
From the reviews of the First Edition."An interesting, useful, and well-written book on logistic regression models . . . Hosmer and Lemeshow have used very little mathematics, have presented difficult concepts heuristically and through illustrative examples, and have included references."—Choice"Well written, clearly organized, and comprehensive . . . the authors carefully walk the reader through the estimation of interpretation of coefficients from a wide variety of logistic regression models . . . their careful explication of the quantitative re-expression of coefficients from these various models is excellent."—Contemporary Sociology"An extremely well-written book that will certainly prove an invaluable acquisition to the practicing statistician who finds other literature on analysis of discrete data hard to follow or heavily theoretical."—The StatisticianIn this revised and updated edition of their popular book, David Hosmer and Stanley Lemeshow continue to provide an amazingly accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets. Hosmer and Lemeshow extend the discussion from biostatistics and epidemiology to cutting-edge applications in data mining and machine learning, guiding readers step-by-step through the use of modeling techniques for dichotomous data in diverse fields. Ample new topics and expanded discussions of existing material are accompanied by a wealth of real-world examples-with extensive data sets available over the Internet.
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Spatial analyses are indispensable analytical tools in biogeography and macroecology. In a recent Guest Editorial, Hawkins (Journal of Biogeography, 2012,39, 1-9) raised several issues related to spatial analyses. While we concur with some points, we here clarify those confounding (1) spatial trends and spatial autocorrelation, and (2) spatial autocorrelation in the response variable and in the residuals. We argue that recognizing spatial autocorrelation in statistical modelling is not only a crucial step in model diagnostics, but that disregarding it is essentially wrong.
Article
Coastal marine and estuarine ecosystems are highly productive and serve a nursery function for important fisheries species. They also suffer some of the highest rates of degradation from human impacts of any ecosystems. Identifying and valuing nursery habitats is a critical part of their conservation, but current assessment practices typically take a static approach by considering habitats as individual and homogeneous entities. Here, we review current definitions of nursery habitat and propose a novel approach for assigning nursery areas for mobile fauna that incorporates critical ecological habitat linkages. We introduce the term ‘seascape nurseries’, which conceptualizes a nursery as a spatially explicit seascape consisting of multiple mosaics of habitat patches that are functionally connected. Hotspots of animal abundances/productivity identify the core area of a habitat mosaic, which is spatially constrained by the home ranges of its occupants. Migration pathways connecting such hotspots at larger spatial and temporal scales, through ontogenetic habitat shifts or inshore–offshore migrations, should be identified and incorporated. The proposed approach provides a realistic step forward in the identification and management of critical coastal areas, especially in situations where large habitat units or entire water bodies cannot be protected as a whole due to socio-economic, practical or other considerations.
Article
A third-generation numerical wave model to compute random, short-crested waves in coastal regions with shallow water and ambient currents (Simulating Waves Nearshore (SWAN)) has been developed, implemented, and validated. The model is based on a Eulerian formulation of the discrete spectral balance of action density that accounts for refractive propagation over arbitrary bathymetry and current fields. It is driven by boundary conditions and local winds. As in other third-generation wave models, the processes of wind generation, whitecapping, quadruplet wave-wave interactions, and bottom dissipation are represented explicitly. In SWAN, triad wave-wave interactions and depth-induced wave breaking are added. In contrast to other third-generation wave models, the numerical propagation scheme is implicit, which implies that the computations are more economic in shallow water. The model results agree well with analytical solutions, laboratory observations, and (generalized) field observations.