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Remote coral reefs are thought to be more resilient to climate change due to their isolation from local stressors like fishing and pollution. We tested this hypothesis by measuring the relationship between local human influence and coral community resilience. Surprisingly, we found no relationship between human influence and resistance to disturbance and some evidence that areas with greater human development may recover from disturbance faster than their more isolated counterparts. Our results suggest remote coral reefs are imperiled by climate change, like so many other geographically isolated ecosystems, and are unlikely to serve as effective biodiversity arks. Only drastic and rapid cuts in greenhouse gas emissions will ensure coral survival. Our results also indicate that some reefs close to large human populations were relatively resilient. Focusing research and conservation resources on these more accessible locations has the potential to provide new insights and maximize conservation outcomes.

Coral reefs worldwide are facing impacts from climate change, overfishing, habitat destruction, and pollution. The cumulative effect of these impacts on global capacity of coral reefs to provide ecosystem services is unknown. Here, we evaluate global changes in extent of coral reef habitat, coral reef fishery catches and effort, Indigenous consumption of coral reef fishes, and coral-reef-associated biodiversity. Global coverage of living coral has declined by half since the 1950s. Catches of coral-reef-associated fishes peaked in 2002 and are in decline despite increasing fishing effort, and catch-per-unit effort has decreased by 60% since 1950. At least 63% of coral-reef-associated biodiversity has declined with loss of coral extent. With projected continued degradation of coral reefs and associated loss of biodiversity and fisheries catches, the well-being and sustainable coastal development of human communities that depend on coral reef ecosystem services are threatened.

The responses of ectothermic organisms to changes in temperature can be modified by acclimatization or adaptation to local thermal conditions. Thus, the effect of global warming and the deleterious effects of extreme heating events (e.g., heatwaves) on the metabolism and fitness of ectotherms can be population specific and reduced at warmer sites. We tested the hypothesis that when environmental temperature is greater, grazer populations in the Galápagos are less thermally sensitive (potentially due to acclimatization or adaptation). We quantified the acute thermal sensitivity of four populations of the pencil sea urchin, Eucidaris galapagensis, by measuring individual oxygen consumption across a range of temperatures. Thermal performance curves were estimated for each population and compared to local thermal conditions 2 months prior to collection. Results indicate that E. galapagensis populations were adapted and/or acclimatized to short-term local temperature as populations at warmer sites had substantially higher thermal tolerances. The acute thermal optimum (Topt) for the warmest and coolest site populations differed by 3 °C and the Topt was positively correlated with maximum temperature recorded at each site. Additionally, temperature-normalized respiration rate and activation energy (E) were negatively related to the maximum temperature. Understanding the temperature-dependent performance of the pencil urchin (the most significant mesograzer in this system), including its population specificity, provides insight into how herbivores and the functions they perform might be affected by further ocean heating.

Seafood mislabeling occurs in a wide range of seafood products worldwide, resulting in public distrust, economic fraud, and health risks for consumers. We quantified the extent of shrimp mislabeling in coastal and inland North Carolina. We used standard DNA barcoding procedures to determine the species identity of 106 shrimp sold as “local” by 60 vendors across North Carolina. Thirty-four percent of the purchased shrimp was mislabeled, and surprisingly the percentage did not differ significantly between coastal and inland counties. One third of product incorrectly marketed as “local” was in fact whiteleg shrimp: an imported and globally farmed species native to the eastern Pacific, not found in North Carolina waters. In addition to the negative ecosystem consequences of shrimp farming (e.g., the loss of mangrove forests and the coastal buffering they provide), North Carolina fishers—as with local fishers elsewhere—are negatively impacted when vendors label farmed, frozen, and imported shrimp as local, fresh, and wild-caught.

Seafood mislabeling is a widely documented problem that has significant implications for human and environmental health. Defined as when seafood is sold under something other than its true species name, seafood fraud allows less-desired or illegally caught species to be marketed as one recognizable to consumers. Red snapper is one of the most frequently mislabeled species, with previous studies showing mislabeling rates as high as 77%. We assessed whether red snapper mislabeling rates varied among states or vendor type. We also determined the IUCN Red List designation of substituted species to assess whether frequently substituted stocks were more or less at-risk than red snapper stocks. We used standard DNA barcoding protocols to determine the identity of products labeled as “red snapper” from sushi restaurants, seafood markets, and grocery stores in the Southeastern United States. Overall, 72.6% of samples (out of 62) were mislabeled, with sushi restaurants mislabeling samples 100% of the time. Out of 13 substituted species (including samples that were indistinguishable between two species), seven (53.8%) were not native to the United States of the 12 substituted species assessed by the IUCN Red List, 11 (91.6%) were listed as less threatened than red snapper. These results contribute to a growing body of mislabeling research that can be used by government agencies trying to develop effective policies to combat seafood fraud and consumers hoping to avoid mislabeled products.

Ecology is a young discipline that needs to develop into a predictive science to confront the challenges of human population pressures and habitat degradation. Basic ecology has disproportionately focused on undisturbed, charismatic ecosystems, species and academic questions, leaving gaps in its ability to inform the conservation and management of degraded, threatened ecosystems. Foundation species-dependent organisms have been studied at the expense of the habitat-forming species that build and maintain communities. We used cobble beaches as a model system to discuss the consequences of this disparity on translational ecology. We suggest that the historic development of ecology has led to an academic discipline ill-suited for proactive conservation. We propose that the incorporation of foundation species and a hierarchical organization theory, into the conceptual framework of ecology, will improve its predictive ability and successful application in conservation and the restoration of degraded ecosystems.

Scientists have advocated for local interventions, such as creating marine protected areas and implementing fishery restrictions, as ways to mitigate local stressors to limit the effects of climate change on reef-building corals. However, in a literature review, we find little empirical support for the notion of managed resilience. We outline some reasons for why marine protected areas and the protection of herbivorous fish (especially parrotfish) have had little effect on coral resilience. One key explanation is that the impacts of local stressors (e.g., pollution and fishing) are often swamped by the much greater effect of ocean warming on corals. Another is the sheer complexity (including numerous context dependencies) of the five cascading links assumed by the managed-resilience hypothesis. If reefs cannot be saved by local actions alone, then it is time to face reef degradation head-on, by directly addressing anthropogenic climate change - the root cause of global coral decline.

Temperature drives biological responses that scale from the cellular to ecosystem levels and thermal sensitivity will shape organismal functions and population dynamics as the world warms. Reef-building corals are sensitive to temperature due to their endosymbiotic relationship with single-celled dinoflagellates, with mass mortality events increasing in frequency and magnitude. The purpose of this study was to quantify the thermal sensitivity of important physiological functions of a Caribbean reef-building coral, Orbicella franksi, through the measurement of thermal performance curves (TPCs). We compared TPC metrics (thermal optimum, critical maximum, activation energy, deactivation energy, and rate at a standardized temperature) between two populations at the northern and southern extents of the geographic range of O. franksi. We further compared essential coral organismal processes (gross photosynthesis, respiration, and calcification) within a site to determine which function is most sensitive to thermal stress using a hierarchical Bayesian-modeling approach. We found evidence for differences in thermal performance, which could be due to thermal adaptation or acclimatization, with higher TPC metrics (thermal optimum and critical maximum) in warmer Panama, compared to cooler Bermuda. We also documented the hierarchy in thermal sensitivity of essential organismal functions within a population: respiration was less sensitive than photosynthesis, which was less sensitive than calcification. Understanding thermal performance of corals is essential for projecting coral reef futures, given that key biological functions necessary to sustain coral reef ecosystems are thermally mediated.

Coral reefs are important habitats that represent global marine biodiversity hotspots and provide important benefits to people in many tropical regions. However, coral reefs are becoming increasingly threatened by climate change, overfishing, habitat destruction, and pollution. Historical baselines of coral cover are important to understand how much coral cover has been lost, e.g., to avoid the 'shifting baseline syndrome'. There are few quantitative observations of coral reef cover prior to the industrial revolution, and therefore baselines of coral reef cover are difficult to estimate. Here, we use expert and ocean-user opinion surveys to estimate baselines of global coral reef cover. The overall mean estimated baseline coral cover was 59% (±19% standard deviation), compared to an average of 58% (±18% standard deviation) estimated by professional scientists. We did not find evidence of the shifting baseline syndrome, whereby respondents who first observed coral reefs more recently report lower estimates of baseline coral cover. These estimates of historical coral reef baseline cover are important for scientists, policy makers, and managers to understand the extent to which coral reefs have become depleted and to set appropriate recovery targets.

The United States has been at the forefront of marine resource stewardship since the 1970s when Federal officials began to implement a series of national policies aimed at the conservation and management of public trust resources in the ocean. Beginning with the establishment of the National Oceanic and Atmospheric Administration in 1970, soon followed by several pieces of landmark legislation, this era marked the start of a continuing effort to integrate ecosystem science with marine resource management. Among the most important bipartisan legacies of this effort has been the steady expansion of marine managed areas in U.S. coastal and ocean waters. This legacy is being challenged as the Trump Administration considers whether to alter or eliminate the nation's Marine National Monuments and National Marine Sanctuaries.

Marine protected areas (MPAs) are a primary management tool for mitigating threats to marine biodiversity 1,2 . MPAs and the species they protect, however, are increasingly being impacted by climate change. Here we show that, despite local protections, the warming associated with continued business-as-usual emissions (RCP8.5) 3 will likely result in further habitat and species losses throughout low-latitude and tropical MPAs 4,5 . With continued business-as-usual emissions, mean sea-surface temperatures within MPAs are projected to increase 0.035 °C per year and warm an additional 2.8 °C by 2100. Under these conditions, the time of emergence (the year when sea-surface temperature and oxygen concentration exceed natural variability) is mid-century in 42% of 309 no-take marine reserves. Moreover, projected warming rates and the existing 'community thermal safety margin' (the inherent buffer against warming based on the thermal sensitivity of constituent species) both vary among ecoregions and with latitude. The community thermal safety margin will be exceeded by 2050 in the tropics and by 2150 for many higher latitude MPAs. Importantly, the spatial distribution of emergence is stressor-specific. Hence, rearranging MPAs to minimize exposure to one stressor could well increase exposure to another. Continued business-as-usual emissions will likely disrupt many marine ecosystems, reducing the benefits of MPAs.

Temperature can influence trophic interactions via predictable effects on the metabolism of ecothermic consumers. Under some conditions, warming should increase top-down control, and trophic transfer rates, leading to declines in prey populations. We tested this prediction in the Galápagos Islands, an equatorial upwelling region, where water temperatures are highly variable and nutrient availability is thought to control primary production and standing algal biomass. We used grazing assays, field surveys, and a herbivore exclusion experiment to test the hypothesis that grazing rate and algal biomass are, in part, regulated by temperature via the temperature-dependence of herbivory. Grazing rates were greater during the warm season for urchins and other consumers (including fishes, turtles, and iguanas). Field surveys at 10 sites over 5 years found that temperature was strongly negatively related to macroalgal cover. The results of the exclusion experiment indicate that herbivores had a large effect on macroalgal biomass, even during intense upwelling. Our results suggest that in shallow subtidal habitats across the Galápagos archipelago, grazing pressure increases with temperature, potentially resulting in reduced algal biomass when upwelling is weak and greater algal biomass when upwelling is strong and water is cold; an alternative explanation for widely observed association between upwelling intensity and algal biomass.

Native prey can be particularly vulnerable to consumption by exotic predators. Prey naiveté, the failure to recognize a novel predator due to lack of recent co-evolutionary history, likely facilitates the disproportionate impact that some exotic predators exert on prey populations. Lionfish Pterois volitans, exotic predators from the Pacific, have invaded coral reefs and other coastal habitats along the western Atlantic. Prey naiveté towards novel lionfish was tested in field experiments and with observations using closest approach distance as the anti-predator response. We quantified the distance of prey fishes to exotic lionfish in both the Atlantic and Pacific (invasive and native ranges of lionfish) as well as to native predators in the Atlantic. In the Atlantic, experiments indicated that Haemulon plumierii, prey of lionfish, generally display a closer approach distance to exotic than to native predators, and field observations of free-ranging fish revealed that at least 5 other species of small fishes (Halichoeres bivitattus, Halichoeres garnoti, Scarus taeniopterus, Stegastes leucostictus and Thalassoma bifasciatum) also might exhibit limited predatoravoidance behaviour towards invasive lionfish. We also found that 3 families of small fish (Labridae, Pomacentridae and Scaridae) maintained greater distances from lionfish in the Pacific compared with the Atlantic in both experimental and field observations. These results suggest prey naiveté to exotic lionfish by at least 8 species of fish (Abudefduf saxatilis, H. plumierii, H. bivitattus, H. garnoti, S. taeniopterus, Sparisoma aurofrenatum, S. leucostictus and T. bifasciatum) in the Atlantic, which could be contributing to the rapid expansion of this invasive species by enhancing its fitness and reproductive output through high predation efficiency.

Viewing facilitation through the lens of the niche concept is one way to unify conceptual and empirical advances about the role of facilitation in community ecology. We clarify conceptually and through examples from marine and terrestrial environments how facilitation can expand species' niches and consider how these interactions can be scaled up to understand the importance of facilitation in setting a species' geographic range. We then integrate the niche-broadening influence of facilitation into current conceptual areas in ecology, including climate change, diversity maintenance and the relationship between diversity and ecosystem functioning. Because facilitation can influence the range of physical conditions under which a species can persist, it has the potential to mitigate the effects of climate change on species distributions. Whereas facilitation has mostly been considered as a diversity-promoting interaction by ameliorating abiotic stresses, if facilitated species' niches expand and become less distinct as a result of habitat amelioration, the forces that maintain diversity and promote coexistence in regions or habitats dominated by the facilitator could be reduced (i.e. the sign of the effects of facilitation on populations could be species-specific). Finally, shifting or broadening ecological niches could alter the relationship between diversity and ecosystem functioning. A niche-based perspective on the effects of facilitation can foster a greater mechanistic understanding of the role played by facilitation in regulating species coexistence, range shifts and ecosystem functioning in a changing world.

Temperature imposes a constraint on the rates and outcomes of ecological processes that determine community- and ecosystem-level patterns. The application of metabolic scaling theory has advanced our understanding of the influence of temperature on pattern and process in marine communities. Metabolic scaling theory uses the fundamental and ubiquitous patterns of temperature-dependent metabolism to predict how environmental temperature influences patterns and processes at higher levels of biological organization. Here, we outline some of these predictions to review recent advances and illustrate how scaling theory might be applied to new challenges. For example, warming can alter species interactions and food-web structure and can also reduce total animal biomass supportable by a given amount of primary production by increasing animal metabolism and energetic demand. Additionally, within a species, larval development is faster in warmer water, potentially influencing dispersal and other demographic processes like population connectivity and gene flow. These predictions can be extended further to address major questions in marine ecology, and present an opportunity for conceptual unification of marine ecological research across levels of biological organization. Drawing on work by ecologists and oceanographers over the last century, a metabolic scaling approach represents a promising way forward for applying ecological understanding to basic questions as well as conservation challenges.

Although the independent effects of propagule supply and resource availability on species diversity are widely recognized, there are conflicting predictions of how resource availability affects the strength of propagule supply. To determine how propagule supply and resource availability interact to control species richness, we compared the effects of grazer propagule additions on grazer and algal assemblages across an experimental gradient of algal productivity. Different levels of algal productivity (i.e., replacement rate of grazers' food resource) were maintained by manipulating light. Despite light-driven changes in algal standing biomass and diversity, algal resource availability had no effect on propagule limitation of grazer species richness, nor on grazer community composition. Instead, augmenting grazer propagule supply had equally strong, positive effects on grazer richness at all levels of algal resource availability. Although there was evidence for competition and resource limitation in the high propagule supply/low resource treatment, competition was evidently too weak or the experimental duration was too short to lead to competitive exclusion and changes in species richness, evenness, and composition. Our results highlight potential differences in resource use between sessile producers and mobile grazers. Unlike plants that consume inorganic nutrients and light whose renewal is positive, donor-controlled, and identity-fixed, animals consume dynamic resources that can respond to consumption by increasing growth rates, or going extinct and being replaced by other species, as we observed in the replacement of easily ingested green algae by less preferred red algae. The dual nature of these dynamic resources may consequently weaken the link between resource renewal rates and propagule limitation in animal communities.

Overfishing of herbivorous fishes is one of the primary causes of Caribbean coral reef decline. In Belize, herbivorous fishes comprised 28% of the catch from 2005 to 2008. In 2009, the Belize Fisheries Department implemented a national ban on herbivorous fish harvesting to mitigate high-macroalgal cover on much of the Belize Barrier Reef. However, compliance with this approach has not been evaluated. We assessed the proportion of herbivorous fish in local markets by genetically identifying fish fillets sold in five major towns in Belize from 2009 to 2011. We found that 5-7% of 111 fillets were identified as herbivorous fish and 32-51% were mislabeled. A 5-7% proportion of parrotfish in local markets suggests some ongoing parrotfish harvesting. However, our results suggest that the ban has reduced herbivorous fish harvesting and has the potential to help facilitate the restoration of coral reef ecosystems.

Aim: We lack a robust understanding of whether exotic species, in addition to causing changes immediately after establishing, might continue to increase in dominance long after invasion events occur. To address this, we resurveyed strandline plant communities, which are likely to have been invaded for over two centuries. Location: Northeastern USA. Methods: We resurveyed the richness and cover of native and exotic plants in 2008 and 2009 at 18 sites, which had originally been surveyed in 1998. We examined whether native and exotic dominance had changed, whether native-rich sites were less likely to be impacted by exotics over time, whether changes in dominance were driven by large changes in a small number of outlier species or by small, incremental changes among many species and whether disturbance mediated any of these relationships. Results: Exotic dominance increased across sites. Initial native diversity was unrelated to patterns of exotic dominance during resurveys. The identity of species that were outliers with respect to changes in distribution or cover varied between resurvey years. Significant changes in exotic-to-native richness ratios at sites were detectible with or without the inclusion of outlier species, but changes in abundance ratios were only significant when outlier species were included. Disturbance across sites was not correlated with species richness, cover, or changes in dominance. Main conclusions: In this historically invaded community, exotics have increased in dominance over the last decade. This change is not due solely to the success of a few hyper-dominant species, but also to the cumulative effect of small changes in distribution among many species. It remains unclear whether patterns observed are due to invasion processes that are playing out very slowly through time or to some other explanation. Our findings highlight the need for a more robust understanding of the long-term dynamics of species invasions.

Many marine scientists have concluded that coral reefs are moving toward or are locked into a seaweed-dominated state. However, because there have been no regional- or global-scale analyses of such coral reef "phase shifts," the magnitude of this phenomenon was unknown. We analyzed 3581 quantitative surveys of 1851 reefs performed between 1996 and 2006 to determine the frequency, geographical extent, and degree of macroalgal dominance of coral reefs and of coral to macroalgal phase shifts around the world. Our results indicate that the replacement of corals by macroalgae as the dominant benthic functional group is less common and less geographically extensive than assumed. Although we found evidence of moderate local increases in macroalgal cover, particularly in the Caribbean, only 4% of reefs were dominated by macroalgae (i.e.,>50% cover). Across the Indo-Pacific, where regional averages of macroalgal cover were 9-12%, macroalgae only dominated 1% of the surveyed reefs. Between 1996 and 2006, phase shift severity decreased in the Caribbean, did not change in the Florida Keys and Indo-Pacific, and increased slightly on the Great Barrier Reef due to moderate coral loss. Coral reef ecosystems appear to be more resistant to macroalgal blooms than assumed, which has important implications for reef management.

Biodiversity may enhance productivity either because diverse communities more often contain productive species (selection effects) or because they show greater complementarity in resource use. Our understanding of how these effects influence community production comes almost entirely from studies of plants. To test whether previous results apply to higher trophic levels, we first used simulations to derive expected contributions of selection and complementarity to production in competitive assemblages defined by either neutral interactions, dominance, or a trade-off between growth and competitive ability. The three types of simulated assemblages exhibited distinct interaction signatures when diversity effects were partitioned into selection and complementarity components. We then compared these signatures to those of experimental marine communities. Diversity influenced production in fundamentally different ways in assemblages of macroalgae, characterized by growth-competition trade-offs, vs. in herbivores, characterized by dominance. Forecasting the effects of changing biodiversity in multitrophic ecosystems will require recognizing that the mechanism by which diversity influences functioning can vary among trophic levels in the same food web.

Surveys of natural habitats often indicate that native and exotic species richness are positively correlated at large scales and negatively correlated at small scales. The small-scale relationship is often presented as evidence that native richness can repel invasion or conversely that exotic invasions can reduce native diversity. The larger scale pattern has been interpreted as evidence of the importance of facilitation, variable habitat quality, propagule supply, and other ecological phenomena. However, these explanations fail to consider expected native-exotic richness relationships under a null model assuming no species interactions. We show via simulation that the null expectation for a randomly assembled community is a negative relationship between native and exotic species richness at the smallest scales and, when plots vary in total richness, a positive relationship at larger scales. We outline a procedure to compare observational data to this null expectation using a permutation test of labels of species origin (native or exotic). Our use of this technique on plant community data indicates that patterns of native and exotic richness are remarkably similar to those generated by a null model. We argue that a null model approach is needed to evaluate whether observed native-exotic richness data deviate significantly from expected patterns generated by sampling and statistical artifacts.

L'érosion hydrique est une des causes majeures de la dégradation des sols. Ce phénomène entraîne une perte de potentiel de production du sol là où il est décapé et, au-delà, des dégâts nombreux : coulées boueuses, etc. L'érosion hydrique est influencée par les façons culturales pratiquées et les aménagements qui se trouvent sur le territoire cultivé. Les façons culturales sont donc étudiées afin de limiter cette érosion hydrique sur des versants du Lauragais et des bassins versants du nord de la France. L'objectif est donc d'ébaucher une norme de production agricole anti-érosion tenant compte des gains et coûts respectifs.

In most communities, a considerable number of the constituent species will only occupy a small percentage of sites or habitat patches. However, the factors that limit the distribution and abundance of rare species are seldom examined and are poorly understood. I tested several explanations of landscape-scale rarity in the New England cobble beach plant community, an assemblage of halophytic forbs associated with fringing beds of the marine intertidal grass Spartina alterniflora. Spartina reduces flow velocity and stabilizes the cobble substrate, thereby reducing the burial of seeds and seedlings of other species. Frequencies of the presence of forb species behind 387 sampled Spartina beds distributed along 120 km of shoreline in Narragansett Bay, Rhode Island, USA, ranged from 0.005 to 0.382. Both the whole forb assemblage and individual species were strongly nested with respect to patch size and species richness. Species that were rare on a landscape scale were generally only found behind the longest beds, and bed length was positively related to species diversity. Experimental seed additions to 40 beds ranging in length from 8 to 688 m indicated that intermediate-sized beds often occupied by common species are not habitable by three rare forbs. When present behind the longest beds, these rare species are always associated with a microhabitat characterized by a relatively fine-grained and highly stable substrate. A series of substrate manipulations combined with experimental seed additions indicated that the rare annuals Spergularia marina, Salicornia biglovii, and Atriplex arenaria are restricted to the longest Spartina beds because smaller beds lack suitable substrate. These experiments also suggest that seed supply, competitors, and herbivores are not the proximate causes of the absence of these species from smaller beds, although dispersal limitation may prevent the colonization of many larger habitable patches. The microhabitat required by the rare forbs appears to be generated by the deposition of fine-grained particles behind the center of the longest Spartina beds. Consequently, bed length is causally related to the distribution of populations at a landscape scale and to species richness and composition at the scale of a whole habitat patch.

Egalement paru dans : INRA ESR Toulouse 1998 Série D ; 98-09D; National audience; Si l'érosion, due à l'eau, sur les parcelles agricoles du versant du Sud-Ouest de la France, dans le Lauragais (Midi-Pyrénées), est bien réelle et occasionne des dégâts sur les équipements collectifs et sur les cultures, elle est rarement combattue. Au contraire, les évolutions de la Politique agricole commune, la course à l'intensification agricole ont conduit à une aggravation du phénomène. En retenant alors une érosion de versant en Midi-Pyrénées que l'agriculteur seul ne peut pas traiter et qui engendre des dégâts sur le domaine public, cet article propose une analyse de la prévention sur un cas réel. Puis il présente un modèle économique qui cherche à obtenir une gestion optimale d'actions antiérosives complexes, en tenant compte de ce qu'elles apportent comme avantages et coûts aux consommateurs et à l'agriculteur qui est aidé pour cela. Les perspectives économiques que ce travail permet sont alors discutées.

Single species can have large effects on entire communities through habitat modification and facilitation. I tested the general hypothesis that the intertidal grass Spartina alterniflora facilitates the establishment and persistence of New England cobble beach plant communities by modifying the shoreline environment. This community is dominated by halophytic forbs and is restricted to estuarine cobble beaches bordered by Spartina. Beds of Spartina can reduce mean water velocity by 50% and maximum velocity by nearly an order of magnitude, and they can substantially stabilize the cobble substrate. Specifically, I determined the importance of five life history stages (seed supply, seed germination, seedling emergence, seedling establishment, and adult survival) and four factors (water velocity, substrate stability, herbivory, and soil quality) in limiting lateral plant distribution. A seed addition experiment demonstrated that seedlings could only emerge behind Spartina, suggesting that seedling emergence is the proximate life history stage limiting adult distribution. Seed germination and adult survival do not appear to be limiting stages, at least in an absolute sense. Although seed supply was much greater (~10-100 x) behind Spartina, a substantial number of seeds were caught in seed traps placed between beds, suggesting that seed supply also does not limit absolute plant distribution. These results are supported by the presence of seedlings buried below the substrate surface between beds at the time when seedlings are naturally emerging behind beds. A manipulative field experiment was performed to test the effects of substrate instability, soil quality, and herbivory on seedling emergence between beds. Seeds of two annual cobble beach species (Suaeda linearis and Salicornia europaea) were added to plots behind Spartina and also between beds with and without substrate stabilization manipulations. This treatment was designed to stabilize the substrate in a manner that would not affect water velocity and soil characteristics or prevent access by potential herbivores. When not buffered by Spartina, seedlings of both species were only able to emerge and survive when the substrate was artificially stabilized. These results indicate that Spartina alterniflora facilitates the establishment and persistence of cobble beach plant communities by stabilizing the substrate and enabling seedlings to emerge and survive.

Morphological plasticity is common among clonal organisms, including scleractinian corals, yet the role of phenotypic plasticity in coral ecology and evolution is largely unexplored. Additionally, it is unclear how much variation in plastic responses exists among individuals, populations, and species, and thus how much potential there is for natural selection to act on coral reaction norms. In the branching coral Madracis mirabilis, corallite architecture and density, branch diameter and spacing, and overall aggregate morphology all vary among environments. To examine the role of phenotypic plasticity in generating these patterns, clonal replicates of five genotypes of M. mirabilis were transplanted from each of two source populations into four treatment environments on the north coast of Jamaica. Flow rate, sedimentation, irradiance, water temperature, and salinity all varied among these environments. DNA fingerprinting was used to ensure that the 10 transplanted genotypes were genetically distinct. Six morphological traits (intersepta area, septa length, columella area, corallite area, corallite spacing, and branch tip diameter) were measured after transplantation to determine whether they were altered in response to environmental conditions. Because these traits were correlated, principal components analysis was used to define new, uncorrelated traits for analysis. Four of the five corallite traits and branch diameter were significantly affected by the environment, demonstrating that morphological variation among environments in M. mirabilis is due in large part to phenotypic plasticity. No difference was detected between the two source populations in the magnitude or direction of their plastic responses, but there was substantial variation among genotypes (genotype x environment interaction). Many of the phenotypic changes of both populations resulted in the transplants becoming morphologically similar to resident conspecifics in each treatment environment. Genotypes from both populations were able to maintain similar growth rates under diverse environmental conditions. Such morphological convergence by phenotypic plasticity may expand the ecological range of this species by enabling genotypes to tolerate spatially and temporally variable environments.

National audience

Observations along the north coast of Jamaica in 1994 suggested that areas of relatively high coral cover and high coral diversity occurred adjacent to reefs that have been in decline since 1980. This study was carried out to quantify these observations, to determine whether similar variation occurs elsewhere in the Caribbean, and to draw attention to the significance of kilometer-wide variation in coral reef community ecology. The fore reef (10 m depth) of Discovery Bay, Jamaica, had 60% macroalgae cover and appeared typical of a highly degraded Caribbean reef. However, neighboring reefs (

National audience