Morphological and Molecular Identification of Ulva spp. (Ulvophyceae; Chlorophyta) from Algarrobo Bay, Chile: Understanding the Composition of Green Tides.

Green algae blooms of the genus Ulva are occurring globally and are primarily attributed to anthropogenic factors. At Los Tubos beach in Algarrobo Bay along the central Chilean coast, there have been blooms of these algae that persist almost year-round over the past 20 years, leading to environmental, economic, and social issues that affect the local government and communities. The objective of this study was to characterize the species that form these green tides based on a combination of ecological, morpho-anatomical, and molecular information. For this purpose, seasonal surveys of beached algal fronds were conducted between 2021 and 2022. Subsequently, the sampled algae were analyzed morphologically and phylogenetically using the molecular markers ITS1 and tufA, allowing for the identification of at least five taxa. Of these five taxa, three (U. stenophylloides, U. uncialis, U. australis) have laminar, foliose, and distromatic morphology, while the other two (U. compressa, U. aragoensis) have tubular, filamentous, and monostromatic fronds. Intertidal surveys showed that U. stenophylloides showed the highest relative coverage throughout the seasons and all intertidal levels, followed by U. uncialis. Therefore, we can establish that the green tides on the coast of Algarrobo in Chile are multispecific, with differences in relative abundance during different seasons and across the intertidal zone, opening opportunities for diverse future studies, ranging from ecology to algal biotechnology.

Microbial community and network responses across strong environmental gradients: How do they compare with macroorganisms?

The way strong environmental gradients shape multispecific assemblages has allowed us to examine a suite of ecological and evolutionary hypotheses about structure, regulation and community responses to fluctuating environments. But whether the highly diverse co-occurring microorganisms are shaped in similar ways as macroscopic organisms across the same gradients has yet to be addressed in most ecosystems. Here, we characterize intertidal biofilm bacteria communities, comparing zonation at both the "species" and community levels, as well as network attributes, with co-occurring macroalgae and invertebrates in the same rocky shore system. The results revealed that the desiccation gradient has a more significant impact on smaller communities, while both desiccation and submersion gradients (surge) affect the larger, macroscopic communities. At the community level, we also confirmed the existence of distinct communities within each intertidal zone for microorganisms, similar to what has been previously described for macroorganisms. But our results indicated that dominant microbial organisms along the same environmental gradient exhibited less differentiation across tidal levels than their macroscopic counterparts. However, despite the substantial differences in richness, size and attributes of co-occurrence networks, both macro- and micro-communities respond to stress gradients, leading to the formation of similar zonation patterns in the intertidal rocky shore.

Environmental DNA reveals temporal variation in mesophotic reefs of the Humboldt upwelling ecosystems of central Chile: Toward a baseline for biodiversity monitoring of unexplored marine habitats.

Temperate mesophotic reef ecosystems (TMREs) are among the least known marine habitats. Information on their diversity and ecology is geographically and temporally scarce, especially in highly productive large upwelling ecosystems. Lack of information remains an obstacle to understanding the importance of TMREs as habitats, biodiversity reservoirs and their connections with better-studied shallow reefs. Here, we use environmental DNA (eDNA) from water samples to characterize the community composition of TMREs on the central Chilean coast, generating the first baseline for monitoring the biodiversity of these habitats. We analyzed samples from two depths (30 and 60 m) over four seasons (spring, summer, autumn, and winter) and at two locations approximately 16 km apart. We used a panel of three metabarcodes, two that target all eukaryotes (18S rRNA and mitochondrial COI) and one specifically targeting fishes (16S rRNA). All panels combined encompassed eDNA assigned to 42 phyla, 90 classes, 237 orders, and 402 families. The highest family richness was found for the phyla Arthropoda, Bacillariophyta, and Chordata. Overall, family richness was similar between depths but decreased during summer, a pattern consistent at both locations. Our results indicate that the structure (composition) of the mesophotic communities varied predominantly with seasons. We analyzed further the better-resolved fish assemblage and compared eDNA with other visual methods at the same locations and depths. We recovered eDNA from 19 genera of fish, six of these have also been observed on towed underwater videos, while 13 were unique to eDNA. We discuss the potential drivers of seasonal differences in community composition and richness. Our results suggest that eDNA can provide valuable insights for monitoring TMRE communities but highlight the necessity of completing reference DNA databases available for this region.

Emergent Spatial Patterns Can Indicate Upcoming Regime Shifts in a Realistic Model of Coral Community.

AbstractIncreased stress on coastal ecosystems, such as coral reefs, seagrasses, kelp forests, and other habitats, can make them shift toward degraded, often algae-dominated or barren communities. This has already occurred in many places around the world, calling for new approaches to identify where such regime shifts may be triggered. Theoretical work predicts that the spatial structure of habitat-forming species should exhibit changes prior to regime shifts, such as an increase in spatial autocorrelation. However, extending this theory to marine systems requires theoretical models connecting field-supported ecological mechanisms to data and spatial patterns at relevant scales. To do so, we built a spatially explicit model of subtropical coral communities based on experiments and long-term datasets from Rapa Nui (Easter Island, Chile), to test whether spatial indicators could signal upcoming regime shifts in coral communities. Spatial indicators anticipated degradation of coral communities following increases in frequency of bleaching events or coral mortality. However, they were generally unable to signal shifts that followed herbivore loss, a widespread and well-researched source of degradation, likely because herbivory, despite being critical for the maintenance of corals, had comparatively little effect on their self-organization. Informative trends were found under both equilibrium and nonequilibrium conditions but were determined by the type of direct neighbor interactions between corals, which remain relatively poorly documented. These inconsistencies show that while this approach is promising, its application to marine systems will require detailed information about the type of stressor and filling current gaps in our knowledge of interactions at play in coral communities.

Expansion of marine pollution along the coast: Negative effects on kelps and contamination transference to benthic herbivores?

Heavy metals and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants that frequently co-occur in coastal environments. These contaminants can have negative impacts on the health and stability of marine and coastal ecosystems, affecting both the organisms themselves and the humans who consume them. A coastal industrial park in central Chile, housing a coal thermal power plant and other industrial activities, contributes to such pollution of coastal waters; however, neither the spatial alongshore distribution of heavy metals and PAHs, nor an assessment of their ecological effects on the biota have been systematically documented to date. In this paper, we present evidence regarding the direct negative effect of contamination by heavy metals and PAHs on the early life stages of kelps-being extremely harmful to their population persistence near highly polluted sites-as well as the indirect effects of their transference through the food web to higher trophic levels, leading to negative consequences for the feeding intake, growth, fertility, and larval development of marine herbivores that consume the contaminated seaweed. Likewise, the dispersion of contaminants by ocean currents can exacerbate the effects of pollution, having an adverse influence on marine ecosystem health even at sites far from the pollution source. Therefore, it is necessary to investigate the distribution patterns and extent of pollution along the coast to understand the impact of heavy metals and PAHs pollution on seaweed populations and the food web. It is considered critical for the development of effective environmental policies and regulations to protect these ecosystems and the people who depend on them.

Monitoring the fabric of nature: using allometric trophic network models and observations to assess policy effects on biodiversity.

Species diversity underpins all ecosystem services that support life. Despite this recognition and the great advances in detecting biodiversity, exactly how many and which species co-occur and interact, directly or indirectly in any ecosystem is unknown. Biodiversity accounts are incomplete; taxonomically, size, habitat, mobility or rarity biased. In the ocean, the provisioning of fish, invertebrates and algae is a fundamental ecosystem service. This extracted biomass depends on a myriad of microscopic and macroscopic organisms that make up the fabric of nature and which are affected by management actions. Monitoring them all and attributing changes to management policies is daunting. Here we propose that dynamic quantitative models of species interactions can be used to link management policy and compliance with complex ecological networks. This allows managers to qualitatively identify 'interaction-indicator' species, which are highly impacted by management policies through propagation of complex ecological interactions. We ground the approach in intertidal kelp harvesting in Chile and fishers' compliance with policies. Results allow us to identify sets of species that respond to management policy and/or compliance, but which are often not included in standardized monitoring. The proposed approach aids in the design of biodiversity programmes that attempt to connect management with biodiversity change. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Spatio-temporal patterns of the crustacean demersal fishery discard from the south Humboldt Current System, based on scientific observer program (2014-2019).

This study summarises six years of spatio-temporal patterns of the discarded demersal community fauna recorded by onboard scientific observer program for both artisanal and industrial crustacean fisheries between 2014 and 2019, from mesophotic to aphotic depths (96 to 650 m) along the southern Humboldt Current System (28-38°S). In this period, one cold and two warm climatic events were observed during the austral summer 2014, 2015-2016 (ENSO Godzilla), and 2016-2017 (coastal ENSO), respectively. Satellite information showed that Chlorophyll-a concentration varied seasonally and latitudinally, associated with upwelling centres, while equatorial wind stress decreased southward of 36°S. Discards were composed of 108 species, dominated by finfish and molluscs. The Chilean hake Merluccius gayi was dominant and ubiquitous (occurrence, 95% of 9104 hauls), being the most vulnerable species of the bycatch. Three assemblages were identified: assemblage 1 (~200 m deep), dominated by flounders Hippoglossina macrops and lemon crabs Platymera gaudichaudii, assemblage 2 (~260 m deep), dominated by squat lobsters Pleuroncodes monodon and Cervimunida johni and assemblage 3 (~320 m depth), dominated by grenadiers Coelorinchus aconcagua and cardinalfish Epigonus crassicaudus. These assemblages were segregated by depth, and varied by year, and geographic zone. The latter represented changes in the width of the continental shelf, increasing southward of 36°S. Alpha-diversity indexes (richness, Shannon, Simpson, and Pielou) also varied with depth and latitude, with higher diversity in deeper continental waters (>300 m), between 2018-2019. Finally, at a spatial scale of tens of kilometres, and a monthly basis, interannual variations of biodiversity occurred in the demersal community. Surface sea temperature, chlorophyll-a, or wind stress did not correlate with discarded demersal fauna diversity of the crustacean fishery operating along central Chile.

Comprehensive quality initiative leads to immediate postoperative extubation following liver transplant.

BACKGROUND: Immediate postoperative extubation (IPE) can reduce perioperative complications and length of stay (LOS), however it is performed variably after liver transplant across institutions and has historically excluded high-risk recipients from consideration. In late 2012, we planned and implemented a single academic institution structured quality improvement (QI) initiative to standardize perioperative care of liver transplant recipients without exceptions. We hypothesized that such an approach would lead to a sustained increase in IPE after primary (PAC) and delayed abdominal closure (DAC). METHODS: We retrospectively studied 591 patients from 2013 to 2018 who underwent liver transplant after initiative implementation. We evaluated trends in incidence of IPE versus delayed extubation (DE), and reintubation, LOS, and mortality. RESULTS: Overall, 476/591 (80.5%) recipients underwent PAC (278 IPE, 198 DE) and 115/591 (19.5%) experienced DAC (39 IPE, 76 DE). When comparing data from 2013 to data from 2018, the incidence of IPE increased from 9/67 (13.4%) to 78/90 (86.7%) after PAC and from 1/12 (8.3%) to 16/23 (69.6%) after DAC. For the same years, the incidence of IPE after PAC for recipients with MELD scores ≥30 increased from 0/19 (0%) to 12/17 (70.6%), for recipients who underwent simultaneous liver-kidney transplant increased from 1/8 (12.5%) to 4/5 (80.0%), and for recipients who received massive transfusion (>10 units of packed red blood cells) increased from 0/17 (0%) to 10/13 (76.9%). Reintubation for respiratory considerations <48 h after IPE occurred in 3/278 (1.1%) after PAC and 1/39 (2.6%) after DAC. IPE was associated with decreased intensive care unit (HR of discharge: 1.92; 95% CI: 1.58, 2.33; P < 0.001) and hospital LOS (HR of discharge: 1.45; 95% CI: 1.20, 1.76; P < 0.001) but demonstrated no association with mortality. CONCLUSION: A structured QI initiative led to sustained high rates of IPE and reduced LOS in all liver transplant recipients, including those classified as high risk.

Reactive persistence, spatial management, and conservation of metapopulations: An application to seagrass restoration.

Assessing the conditions for persistence of spatially structured populations, especially those that are exploited by humans or threatened by global change, is of critical importance to inform management and conservation efforts. Observations for entire metapopulations are usually incomplete and rarely, if ever, sufficiently long to deduce population persistence from spatial patterns of abundance. Instead, insights based on metapopulation theory are often used for interpreting the demographic trajectories of real populations and for informing management decisions. The classical theoretical tool used to assess conditions for metapopulation persistence is the "invasibility criterion," which characterizes the asymptotic, or long-term, stability of a small colonizing population. Essentially, when the linear operator governing the metapopulation dynamics of an invasion event has a positive eigenvalue, recovery and resistance to extinction (resilience) are implied. The converse, however, is not necessarily the case-an invasion may grow over multiple generations, even when the eigenvalues indicate that extinction will eventually occur, a situation referred to here as "reactive persistence." For the management, restoration, and conservation of real metapopulations subject to continual disturbance, this transient behavior is often more relevant than the asymptotic behavior over long time scales. We develop the theoretical tools for assessing reactive persistence, demonstrating how the conditions for asymptotic and reactive persistence differ in both the patch-occupancy models suited to many terrestrial populations and those where local patch extinctions can be disregarded in the dynamics, often suited to marine species. After presenting the mathematical basis for generalizing the invasibility criterion to include reactive persistence, we illustrate how these concepts and tools can be applied in practice, using as a case study the population ecology and restoration of the seagrass Zostera muelleri (Irmisch ex Ascherson, 1867) in the Port of Gladstone in the Great Barrier Reef World Heritage Area Australia. It is shown how the analysis of the transient dynamics of the Z. muelleri metapopulation can be used to guide restoration efforts. Moreover, it is demonstrated that these reactive persistence concepts provide a more appropriate basis for site prioritization for restoration interventions than traditional stability analysis.

A Decade of Death and Other Dynamics: Deepening Perspectives on the Diversity and Distribution of Sea Stars and Wasting.

AbstractMass mortality events provide valuable insight into biological extremes and also ecological interactions more generally. The sea star wasting epidemic that began in 2013 catalyzed study of the microbiome, genetics, population dynamics, and community ecology of several high-profile species inhabiting the northeastern Pacific but exposed a dearth of information on the diversity, distributions, and impacts of sea star wasting for many lesser-known sea stars and a need for integration across scales. Here, we combine datasets from single-site to coast-wide studies, across time lines from weeks to decades, for 65 species. We evaluated the impacts of abiotic characteristics hypothetically associated with sea star wasting (sea surface temperature, pelagic primary productivity, upwelling wind forcing, wave exposure, freshwater runoff) and species characteristics (depth distribution, developmental mode, diet, habitat, reproductive period). We find that the 2010s sea star wasting outbreak clearly affected a little over a dozen species, primarily intertidal and shallow subtidal taxa, causing instantaneous wasting prevalence rates of 5%-80%. Despite the collapse of some populations within weeks, environmental and species variation protracted the outbreak, which lasted 2-3 years from onset until declining to chronic background rates of ∼2% sea star wasting prevalence. Recruitment began immediately in many species, and in general, sea star assemblages trended toward recovery; however, recovery was heterogeneous, and a marine heatwave in 2019 raised concerns of a second decline. The abiotic stressors most associated with the 2010s sea star wasting outbreak were elevated sea surface temperature and low wave exposure, as well as freshwater discharge in the north. However, detailed data speaking directly to the biological, ecological, and environmental cause(s) and consequences of the sea star wasting outbreak remain limited in scope, unavoidably retrospective, and perhaps always indeterminate. Redressing this shortfall for the future will require a broad spectrum of monitoring studies not less than the taxonomically broad cross-scale framework we have modeled in this synthesis.

Hidden interactions in the intertidal rocky shore: variation in pedal mucus microbiota among marine grazers that feed on epilithic biofilm communities.

In marine ecosystems, most invertebrates possess diverse microbiomes on their external surfaces, such as those found in the pedal mucus of grazing gastropods and chitons that aids displacement on different surfaces. The microbes are then transported around and placed in contact with free-living microbial communities of micro and other macro-organisms, potentially exchanging species and homogenizing microbial composition and structure among grazer hosts. Here, we characterize the microbiota of the pedal mucus of five distantly related mollusk grazers, quantify differences in microbial community structure, mucus protein and carbohydrate content, and, through a simple laboratory experiment, assess their effects on integrated measures of biofilm abundance. Over 665 Amplicon Sequence Variants (ASVs) were found across grazers, with significant differences in abundance and composition among grazer species and epilithic biofilms. The pulmonate limpet Siphonaria lessonii and the periwinkle Echinolittorina peruviana shared similar microbiota. The microbiota of the chiton Chiton granosus, keyhole limpet Fissurella crassa, and scurrinid limpet Scurria araucana differed markedly from one another, and form those of the pulmonate limpet and periwinkle. Flavobacteriaceae (Bacteroidia) and Colwelliaceae (Gammaproteobacteria) were the most common among microbial taxa. Microbial strict specialists were found in only one grazer species. The pedal mucus pH was similar among grazers, but carbohydrate and protein concentrations differed significantly. Yet, differences in mucus composition were not reflected in microbial community structure. Only the pedal mucus of F. crassa and S. lessonii negatively affected the abundance of photosynthetic microorganisms in the biofilm, demonstrating the specificity of the pedal mucus effects on biofilm communities. Thus, the pedal mucus microbiota are distinct among grazer hosts and can affect and interact non-trophically with the epilithic biofilms on which grazers feed, potentially leading to microbial community coalescence mediated by grazer movement. Further studies are needed to unravel the myriad of non-trophic interactions and their reciprocal impacts between macro- and microbial communities.

Predator control of marine communities increases with temperature across 115 degrees of latitude.

Early naturalists suggested that predation intensity increases toward the tropics, affecting fundamental ecological and evolutionary processes by latitude, but empirical support is still limited. Several studies have measured consumption rates across latitude at large scales, with variable results. Moreover, how predation affects prey community composition at such geographic scales remains unknown. Using standardized experiments that spanned 115° of latitude, at 36 nearshore sites along both coasts of the Americas, we found that marine predators have both higher consumption rates and consistently stronger impacts on biomass and species composition of marine invertebrate communities in warmer tropical waters, likely owing to fish predators. Our results provide robust support for a temperature-dependent gradient in interaction strength and have potential implications for how marine ecosystems will respond to ocean warming.

Climate change in the coastal ocean: shifts in pelagic productivity and regionally diverging dynamics of coastal ecosystems.

Climate change has led to intensification and poleward migration of the Southeastern Pacific Anticyclone, forcing diverging regions of increasing, equatorward and decreasing, poleward coastal phytoplankton productivity along the Humboldt Upwelling Ecosystem, and a transition zone around 31° S. Using a 20-year dataset of barnacle larval recruitment and adult abundances, we show that striking increases in larval arrival have occurred since 1999 in the region of higher productivity, while slower but significantly negative trends dominate poleward of 30° S, where years of recruitment failure are now common. Rapid increases in benthic adults result from fast recruitment-stock feedbacks following increased recruitment. Slower population declines in the decreased productivity region may result from aging but still reproducing adults that provide temporary insurance against population collapses. Thus, in this region of the ocean where surface waters have been cooling down, climate change is transforming coastal pelagic and benthic ecosystems through altering primary productivity, which seems to propagate up the food web at rates modulated by stock-recruitment feedbacks and storage effects. Slower effects of downward productivity warn us that poleward stocks may be closer to collapse than current abundances may suggest.

A complication of ECMO cannula placement resulting in hemodynamic and oxygenation alterations: A case report.

Veno-veno extracorporeal membrane oxygenation (VV ECMO) is used as a bridge to recovery in acute respiratory distress syndrome (ARDS) patients who have reversible lung failure. We present a complication of ECMO cannula placement/position resulting in hemodynamic and oxygenation alterations. These demonstrate principles related to the interaction of the VV ECMO circuit and patient cardio-pulmonary physiology. Consideration and comprehension of pulmonary shunt fraction, ECMO cannula recirculation ratio and ECMO blood flow to cardiac output (CO) ratio are central to continuous assessment and diagnosis of cardio-pulmonary changes encountered during management of VV ECMO.

Testing the Test: A Comparative Study of Marine Microbial Corrosion under Laboratory and Field Conditions.

Microbially influenced corrosion (MIC) is an aggressive type of corrosion that occurs in aquatic environments and is sparked by the development of a complex biological matrix over a metal surface. In marine environments, MIC is exacerbated by the frequent variability in environmental conditions and the typically high diversity of microbial communities; hence, local and in situ studies are crucial to improve our understanding of biofilm composition, biological interactions among its members, MIC characteristics, and corrosivity. Typically, material performance and anticorrosion strategies are evaluated under controlled laboratory conditions, where natural fluctuations and gradients (e.g., light, temperature, and microbial composition) are not effectively replicated. To determine whether MIC development and material deterioration observed in the laboratory are comparable to those that occur under service conditions (i.e., field conditions), we used two testing setups, in the lab and in the field. Stainless steel (SS) AISI 316L coupons were exposed to southeastern Pacific seawater for 70 days using (i) acrylic tanks in a running seawater laboratory and (ii) an offshore mooring system with experimental frames immersed at two depths (5 and 15 m). Results of electrochemical evaluation, together with those of microbial community analyses and micrographs of formed biofilms, demonstrated that the laboratory setup provides critical information on the early biofilm development process (days), but the information gathered does not predict deterioration or biofouling of SS surfaces exposed to natural conditions in the field. Our results highlight the need to conduct further research efforts to understand how laboratory experiments may better reproduce field conditions where applications are to be deployed, as well as to improve our understanding of the role of eukaryotes and the flux of nutrients and oxygen in marine MIC events.

Alteration of coastal productivity and artisanal fisheries interact to affect a marine food web.

Top-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a top-down force can shorten and destabilize food webs, while effects driven by climate change can alter the bottom-up forces of primary productivity. We assessed the response of a highly-resolved intertidal food web to these two global change drivers, using network analysis and bioenergetic modelling. We quantified the relative importance of artisanal fisheries as another predator species, and evaluated the independent and combined effects of fisheries and changes in plankton productivity on food web dynamics. The food web was robust to the loss of all harvested species but sensitive to the decline in plankton productivity. Interestingly, fisheries dampened the negative impacts of decreasing plankton productivity on non-harvested species by reducing the predation pressure of harvested consumers on non-harvested resources, and reducing the interspecific competition between harvested and non-harvested basal species. In contrast, the decline in plankton productivity increased the sensitivity of harvested species to fishing by reducing the total productivity of the food web. Our results show that strategies for new scenarios caused by climate change are needed to protect marine ecosystems and the wellbeing of local communities dependent on their resources.

Geographical variation of multiplex ecological networks in marine intertidal communities.

Understanding the drivers of geographical variation in species distributions, and the resulting community structure, constitutes one of the grandest challenges in ecology. Geographical patterns of species richness and composition have been relatively well studied. Less is known about how the entire set of trophic and non-trophic ecological interactions, and the complex networks that they create by gluing species together in complex communities, change across geographical extents. Here, we compiled data of species composition and three types of ecological interactions occurring between species in rocky intertidal communities across a large spatial extent (~970 km of shoreline) of central Chile, and analyzed the geographical variability in these multiplex networks (i.e., comprising several interaction types) of ecological interactions. We calculated nine network summary statistics common across interaction types, and additional network attributes specific to each of the different types of interactions. We then investigated potential environmental drivers of this multivariate network organization. These included variation in sea surface temperature and coastal upwelling, the main drivers of productivity in nearshore waters. Our results suggest that structural properties of multiplex ecological networks are affected by local species richness and modulated by factors influencing productivity and environmental predictability. Our results show that non-trophic negative interactions are more sensitive to spatially structured temporal environmental variation than feeding relationships, with non-trophic positive interactions being the least labile to it. We also show that environmental effects are partly mediated through changes in species richness and partly through direct influences on species interactions, probably associated to changes in environmental predictability and to bottom-up nutrient availability. Our findings highlight the need for a comprehensive picture of ecological interactions and their geographical variability if we are to predict potential effects of environmental changes on ecological communities.

Novel co-occurrence of functionally redundant consumers induced by range expansion alters community structure.

Ongoing climate change is shifting the geographic distributions of some species, potentially imposing rapid changes in local community structure and ecosystem functioning. Besides changes in population-level interspecific interactions, such range shifts may also cause changes in functional structure within the host assemblages, which can result in losses or gains in ecosystem functions. Because consumer-resource dynamics are central to community regulation, functional reorganization driven by introduction of new consumer species can have large consequences on ecosystem functions. Here we experimentally examine the extent to which the recent poleward range expansion of the intertidal grazer limpet Scurria viridula along the coast of Chile has altered the role of the resident congeneric limpet S. zebrina, and whether the net collective impacts, and functional structure, of the entire herbivore guild have been modified by the introduction of this new member. We examined the functional role of Scurria species in controlling ephemeral algal cover, bare rock availability, and species richness and diversity, and compared the effects in the region of range overlap against their respective "native" abutted ranges. Experiments showed depression of per capita effects of the range-expanded species within the region of overlap, suggesting environmental conditions negatively affect individual performance. In contrast, effects of S. zebrina were commonly invariant at its range edge. When comparing single species versus polycultures, effects on bare rock cover were altered by the presence of the other Scurria species, suggesting competition between Scurria species. Importantly, although the magnitude of S. viridula effects at the range overlap was reduced, its addition to the herbivore guild seems to complement and intensify the role of the guild in reducing green algal cover, species richness and increasing bare space provision. Our study thus highlights that range expansion of an herbivore can modify the functional guild structure in the recipient community. It also highlights the complexity of predicting how functional structure may change in the face of natural or human-induced range expansions. There is a need for more field-based examination of regional functional compensation, complementarity, or inhibition before we can construct a conceptual framework to anticipate the consequences of species range expansions.

Incorporating the Connectivity Timescale in Metapopulation Partitioning.

The often complex spatial patterns of propagule dispersal across a metapopulation present a challenge for species management, motivating efforts to represent the connectivity in simpler but meaningful ways. The reduction of complexity may be achieved by partitioning the metapopulation into groups of highly connected patches called "subpopulations." To have relevance for management, these subunits must be defined from ecological or evolutionary principles. The probabilities of dispersal-mediated propagule interchange between sites, commonly organized into a connectivity matrix, entail a timescale that is usually ignored in subpopulation analyses, limiting their utility and possibly leading to misinterpretation and wrong management decisions. Recognition of the essentially dynamical role played by metapopulation connectivity naturally leads to the incorporation of the generational timescale into the partitioning analysis. An algorithm is proposed to determine the subpopulations-both their cardinality and their composition-as a function of the generational timescale and of a limiting probability of connection, illustrated with a novel empirical estimate of mesopelagic connectivity. The proposed framework allows the unambiguous determination of the timescales corresponding to dispersal barriers and the identification of effective ecological units across the spectrum of management-relevant time horizons.