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Rocky shores typically exhibit a variety of sedentary and free-moving forms of epibionts associated with the shells of mussel basibionts. This paper provides a first report on epibiotic bryozoans found on shells of the invasive Mediterranean mussel, Mytilus galloprovincialis Lamarck. More than 2500 mussels were collected between December 2019 and October 2020 from rocky shores during low spring tides across the south–southeast coast of South Africa. Ten percent of these mussels hosted epibiotic bryozoans. We examined a subset of these epibiotised mussels to assess the diversity of bryozoans. Three encrusting cheilostome species were identified: Chaperia atypica n. sp., Celleporella hyalina (Linnaeus), and Hippomonavella sp. This new species is the first Chaperia with avicularia and the first South African species with ooecia. This study highlights the biological diversity of epibiotic bryozoans on mussel shells and, given their differences in microtopography, the possibility that invasive species can provide a new substratum for rare, overlooked or undescribed species of epibionts.

We tested the response of algal epifauna to the direct effects of predation and the indirect consequences of habitat change due to grazing and nutrient supply through upwelling using an abundant intertidal rhodophyte, Gelidium pristoides. We ran a mid‐shore field experiment at four sites (two upwelling sites interspersed with two non‐upwelling sites) along 450 km of the south coast of South Africa. The experiment was started in June 2014 and ran until June 2015. Four treatments (predator exclusion, grazer exclusion, control, and procedural control) set out in a block design (n = 5) were monitored monthly for algal cover for the first 6 months and every 2 months for the last 6 months. Epifaunal abundance, species composition, algal cover, and algal architectural complexity (measured using fractal geometry) were assessed after 12 months. Predation had no significant effect on epifaunal abundances, while upwelling interacted with treatment. Grazing reduced the architectural complexity of algae, with increased fractal dimensions in the absence of grazers, and also reduced algal cover at all sites, though the latter effect was only significant for upwelling sites. Epifaunal community composition was not significantly affected by the presence of herbivores or predators but differed among sites independently of upwelling; sites were more similar to nearby sites than those farther away. In contrast, total epifaunal abundance was significantly affected by grazing, when normalized to algal cover. Grazing reduced the cover of algae; thus, epifaunal abundances were not affected by the direct top‐down effects of predation but did respond to the indirect effects of grazing on habitat availability and quality. Our results indicate that epifaunal communities can be strongly influenced by the indirect consequences of biotic interactions., Epifauna respond to the indirect effects of top‐down regulation of their habitat, rather than to the bottom‐up effects of nutrient availability, or the direct top‐down effects of predation.

We compiled known occurrence records of seven species of crabs identified in the literature and one documented in this report as having undergone range extensions in southern Africa. Of these eight species, six (Austruca occidentalis, Neosarmatium africanum, Ocypode ceratophthalmus, Portunus segnis, Tubuca urvillei, and Varuna litterata) have extended their ranges either across a major biogeographic boundary that separates the subtropical and warm temperate ecoregions of this coast, or into estuaries that historically lack mangrove forests. For the seventh and eighth species, Charybdis smithii and Scylla serrata, we were unable to find any distributional data that supported poleward range extension. In addition, we contribute the first record of the blue swimming crab, P. segnis, from the temperate south coast of South Africa. This early detection is likely to be part of an ongoing regional trend of tropical-adapted brachyuran crab species extending their ranges into temperate ecoregions.

Heat-induced mass mortalities involving ecosystem engineers may have long-lasting detrimental effects at the community level, eliminating the ecosystem services they provide. Intertidal mussels are ecologically and economically valuable with some populations facing unprecedented heat-induced mass mortalities. Critically, mussels are also frequently infested by endolithic parasites that modify shell albedo, hence reducing overheating and mortality rates under heat stress. Using a biophysical model, we explored the topographical and meteorological conditions under which endolithically driven thermal buffering becomes critical to survival. Based on meteorological data from a global climate analysis, we modelled body temperatures of infested and non-infested mussels over the last decade (2010-2020) at nine sites spread across c. 20 degrees of latitude. We show that thermal buffering is enhanced where and when heat stress is greatest, that is, on sun-exposed surfaces under high solar radiation and high air temperature. These results suggest that new co-evolutionary pathways are likely to open for these symbiotic organisms as climate continues to change, potentially tipping the balance of the relationship from a parasitic to a more mutualistic one. However, endolithically driven reductions in body temperatures can also occur at or below optimal temperatures, thereby reducing the host's metabolic rates and making the interplay of positive and negative effects complex. In parallel, we hindcasted body temperatures using empirical data from nearby weather stations and found that predictions were very similar with those obtained from two global climate reanalyses (i.e. NCEP-DOE Reanalysis 2 and ECMWF Reanalysis v5). This result holds great promise for modelling the distribution of terrestrial ectotherms at ecologically relevant spatiotemporal scales, as it suggests we can reasonably bypass the practical issues associated with weather stations. For intertidal ectotherms, however, the challenge will be incorporating body temperatures over the full tidal cycle. info:eu-repo/semantics/publishedVersion

We hypothesized congruence in the spatial structure of abundance data sampled across multiple scales for an ecological guild of consumers that exploit similar nutritional and habitat resources. We tested this hypothesis on the spatial organization of abundance of an herbivorous guild of sea urchins. We also examined whether the amount of local along‐shore rocky habitat can explain the observed spatial patterns of abundance. Standardized estimates of abundance of four intertidal sea urchins—Diadema cf. savignyi, Echinometra mathaei, Parechinus angulosus, and Stomopneustes variolaris—were determined by six observers at 105 sites across 2,850 km of coast of South Africa. For each species and observer, wavelet analysis was used on abundance estimates, after controlling for potential biases, to examine their spatial structure. The relationship between local sea urchin abundance and the amount of upstream and downstream rocky habitat, as defined by the prevailing ocean current, was also investigated. All species exhibited robust structure at scales of 75–220 km, despite variability among observers. Less robust structure in the abundances of three species was detected at larger scales of 430–898 km. Abundance estimates of sympatric populations of two species (D. cf. savignyi and E. mathaei) were positively correlated with the amount of rocky habitat upstream of the site, suggesting that upstream populations act as larval sources across a wide range of scales. No relationship between abundance and habitat size was found for P. angulosus or S. variolaris. Within the range of scales examined, we found robust congruence in spatial structure in abundance at the lower, but not the larger, range of scales for all four species. The relationship between abundance and upstream habitat availability in two species suggests that larval supply from upstream populations was probably the mechanism linking habitat size and abundance., We hypothesized and demonstrated congruence in the spatial structure of abundance data sampled across multiple scales for an ecological guild of consumers that exploit similar nutritional and habitat resources. We tested this hypothesis on the spatial organization of abundance of an herbivorous guild of intertidal sea urchins across 2,850 km of coast of South Africa. We also examined whether the amount of local along‐shore rocky habitat can explain the observed spatial patterns of abundance, which was the case for two of four focal species.

Studies of climate change effects on individuals and populations are mostly couched in terms of lethal temperature limits, but 2 other elements make predictions difficult: the effects of sublethal stress and intraspecific variability. Sublethal stress, such as exposure to highly variable temperatures, can cause carryover effects that influence how an animal responds to subsequent events and its long-term fitness. Additionally, intra-specific genetic variability can allow more complex species responses to climate change. We used 2 genetically distinct lineages of the intertidal mussel Perna perna to investigate the effects of sublethal temperature variability and genetic identity on thermal sensitivity estimates derived from standard metabolic rate measurements. Mussels were exposed to one of 3 acclimation treatments: measurements done immediately after collection (i.e. field fresh), or exposure to 2 wk of either constant temperature or fluctuating temperatures. The mussels were then exposed to rising temperatures within the range normally experienced in the field while oxygen consumption was recorded. We found no effect of lineage or treatment on the aerobic standard metabolic rate of mussels, but Q10, a proxy for thermal sensitivity, was influenced by treatment. While Q10 values under constant temperature did not differ significantly from those for field-fresh mussels, both were significantly lower than for fluctuating temperatures. Thus, temperature variability increased thermal sensitivity, but our results indicate that this was independent of genetic identity. Chronic increased temperature variability and repeated exposure to high (but sublethal) temperatures under climate change are likely to increase mussel temperature sensitivity and decrease performance. Such alterations to fitness are expected to occur before animals are exposed to lethal temperatures.

Aim Biogeographic boundaries can act as either weak or strong barriers to the spread of species undergoing distributional change. Once a novel species spreads across a boundary, it can have a substantial impact on the ecosystem, for instance by competing with local species, and, over the long‐term, re‐engineer the ecosystem. Marine biogeographic regions are clearly defined on the coast of southern Africa and we tested the influence of their boundaries on the spread and spatial structure of an alien ecosystem engineer. Location Southern Africa. Taxon An invasive mussel, Mytilus galloprovincialis. Methods Records of M. galloprovincialis were compiled into a database to determine its decadal patterns of spread across multiple bioregions. Distribution and abundance (estimated using density and semi‐quantitative abundance scale [ACFOR]) of this mussel were surveyed to determine patterns in spatial structure across bioregions. In addition, we compared the size structure of populations at the eastern margins of its range with those of larger populations nearer the range centre. Results Initial breaching of biogeographic boundaries was associated with rapid spread, but other boundaries encountered decades later acted as barriers to further spread. Across >2,800 km of coast, spatial autocorrelation was observed in densities (low and mid shore levels) and in ACFOR abundances. Repeating spatial patterns in densities and ACFOR abundance were detected at scales of 120–160 km and of 400–990 km. Considerable effort was required to detect populations at the absolute eastern limits of its distribution. Main conclusion Detection of spatial structures at multiple scales suggests that ecologically determined processes regulate abundance at both intra‐bioregional and inter‐bioregional scales, which may help tease apart the historic and contemporary consequences of interspecific interactions on the structure of rocky shore communities. This study demonstrates the influence of biogeography in driving temporal patterns of spread and spatial structure on the distribution and abundance of an invasive species.

Self-organized, regular spatial patterns emerging from local interactions among individuals enhance the ability of ecosystems to respond to environmental disturbances. Mussels self-organize to form large, regularly patterned biogenic structures that modify the biotic and abiotic environment and provide numerous ecosystem functions and services. We used two mussel species that form monospecific and mixed beds to investigate how species-specific behavior affects self-organization and resistance to wave stress. Perna perna has strong attachment but low motility, while Mytilus galloprovincialis shows the reverse. At low density, the less motile P. perna has limited spatial self-organization compared with M. galloprovincialis, while when coexisting, the two species formed random spatial patterns. At high density, the two species self-organized in similar ways, while when coexisting, patterns were less strong. Spatial pattern formations significantly shaped resistance to hydrodynamic stress. At low density, P. perna beds with strong attachment and M. galloprovincialis beds with strong spatial organization showed higher retention rates than mixed beds. At high density, the presence of strongly attached P. perna significantly increased retention in mixed and P. perna beds compared with M. galloprovincialis beds. Our study emphasizes the importance of the interplay of species-specific behaviors to spatial self-organization and stress tolerance in natural communities. National Research Foundation of South AfricaNational Research Foundation - South Africa [64801]; Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal); French Ministere de l'Enseignement Superieur et de la Recherche; Hauts de France RegionRegion Hauts-de-France; European Funds for Regional Economical Development

The physical properties of habitats are crucial determinants of community structure with significant effects on food web dynamics. We examined the effects of rock pool physical properties (e.g. pool size, water depth) and short-term temporal (seasonal) change (e.g. temperature, nutrients) on food web structure at small spatial scales (c. 500 m) on the warm temperate coast of South Africa. Using stable carbon and nitrogen isotope signatures, we characterised food web structure with Layman metrics and quantified food web size, defined as the total area in isotopic space occupied by consumer species. The effects of rock pool physical properties and seasonal changes on species counts and food web structure were evaluated using a Bayesian generalised linear mixed model approach. Substratum type, water depth, pool size, phosphate concentrations, salinity and temperature all influenced overall food web dynamics. A winter reduction of sand cover led to a more heterogeneous substratum and a significant increase in species counts, while consumer niche similarity decreased with increasing pool size in summer. The range of δ15N values, or trophic height, was negatively and positively affected by salinity and phosphate levels, respectively. Overall, the effects of pool physical properties on food web structure were moderated by seasonality.

The invasion history and current distribution of the alien marine mussel, the bisexual mussel Semimytilus algosus, on rocky shores of South Africa is described in this study. The eastern edge of it...

Herbivory is a key process that controls the abundance and accumulation of algal turf on tropical coral reefs. The capacity of reefs to prevent algal accumulation hinges on the balance between algal production and consumption (i.e., grazing). In this study, we quantify algal turf biomass accumulation and grazing using experimental substrata and herbivore exclusion cages across sites in Kenya that represent different levels of fisheries management: heavily fished reefs, community marine-protected areas less than 10 yr old, and older government-managed marine-protected areas. These reefs had different assemblages of grazing herbivores with fished reefs being dominated by sea urchins, while government closures had a high abundance of grazing fishes, in particular parrotfishes. The community fisheries closures had an intermediate mix of sea urchins and grazing fishes, with the latter dominated by surgeonfishes. These management regimes mediated algal biomass on experimental substrata such that urchins consumed as much as 90% on fished reefs and fishes as much as 96% at the government marine-protected areas by the end of the 390-d trial. The younger community fisheries closures lacked the herbivory to significantly reduce algal biomass, and consumption was less than 50% of production and never greater than 2 g algae m−2 d−1. These findings point to the importance of recovery dynamics of herbivorous fishes from heavy fishing pressure. They also suggest that while sea urchins might be effective grazers to prevent macroalgal dominance, they are not a functional replacement for fishes due to their ability to reduce reef accretion through bioerosion and prevent settlement of crustose coralline algae in this system.

Human activities alter patterns of biodiversity, particularly through species extinctions and range shifts. Two of these activities are human mediated transfer of species and contemporary climate change, and both allow previously isolated genotypes to come into contact and hybridize, potentially altering speciation rates. Hybrids have been shown to survive environmental conditions not tolerated by either parent, suggesting that, under some circumstances, hybrids may be able to expand their ranges and perform well under rapidly changing conditions. However, studies assessing how hybridization influences contemporary range shifts are scarce. We performed crosses on Pyura herdmani and Pyura stolonifera (Chordata, Tunicata), two closely related marine invertebrate species that are ecologically dominant and can hybridize. These sister species live in sympatry along the coasts of southern Africa, but one has a disjunct distribution that includes northern hemisphere sites. We experimentally assessed the performance of hybrid and parental crosses using different temperature regimes, including temperatures predicted under future climate change scenarios. We found that hybrids showed lower performance than parental crosses at the experimental temperatures, suggesting that hybrids are unlikely to expand their ranges to new environments. In turn, we found that the more widespread species performed better at a wide array of temperatures, indicating that this parental species may cope better with future conditions. This study illustrates how offspring fitness may provide key insights to predict range expansions and how contemporary climate change may mediate both the ability of hybrids to expand their ranges and the occurrence of speciation as a result of hybridization.

Mussels are ecological engineers in intertidal communities; they afect coastal species richness by increasing habitat spatial complexity, bufering against environmental extremes, and providing protection from predators. Parasitic activities of endolithic cyanobacteria on mussels weaken their shells, requiring the expenditure of energy on shell repair, with potential indirect efects on organisms that rely on mussels as habitat providers. Given the seasonality of reproduction and the need for strong attachment during winter storms, we examined the consequences of redirecting energy for shell repair to two other energetically expensive processes: reproduction and byssal attachment. We examined seasonality in the efects of cyanobacterial infestation on reproduction and attachment strength in two intertidal mussels, the indigenous Perna perna and the invasive Mytilus galloprovincialis from the south coast of South Africa, using both qualitative and quantitative analyses. Reproductive efects were examined by measuring the weight of mussel gonads and the density of eggs within each gonad for co-occurring infested and non-infested mussels, while attachment strength was measured for mussels exhibiting diferent levels of infestation. Endolithic infestation was found to afect reproduction by reducing the mass of gonads, but not the density of eggs within them. Attachment strength was closely correlated with the degree of endolithic infestation, with very infested mussels requiring much less force to detach them from the substratum than mussels with low or no infestation. Thus, endolithic infestation afected mussel ftness directly, by increasing the probably of mortality through wave dislodgement and by reducing reproductive output. info:eu-repo/semantics/publishedVersion

Recruitment of mussels is a complex process with the successful arrival of individuals hinging on the availability of suitable habitats. We examined the effects of adult mussels as settlement habitat and the degree to which the suitability of habitat they offer is species-specific by comparing the recruitment success of intertidal mussels. We hypothesised that mussel recruitment and early growth are dictated by the quality of habitat offered by conspecifics adults. We used a unique experimental arena on the south coast of South Africa, where Mytilus galloprovincialis and two lineages of Perna perna co-exist. Treatments were based on the translocation of individuals of M. galloprovincialis, western- and eastern lineage of P. perna to a single site, where artificial beds were created and sampled monthly over one year. Recruit's number, their sizes and growth were greater within beds of the western lineage of Perna than eastern lineage or Mytilus beds. The results clearly demonstrate that the quality of settlement habitat offered by adult beds differs among adult lineages/species and affects rates of settlement and the early growth of recruits. This effect extends to the intraspecific level; we found greater differences in density and growth of recruits between lineages of Perna than between either lineage and M. galloprovincialis. info:eu-repo/semantics/publishedVersion

Research on the genetics of invasive species often focuses on patterns of genetic diversity and population structure within the introduced range. However, a growing body of literature is demonstrating the need to study the native range, and how native genotypes affect both ecological and evolutionary mechanisms within the introduced range. Here we used genotyping-by-sequencing to study both native and introduced ranges [based on 1,653 single nucleotide polymorphisms (SNPs)] of the amphiatlantic marine invertebrate Ciona intestinalis. A previous study using microsatellites analysed samples collected along the Swedish west coast and showed the presence of genetically distinct lineages in deep and shallow waters. Using our SNP data from newly collected samples (285 individuals), we first confirmed the presence of this depth-defined genomic divergence along the Swedish coast. We then used Approximate Bayesian Computation to infer the historical relationship among sites from the North Sea, the English Channel and the northwest Atlantic and found evidence of ancestral divergence between individuals from deep waters off Sweden and individuals from the English Channel. This divergence was followed by a secondary contact that led to a genetic admixture between the ancestral populations (i.e. deep Sweden and English Channel), which originated the genotypes found in shallow Sweden. We then revealed that the colonisation of C. intestinalis in the northwest Atlantic was as a result of an admixture between shallow Sweden and the English Channel genotypes across the introduced range. Our results showed the presence of both past and recent genetic admixture events that together may have promoted the successful colonisations of C. intestinalis. Our study suggests that secondary contacts potentially reshape the evolutionary trajectories of invasive species through the promotion of intraspecific hybridisation and by altering both colonisation patterns and their ecological effects in the introduced range.,Hudson_etal.2019_Ciona_1653loci.vcf VCF file containing 1653 putatively neutral SNPs as outlined in the associated manuscript. Hudson_etal.2019_SampleID.txt Text file containing sample ID from the VCF files and the appropriate sampling location. Abbreviations as in Table 1 of associated manuscript.

Our understanding of how anthropogenic stressors such as climate change and plastic pollution interact with biodiver-sity is being widened to include diversity below the species level, i.e., intraspecific variation. The emerging apprecia-tion of the key ecological importance of intraspecific diversity and its potential loss in the Anthropocene, further highlights the need to assess the relative importance of intraspecific versus interspecific diversity. One such issue is whether a species responds as a homogenous whole to plastic pollution. Using manipulative field transplant experi-ments and laboratory-controlled hydrodynamic simulations, we assessed the relative effects of intraspecific and inter -specific diversity on microplastic trapping in coastal biogenic habitats dominated by two key bioengineers, the brown intertidal macroalgae Fucus vesiculosus and F. guiryi. At the individual level, northern morphotypes of F. guiryi trapped more microplastics than southern individuals, and F. vesiculosus trapped more microplastics than F. guiryi. Canopy den-sity varied among species, however, leading to reversed patterns of microplastic accumulation, with F. guiryi canopies accumulating more microplastics than those of F. vesiculosus, while no differences were observed between the canopies of F. guiryi morphotypes. We emphasize the importance of assessing the effects of intraspecific variation which, along with other crucial factors such as canopy density, flow velocity and polymer composition, modulates the extent of microplastic accumulation in coastal biogenic habitats. Our findings indicate that a realistic estimation of plastic accu-mulation in biogenic habitats requires an understanding of within-and between-species traits at both the individual and population levels. info:eu-repo/semantics/publishedVersion

Euendolithic, or true-boring, cyanobacteria actively erode carbonate-containing substrata in a wide range of environments and pose significant risks to calcareous marine fauna. Their boring activities cause structural damage and increase susceptibility to disease and are projected to only intensify with global climate change. Most research has, however, focused on tropical coral systems, and limited information exists on the global distribution, diversity, and substratum specificity of euendoliths. This metastudy aimed to collate existing 16S rRNA gene surveys along with novel data from the south coast of South Africa to investigate the global distribution and genetic diversity of endoliths to identify a "core endolithic cyanobacterial microbiome" and assess global diversification of euendolithic cyanobacteria. The cyanobacterial families Phormidesmiaceae, Nodosilineaceae, Nostocaceae, and Xenococcaceae were the most prevalent, found in92% of categories surveyed. All four known euendolith clusters were detected in both intertidal and subtidal habitats, in the North Atlantic, Mediterranean, and South Pacific oceans, across temperate latitudes, and within rock, travertine tiles, coral, shell, and coralline algae substrata. Analysis of the genetic variation within clusters revealed many organisms to be unique to substratum type and location, suggesting high diversity and niche specificity. Euendoliths are known to have important effects on their hosts. This is particularly important when hosts are globally significant ecological engineers or habitat-forming species. The findings of this study indicate high ubiquity and diversity of euendolithic cyanobacteria, suggesting high adaptability, which may lead to increased community and ecosystem-level effects with changing climatic conditions favoring the biochemical mechanisms of cyanobacterial bioerosion.

The KwaZulu-Natal sardine run, popularly known as the “greatest shoal on Earth,” is a mass migration of South African sardines from their temperate core range into the subtropical Indian Ocean. It has been suggested that this represents the spawning migration of a distinct subtropical stock. Using genomic and transcriptomic data from sardines collected around the South African coast, we identified two stocks, one cool temperate (Atlantic) and the other warm temperate (Indian Ocean). Unexpectedly, we found that sardines participating in the sardine run are primarily of Atlantic origin and thus prefer colder water. These sardines separate from the warm-temperate stock and move into temporarily favorable Indian Ocean habitat during brief cold-water upwelling periods. Once the upwelling ends, they find themselves trapped in physiologically challenging subtropical habitat and subject to intense predation pressure. This makes the sardine run a rare example of a mass migration that has no apparent fitness benefits.

Stable isotopes are widely used in ecosystem studies to decipher trophic relationships between species. Using stable isotopes as trophic markers requires knowledge of the stable isotope ratios of consumer and putative prey, and of trophic discrimination factors (TDFs), the difference between the stable isotope ratios of predator and prey. TDFs differ among species, tissue sampled and the consumer’s physiological state. We tested whether consumer ontogeny also influences its stable isotope ratios by measuring the δ13C and δ15N values, and their associated TDFs, of African penguin (Spheniscus demersus) blood components (whole blood, red blood cells, plasma) among four age classes (chicks, fledglings, juveniles and adults). Blood was sampled from captive penguins concurrently with their diet. Ontogenetic effects on TDFs were complex, depending on the blood component and isotope considered. Blood components differed in their sensitivity to consumer physiology, but TDFs for both carbon and nitrogen were generally lower for the younger age classes. Age class influenced the stable isotope compositions of whole blood and red blood cells with chicks and fledglings exhibiting significantly lower δ13C and δ15N values than juveniles and adults. Plasma showed no effect of ontogeny. The results indicate age class affects stable isotope ratios and TDFs through ontogenetic changes in physiology. Therefore, when uncertainty concerning TDFs exists in studies of wild animals, stable isotope analysis should preferably be combined with other dietary techniques.

A central theme in community ecology is understanding how similar species co‐exist and how their interactions may evolve in the context of climate change. Most studies of resource partitioning among central place foragers, particularly birds, focus on the offspring‐rearing period, when they are accessible, but breeding success may be determined earlier and little is known about how such species partition resources at the onset of breeding. We used a non‐invasive approach to evaluate resource partitioning in co‐existing females at a sub‐Antarctic island during their pre‐laying periods. Three hypotheses were tested using carbon, nitrogen and oxygen stable isotope ratios measured in shells and membranes of hatched eggs as ecological tracers: 1) resource partitioning by geographic location and trophic level will exist among the 12 bird species and will be enhanced within taxonomic groups; 2) given the absence of strong oxygen gradients in the Southern Ocean we will not detect spatial structuring based on oxygen isotopes, but differences will exist between resident and oceanic species as the former may use meteoric water; 3) capital and income breeder strategies can be differentiated using stable isotopes of egg remains. Two and three dimensional isotopic data showed resource partitioning among species. As predicted, segregation was evident within the four main taxonomic groups: penguins, albatrosses, burrowing petrels and giant petrels. Unexpectedly, oxygen isotopes revealed widespread use of meteoric water among a suite of sub‐Antarctic birds. Stable isotopes allowed us to identify females of most species as income breeders at the onset of breeding, with the exception of the females of the two crested penguin exhibiting a mix of income and capital resources use. Multidimensional isotopic analyses revealed that resource partitioning exists at multiple stages of the annual cycle in ways likely to be important under global change, exhibiting wide potential for ecosystem analysis.

Predicting the spread of invasive species in a warming world calls for a better understanding of the mechanisms behind the relative performance of both invasive and indigenous species as recipient communities can offer biotic resistance. A particularly important functional trait in this context is reproductive potential. The Mediterranean mussel Mytilus galloprovincialis is invasive world-wide and threatens the native brown mussel Perna perna on South African rocky shores. Where they co-exist, Mytilus dominates the high and Perna the low mussel zone, overlapping in the middle. Mytilus generally exhibits high individual reproductive output, but feeding time is reduced, physical conditions are stressful and adult densities are lower on the higher shore. We compared overall reproductive potential of populations of the two species using a 1-year data set for three sites, accounting for within-shore distribution and abundances. Despite the restriction of Mytilus to the more stressful upper-shore, its aggregate reproductive potential was comparable to that of Perna. We then used Dynamic Energy Budget modelling to test the effects of changing conditions by calculating aggregate reproductive potential under temperature conditions predicted for the end of the century by the International Panel on Climate Change. The results suggest increased aggregate reproductive potential for both species, but the effect was stronger for the native species at two of three sites, implying increased biotic resistance by Perna to the further spread of Mytilus. Combining ecological context and physiological performance elucidates how interactions between native and invasive species may alter. Such nuances are fundamental to anticipating winners or losers in a world where distribution shifts are increasingly common.

Effective conservation requires maintenance of the processes underlying species divergence, as well as understanding species’ responses to episodic disturbances and long-term change. We explored genetic population structure at a previously unrecognized spatial scale in seabirds, focusing on fine-scale isolation between colonies, and identified two distinct genetic clusters of Barau’s Petrels (Pterodroma baraui) on Réunion Island (Indian Ocean) corresponding to the sampled breeding colonies separated by 5 km. This unexpected result was supported by long-term banding and was clearly linked to the species’ extreme philopatric tendencies, emphasizing the importance of philopatry as an intrinsic barrier to gene flow. This implies that loss of a single colony could result in the loss of genetic variation, impairing the species’ ability to adapt to threats in the long term. We anticipate that these findings will have a pivotal influence on seabird research and population management, focusing attention below the species level of taxonomic organization.

Este artículo contiene 7 páginas, 3 figuras., Explaining why some species are widespread, while others are not, is fundamental to biogeography, ecology, and evolutionary biology. A unique way to study evolutionary and ecological mechanisms that either limit species’ spread or facilitate range expansions is to conduct research on species that have restricted distributions. Nonindigenous species, particularly those that are highly invasive but have not yet spread beyond the introduced site, represent ideal systems to study range size changes. Here, we used species distribution modeling and genomic data to study the restricted range of a highly invasive Australian marine species, the ascidian Pyura praeputialis. This species is an aggressive space occupier in its introduced range (Chile), where it has fundamentally altered the coastal community. We found high genomic diversity in Chile, indicating high adaptive potential. In addition, genomic data clearly showed that a single region from Australia was the only donor of genotypes to the introduced range. We identified over 3,500 km of suitable habitat adjacent to its current introduced range that has so far not been occupied, and importantly species distribution models were only accurate when genomic data were considered. Our results suggest that a slight change in currents, or a change in shipping routes, may lead to an expansion of the species’ introduced range that will encompass a vast portion of the South American coast. Our study shows how the use of population genomics and species distribution modeling in combination can unravel mechanisms shaping range sizes and forecast future range shifts of invasive species., M.R. received funds from ASSEMBLE (a European Union Seventh Framework Programme research infrastructure initiative comprising a network of marine research stations) to visit the Estación Costera de Investigaciones Marinas de Las Cruces and the Pontificia Universidad Católica de Chile. P.R.T. was supported by the University of Johannesburg (Faculty Research Committee/ University Research Committee grant) and L.B.B. by the Australian Research Council. J.C.C. acknowledges financial support from the Nucleo Milenio en Conservación Marina. J.C.C. sincerely acknowledges long-term financial support (Pontificia Universidad Católica de Chile–Escondida Project) fromMinera Escondida Ltda, the last 10-y support from the Academic Chair “Arauco-UC” and the important and constant assistance and advice from Dr. PatricioManríquez. C.D.M. received funding fromthe South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation (Grant 64801).

Temperature extremes are predicted to intensify with climate change. These extremes are rapidly emerging as a powerful driver of species distributional changes with the capacity to disrupt the functioning and provision of services of entire ecosystems, particularly when they challenge ecosystem engineers. The subsequent search for a robust framework to forecast the consequences of these changes mostly ignores within-species variation in thermal sensitivity. Such variation can be intrinsic, but can also reflect species interactions. Intertidal mussels are important ecosystem engineers that host symbiotic endoliths in their shells. These endoliths unexpectedly act as conditionally beneficial parasites that enhance the host's resistance to intense heat stress. To understand how this relationship may be altered under environmental change, we examined the conditions under which it becomes advantageous by reducing body temperature. We deployed biomimetic sensors (robomussels), built using shells of mussels (Mytilus galloprovincialis) that were or were not infested by endoliths, at nine European locations spanning a temperature gradient across 22 degrees of latitude (Orkney, Scotland to the Algarve, Portugal). Daily wind speed and solar radiation explained the maximum variation in the difference in temperature between infested and non-infested robomussels; the largest difference occurred under low wind speed and high solar radiation. From the robomussel data, we inferred body temperature differences between infested and non-infested mussels during known heatwaves that induced mass mortality of the mussel Mytilus edulis along the coast of the English Channel in summer 2018 to quantify the thermal advantage of endolith infestation during temperature extremes. Under these conditions, endoliths provided thermal buffering of between 1.7 degrees C and 4.8 degrees C. Our results strongly suggest that sustainability of intertidal mussel beds will increasingly depend on the thermal buffering provided by endoliths. More generally, this work shows that biomimetic models indicate that within-species thermal sensitivity to global warming can be modulated by species interactions, using an intertidal host-symbiont relationship as an example. Fundacao para a Ciencia e TecnologiaPortuguese Foundation for Science and TechnologyEuropean Commission [UIDB/04326/2020]; National Research Foundation of South AfricaNational Research Foundation - South Africa [64801]; Department of Science and TechnologyDepartment of Science & Technology (India); National FoundationNational Science Foundation (NSF); South African National Research FoundationNational Research Foundation - South Africa; French Ministere de l'Enseignement Superieur et de la Recherche; Hauts de France RegionRegion Hauts-de-France; European Funds for Regional Economical Development info:eu-repo/semantics/publishedVersion

Plastic pollution is ubiquitous with increasing recognition of its direct effects on species’ fitness. Little is known, however, about its more subtle effects, including the influence of plastic pollution on the morphological, functional and behavioral traits of organisms that are central to their ability to withstand disturbances. Among the least obvious but most pernicious forms of plastic-associated pollution are the chemicals that leach from microplastics. Here, we investigate how such leachates influence species’ traits by assessing functional trait compensation across four species of intertidal mussels, through investigations of byssal thread production, movement and aggregation behavior for mussels held in natural seawater or seawater contaminated by microplastic leachates. We found no evidence for compensation of functional traits, but for each species, microplastic leachates reinforced one trait while others remained unaffected. Two species (Perna perna and Mytilus galloprovincialis), were characterized by a resistance strategy to disturbance; they produced more byssal threads in microplastic leachate seawater than in control seawater, while motility and aggregation remained essentially unaffected. In contrast, the other two species (M. edulis and Choromytilus meridionalis), showed a resilience strategy to disturbance through increased motility and aggregation in leachate seawater, while byssal thread production remained unaffected. These results suggest that the competitive abilities of intertidal mussels may be related to their sensitivity to microplastic leachates or other chemical disturbance. Importantly, the trait strengthening observed will affect the ability of these mussels to form spatially patterned beds, with implications for their quality as autogenic ecological engineers or foundation species. Thus, our findings have implications for the ability of mussel beds to tolerate disturbance, and hence for central ecosystem services, such as their ability to support biodiversity and enhance secondary and tertiary production. The results suggest that an inconspicuous aspect of plastic pollution has the potential to influence other communities and ecosystems in powerful ways. French Ministere de l'Enseignement Superieur et de la Recherche Hauts de France RegionRegion Hauts-de-France European Funds for Regional Economical Development Pierre Hubert Curien PESSOA Fellowship Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [IF/01413/2014/CP1217/CT0004] National Research Foundation of South AfricaNational Research Foundation - South Africa [64801] South African Research Chairs Initiative (SARChI) of the Department of Science and Technology National FoundationNational Science Foundation (NSF) South African National Research Foundation (NRF)National Research Foundation - South Africa info:eu-repo/semantics/publishedVersion