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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

Through seafood consumption, microplastic (MP) pollution is potentially threatening human health. Commercial bivalves in particular are a cause of major concern because their filter-feeding activity directly exposes them to MP in the water column and they are then ingested by humans. Here, we provide a quantitative and qualitative baseline data on MP content in the soft tissues of three commercially important bivalves (Ruditapes decussatus, Cerastoderma spp. and Polititapes spp.) collected in Ria Formosa lagoon, southern Portugal. The abundance of MPs (items per soft tissue weight) did not significantly differ among species. On average, R. decussatus exhibited the highest MP abundance (on average, 18.4 +/- 21.9 MP items g(-1) WW), followed by Cerastoderma spp. (11.9 +/- 5.5 MP items g(-1) WW) and Polititapes spp. (10.4 +/- 10.4 MP items g(-1) WW). Overall, 88% of the MPs found were synthetic fibres, the majority of which were blue (52%). Size categories >0.1-1 mm and >1-5 mm were the most common (60% and 34% respectively). The most represented polymers were polyethylene (PE) and polystyrene (PS). The unexpectedly high number of MPs recorded in the three commercially exploited species suggests that this semi-closed lagoon system is experiencing a higher anthropogenic pressure than are open coastal systems. Portuguese Foundation for Science and Technology: PTDC/MAR-EST/3223/2014 IF/01413/2014/CP1217/CT0004 UIDB/04326/2020 SFRH/BPD/119344/2016 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

Intertidal mussels are important ecosystem engineers that increase habitat complexity and provide shelter, substratum and food to associated communities. They thus play a key role in the maintenance of local biodiversity. Intertidal mussels are frequently parasitized by endolithic cyanobacteria that erode and significantly weaken their shells. We examined succession of cyanobacterial infestation in the shells of the mussels Perna perna and Mytilus galloprovincialis on the south coast of South Africa. We examined variations in species composition of the endolithic cyanobacterial community across regions of mussel shells of different ages (variation in space) and by exposing non-infested shells in field experiments for known periods (variation in time). The results on the spatial distribution of endolith species within a shell supported those from the field experiment evaluating temporal succession. Endolithic species that were early colonists of clean shells were similar to those that were found at the distal edge, the new and growing region of the shell. These species were also found near the umbo, the oldest region of the shell, but cyanobacterial communities near the umbo also included species that appeared late in time. Thus, succession when viewed in either time or space involved the accumulation, rather than the replacement of species. Species that arrived late in the succession were similar to endolithic species found near the umbo, the oldest region of the shell. Overall, the study shows clear patterns of endolithic cyanobacterial succession within mussel shells.

Anthropogenic litter is ubiquitous throughout marine ecosystems, but its abundance and distribution are driven by complex interactions of distinct environmental factors and thus can be extremely heterogeneous. Here we compare the extent of anthropogenic litter pollution at a sheltered lagoon habitat and nearby open coast sites. Monthly surveys over a period of five months showed that both the types and sources of litter always differed significantly between lagoon and open coast sites. Pollution within the lagoon was mainly land-derived and was largely made up of construction materials (70% to 95%). At open coast sites, construction materials represented a minor portion of pollution (4% to 12%) while plastics were the most abundant (82% to 95%). We show that stranded anthropogenic litter in adjacent marine habitats can differ significantly and stress the importance of sampling at appropriate spatial scales to gain realistic insights into the sources of pollution. Fundacao para a Ciencia e a Tecnologia (FCT - MEC, Portugal) [IF/01413/2014/CP1217/CT0004, UIDB/Multi/04326/2020] National Research Foundation of South AfricaNational Research Foundation - South Africa [64801] info:eu-repo/semantics/publishedVersion

Understanding the spread of invasive species in many regions is difficult because surveys are rare. Here, historical records of the invasive marine mussel, Semimytilus algosus, on the shores of Angola and Namibia are synthesised to re-construct its invasive history. Since this mussel was first discovered in Namibia about 90 years ago, it has spread throughout the western coast of southern Africa. By the late 1960s, the species was well established across a range of 1005 km of coastline in southern Angola and northern Namibia. Although only coarse spatial resolution data are available since the 1990s, the distribution of S. algosus clearly increased substantially over the subsequent decades. Today, the species is distributed over 2785 km of coastline, appearing in southern Namibia in 2014, whence it spread across the border to northern South Africa in 2017, and in northern Angola in 2015. Conspicuously, its current range appears to be relatively contiguous across at least 810 km of shore in southern Angola and throughout Namibia, with isolated, spatially disjunct occurrences towards the southern and northern limits of its distribution. Despite there being few occurrence records that are unevenly distributed spatially and temporally, data for the distributional patterns of S. algosus in Angola and Namibia provide invaluable insights into how marine invasive species spread in developing regions that are infrequently monitored.

Upwelling strongly influences the composition and dynamics of coastal communities by affecting species abundances, recruitment, dispersal and distribution. Coastal upwelling areas are key model regions to study the responses of coastal species to climate change because they are characterized by cooler water conditions and experience lower warming rates than adjacent regions, making them effective 'control' or refuge sites. This is particularly true for the benthic species of rocky shores in upwelling areas because they are sedentary, inhabit the interface between marine and terrestrial habitats, are exposed to extremely severe and variable environmental conditions and often live near their tolerance limits. We sampled roughly 2000 km of the Atlantic coast of Morocco and Western Sahara to assess the influence of upwelling cells on patterns of diversity and abundance of northern African rocky shore species. We recorded 186 taxa, providing clarification of the distribution of 141 algae and documenting nine new species records for Morocco and Western Sahara. The results emphasize the influence of upwelling on the abundance and distribution of these organisms. The contrast between non-upwelling and upwelling areas highlights the direct and indirect importance of water temperature in shaping these communities, pointing to the consequences of large-scale warming. Such warming is likely to threaten intertidal species that already live close to their thermal tolerance limits and are not buffered by the effects of upwelling. Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2019, IF/01413/2014/CP1217/CT0004] National Research Foundation of South AfricaNational Research Foundation - South Africa [64801] Programme Science without Borders (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, of the Ministry of Science, Technology and Innovation of Brazil) [237998/2012-2] info:eu-repo/semantics/publishedVersion

Marine litter is widely dispersed throughout coastal environments. Assessing the distribution and accumulation of such contaminants is crucial to understand their environmental impacts. This study presents a baseline for the monitoring of litter and microplastics in intertidal sediments along the Atlantic shores of southern Portugal and Morocco and identifies potential sources of contamination. Although variable, distribution and composition of both litter and microplastics did not follow a latitudinal pattern. Most of the litter had an undifferentiated source. Within the identifiable sources of litter, food packaging, fishing and tobacco were the most abundant, with variable contributions among sites. Over 97% of marine litter retrieved was plastic. Fragments and filaments were the most abundant categories of plastics at sites with the highest and lowest microplastic abundance respectively. Filaments were mainly made of Polypropylene (PP,50%) and Polyethylene terephthalate (PET,29%) while the predominant polymers for fragments were Polyethene (PE, 75%) and PP (25%). Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2019, IF/01413/2014] South African Research Chairs Initiative (SARChI) of the Department of Science and Technology [64801]

Excessive use of plastics in daily life and the inappropriate disposal of plastic products are severely affecting wildlife species in both coastal and aquatic environments. Birds are top-predators, exposed to all threats affecting their environments, making them ideal sentinel organisms for monitoring ecosystems change. We set a baseline assessment of the prevalence of marine plastic litter affecting multi-species populations of aquatic birds in southern Portugal. By examining 160 stomach contents from 8 species of aquatic birds, we show that 22.5% were affected by plastic debris. Plastic was found in Ciconia ciconia, Larus fuscus and L. michahellis. Ciconia ciconia ingested the highest amount (number of items and total mass) of plastic debris. Polydimethylsiloxane (PDMS, silicones) was the most abundant polymer and was recorded only in C. ciconia. Plastic ingestion baseline data are of crucial importance to evaluate changes through time and among regions and to define management and conservation strategies.

Ecosystems often face a complex combination of natural and anthropogenic disturbances. The assessment of anthropogenic pressures and co-occurring natural stressors is crucial to our understanding of ecosystem structures, dynamics and their conservation. The present study provides the first experimental assessment of the combined effects of trampling (anthropogenic stressor) and endolithic induced erosion (natural stressor) on two coexisting intertidal mussel species, Mytilus galloprovincialis (de Lamarck, 1819) and Perna perna (Linnaeus, 1758). Mixed beds of the two species experiencing a wide range of endolithic parasitation were exposed to increasing intensities of human trampling. Our results clearly show that endolith-infested mussels are more vulnerable to trampling than non-infested individuals. At high trampling intensities, P. perna suffered significantly lower mortalities rates than M. galloprovincialis. More than 20% of large, infested M. galloprovincialis individuals were crushed even at low trampling intensities. Unexpectedly, mortalities rates decreased with mussel size, suggesting a sheltering role of larger conspecifics. Beyond ecological interest, such findings can provide critical experimental support for conservation and management actions. Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2013, IF/01413/2014/CP1217/CT0004] South African Research Chairs Initiative (SARChI) of Department of Science and Technology (DST) National Research Foundation (NRF)

The effects of environmental changes on species distribution are generally studied at large geographical scales. However, aggregations of individuals can significantly moderate the impact of the environment at smaller, organismal scales. We focused on the intertidal macroalga Fucus guiryi and carried out field and laboratory common garden experiments to evaluate how the different individual morphologies and canopy densities typical of central and peripheral populations modify microhabitat conditions and associated levels of stress. We show that F. guiryi canopies significantly alter environmental conditions (i.e., temperature, humidity and light regimes) and mitigate the levels of stress experienced by individuals within the group. Southern algae are more branched and form denser canopies but, unexpectedly, despite these considerable differences, the mitigating effects of northern and southern canopies did not differ significantly. Microhabitat conditions beneath canopies were more stressful at marginal locations, indicating that southern populations are not more effective than northern algae at mitigating the harsher climate at the edge of the species distribution. Our findings highlight the importance of assessing structural changes in aggregating species across their distribution and relating these to local climates to understand the impact of environmental changes at scales relevant to individual organisms. Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2013, IF/01413/2014/CP1217/CT0004] South African Research Chairs Initiative (SARChI) of the Department of Science and Technology National Research Foundation

By altering the phenotypic properties of their hosts, endolithic parasites can modulate the engineering processes of marine ecosystem engineers. Here, we assessed the biogeographical patterns of species assemblages, prevalence and impact of endolithic parasitism in two mussel species that act as important ecosystem engineers in the southern African intertidal habitat, Perna perna and Mytilus galloprovincialis. We conducted large-scale surveys across three biogeographic regions along the South African coast: the subtropical east coast, dominated by the indigenous mussel, P. perna, the warm temperate south coast, where this species coexists with the invasive Mediterranean mussel, M. galloprovincialis, and the cool temperate west coast dominated by M. galloprovincialis. Infestation increased with mussel size, and in the case of M. galloprovincialis we found a significantly higher infestation in the cool temperate bioregion than the warm temperate region. For P. perna, the prevalence of infestation was higher on the warm temperate than the subtropical region, though the difference was marginally non-significant. On the south coast, there was no significant difference in infestation prevalence between species. Endolith-induced mortality rates through shell collapse mirrored the patterns for prevalence. For P. perna, endolith species assemblages revealed clear grouping by bioregions. Our findings indicate that biogeography affects cyanobacteria species composition, but differences between biogeographic regions in their effects are driven by environmental conditions. Agência financiadora Número do subsídio Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) UID/Multi/04326/2019 IF/01413/2014/CP1217/CT0004 South African Research Chairs Initiative (SARChI) of the Department of Science and Technology National Research Foundation info:eu-repo/semantics/publishedVersion

In modem society, plastic items have become indispensable. The rapid growth of plastic production has led to an increase in the concentration of plastic waste in the environment and, consequently, wildlife has been severely affected. As wide-ranging foragers and predators, aquatic birds are ideal sentinels for monitoring changes in their environment. Plastic found in stomach contents of stranded aquatic birds collected throughout Portugal was examined. Out of the 288 birds processed, 12.9% ingested plastics. Six of the 16 species assessed showed evidence of plastic ingestion. The Lesser Black-backed Gull (18.7%) had the highest incidence while, among those that did ingest plastics, the Northern Gannet (4.8%) had the lowest. User plastics were the most common type of plastic ingested, while microplastics and off/white-clear were the most common size and colour respectively of plastics found. This study sets a first multispecies baseline for incidence of plastic ingestion by aquatic birds in Portugal. Fundacao para a Ciencia e a Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2013, IF/01413/2014] 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

Aim Although many studies have reported the effects of climate change on species' distributions, most of them consider each species as a physiologically homogenous unit. However, different lineages or populations inhabiting distinct bioregions within a species' distributional range can retain unique genetic diversity that could result in distinct adaptive capacities. A recent, large, climate-correlated distributional range contraction occurred at the southern edge of the intertidal macroalga Fucus vesiculosus, causing loss of genetic diversity unique to the southern clade. We tested for differential selective constraints and signs of local adaptation to thermal stress in the two genetic lineages. Location Iberian Atlantic shores. Methods We performed a series of common garden experiments and a field reciprocal transplant. Results In the laboratory, southern F. vesiculosus showed higher resilience to heat stress than northern individuals. On the southwest coast of Portugal, local individuals grew more than those transplanted from the northern range; in the north of Portugal, growth rates did not differ significantly between lineages. Conclusions We present evidence for unique adaptive traits at the retreating edge of the species' distribution that could be lost if warming trends persist. The loss of the distinct southern genetic heritage could end potential ongoing diversification or speciation processes and impoverishes the adaptive potential of the species as a whole.

We report the development of nine polymorphic microsatellite markers for Corallina officinalis (Linnaeus, 1758), a calcifying intertidal red alga and important ecosystem engineer spread along the North East Atlantic. Characterization and analysis of loci were made using 15 individuals of C. officinalis from populations in Iceland and the UK. The average number of alleles per locus was 3.78 (range 2-6) and mean of gene diversity was 0.58 (range 0.38-0.77). The set of microsatellites developed here will provide a useful molecular tool for population genetic and conservation studies.

Oceanographic features shape the distributional and genetic patterns of marine species by interrupting or promoting connections among populations. Although general patterns commonly arise, distributional ranges and genetic structure are species-specific and do not always comply with the expected trends. By applying a multimarker genetic approach combined with Lagrangian particle simulations (LPS) we tested the hypothesis that oceanographic features along northeastern Atlantic and Mediterranean shores influence dispersal potential and genetic structure of the intertidal mussel Perna perna. Additionally, by performing environmental niche modelling we assessed the potential and realized niche of P. perna along its entire native distributional range and the environmental factors that best explain its realized distribution. Perna perna showed evidence of panmixia across > 4,000 km despite several oceanographic breaking points detected by LPS. This is probably the result of a combination of life history traits, continuous habitat availability and stepping-stone dynamics. Moreover, the niche modelling framework depicted minimum sea surface temperatures (SST) as the major factor shaping P. perna distributional range limits along its native areas. Forthcoming warming SST is expected to further change these limits and allow the species to expand its range polewards though this may be accompanied by retreat from warmer areas. Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2013, IF/01413/2014/CP1217/CT0004]; South African Research Chairs Initiative (SARChI) of the Department of Science and Technology; National Research Foundation; South African National Research Foundation (NRF); Portuguese Fundacao para a Ciencia e Tecnologia (FCT) [SFRH/BPD/85040/2012, SFRH/BPD/111003/2015] info:eu-repo/semantics/publishedVersion

Aggregations of organisms commonly benefit their members by mitigating the effects of predators and environmental stresses. Mussel aggregations also form important intertidal matrices that support associated infaunal communities, the structures of which are largely shaped by the conditions within the interstitial spaces. Intertidal mussels are frequently parasitized by phototrophic endoliths that infest the shell and have thermoregulatory effects on both solitary and aggregated mussels by changing shell albedo. A large-scale sampling was carried out May June 2016 along Portuguese and Moroccan shores to investigate a latitudinal gradient of endolithic infestation of the intertidal mussel Mytilus galloprovincialis. Endolithic infestation increased towards lower latitudes most likely as a response of greater light availability. Additionally, artificial beds of either 100% non-infested or infested biomimetic mussels were used to test whether infestation alters the temperature and humidity of the interstitial spaces within beds, and if mussels surrounded by infested mussels experience lower body temperatures than those surrounded by non-infested ones. Conditions within beds of infested mussels were significantly cooler and more humid than in non-infested beds and individuals in the centre of infested mussel beds experienced significantly lower body temperatures. Under a scenario of warming climate, endolithic infestation of mussel beds might thus represent an ecological advantage not only for M. galloprovincialis as a species but also for the associated communities. Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2013, IF/01413/2014/CP1217/CT0004] South African Research Chairs Initiative (SARChI) of the Department of Science and Technology National Research Foundation South African National Research Foundation (NRF) info:eu-repo/semantics/publishedVersion

Geographical discontinuities in the composition of species assemblages are often mirrored by genetic clines and local adaptation in species that extend across such biogeographic disjunction. Species distributed across such biogeographic discontinuities are thus more prone to develop genetic clines and adaptations to environmental variation. The northwest coast of France encompasses a biogeographic boundary between cold- and warm-temperate marine ecosystems. Distinct hydrographic features characterize northern and southern shores, promoting physical oceanographic breaks that can affect dispersal and connectivity between populations. Furthermore, mosaics of contrasting conditions may affect local patterns of species assemblages and potential adaptive pressures. Along this stretch of coast, the intertidal habitat is largely dominated by brown algae of the genus Fucus, key structuring species common along North Atlantic shorelines. Fucus spiralis, F. guiryi and F. vesiculosus are sister species with different mating systems. They have extensive sympatric geographical distributions and distinct but overlapping vertical distributions in the intertidal zone. We examined genetic structure and diversity across this major environmental transition zone using neutral microsatellite markers to investigate patterns of differentiation between populations of each species inhabiting the two different biogeographic regions. We found contrasting results between the dioecious species (F. vesiculosus) and the two selfing hermaphroditic lineages (F. spiralis and F. guiryi). Genetic differentiation of northern and southern populations of F. vesiculosus followed the expectation from a hypothetical oceanographic discontinuity across this biogeographical transition zone, but this was not the case for the two hermaphroditic species. The former had higher genetic diversity and structure along the distribution range investigated whereas selfing hermaphrodites had less variability and were not geographically structured. Our results suggest that genetic patterns are correlated with this biogeographical transition zone but this effect is dependent on mating system, a determining factor affecting population structure. Additionally, other factors such as intertidal elevation may also play a role in observed difference in genetic structuring. Fundacao para a Ciencia e a Tecnologia (FCT-MEC, Portugal) [CCMAR - UID/MULTI/04326/2013, EXCL/AAG-GLO/0661/2012, IF/01413/2014/CP1217/CT0004] info:eu-repo/semantics/publishedVersion

Positive and negative aspects of species interactions can be context dependant and strongly affected by environmental conditions. We tested the hypothesis that, during periods of intense heat stress, parasitic phototrophic endoliths that fatally degrade mollusc shells can benefit their mussel hosts. Endolithic infestation significantly reduced body temperatures of sun-exposed mussels and, during unusually extreme heat stress, parasitised individuals suffered lower mortality rates than non-parasitised hosts. This beneficial effect was related to the white discolouration caused by the excavation activity of endoliths. Under climate warming, species relationships may be drastically realigned and conditional benefits of phototrophic endolithic parasites may become more important than the costs of infestation.

AimGlobal climate change has profound and diverse effects on biological diversity. Identifying present-day climate refugia is an increasingly recognized strategy for the management of biodiversity loss. Such refugia are potential safe havens that enhance environmental diversity by buffering the effects of large scale change, facilitating species persistence at regional scales and conserving unique genetic diversity. Although their ecological effects are well studied, the potential of upwelling centres to act as refugia in a scenario of climate warming remains largely unexplored. Here, we investigate whether upwelled waters act as refugia in a region heavily affected by recent climatic changes.LocationShores of south-western Iberia and north-western Africa.MethodsWe compared changes in distribution of the canopy-forming macroalga Fucus guiryi with sea surface temperature patterns in five upwelling areas and adjacent warmer regions. Population diversity and structure was inferred from genotypic analyses using nine microsatellite loci.ResultsFucus guiryi has disappeared from large expanses of non-upwelling shores, currently persisting in areas characterized by strong upwelling and reduced or non-significant rates of warming. Populations of F. guiryi were more abundant towards upwelling centres. Furthermore, the genetic characterization of populations revealed distinct genetic groups associated with each upwelling system.Main conclusionsWithin a large region of predominantly changing climate, we highlight the fundamental importance of upwelling areas as favourable, comparatively stable climates where F. guiryi has retreated and persists, preserving unique portions of the species' genetic pool.

At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10–30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0–2.5 °C, during daily fluctuations that often exceeded 15°–20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on ‘habitat-level’ measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature.

Retracing the origins of invasive species is a first critical step in identifying potential mechanisms of introduction, implementation of management strategies and forecasting the spread of the invader. Mytilus galloprovincialis is an intertidal mussel that is widely distributed in many temperate and subtropical regions. It is invasive worldwide and the most successful invasive marine species in southern Africa. Previous studies have examined genetic relationships between a few South African populations from the south-western coast and other worldwide populations, presenting evidence of a north-eastern Atlantic origin of the invasion. Here, a combination of nuclear (Me15/16 PCR-based) and mitochondrial (16S restriction fragment-length polymorphism; 16S RFLP) DNA assays was applied to infer the origin of this strong invader across its entire southern African distribution (South Africa and Namibia). The 16S RFLP confirmed the northern hemisphere as being the likely sole source of invasion. Additionally, the frequencies of haplotypes at the 16S marker and alleles at the Me15/16 locus point to north-eastern Atlantic shores as the most likely origin throughout the Namibian and South African distribution of the species.

Background Intraspecific variability is seen as a central component of biodiversity. We investigated genetic differentiation, contemporary patterns of demographic connectivity and intraspecific variation of adaptive behavioural traits in two lineages of an intertidal mussel (Perna perna) across a tropical/subtropical biogeographic transition. Results Microsatellite analyses revealed clear genetic differentiation between western (temperate) and eastern (subtropical/tropical) populations, confirming divergence previously detected with mitochondrial (COI) and nuclear (ITS) markers. Gene flow between regions was predominantly east-to-west and was only moderate, with higher heterozygote deficiency where the two lineages co-occur. This can be explained by differential selection and/or oceanographic dynamics acting as a barrier to larval dispersal. Common garden experiments showed that gaping (periodic closure and opening of the shell) and attachment to the substratum differed significantly between the two lineages. Western individuals gaped more and attached less strongly to the substratum than eastern ones. Conclusions These behavioural differences are consistent with the geographic and intertidal distributions of each lineage along sharp environmental clines, indicating their strong adaptive significance. We highlight the functional role of diversity below the species level in evolutionary trends and the need to understand this when predicting biodiversity responses to environmental change. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0366-5) contains supplementary material, which is available to authorized users.

Global climate change is correlated not only with variation in extinction rates, but also with speciation rates. However, few mechanisms have been proposed to explain how climate change may have driven the emergence of new evolutionary lineages that eventually became distinct species. Here, we discuss a model of range extension followed by divergence, in which the same climate oscillations that resulted in the extinction of coastal species across the Atlantic/Indian Ocean boundary in southwestern Africa also sowed the seeds of new biodiversity. We present evidence for range extensions and evolutionary divergence from both fossil and genetic data, but also point out the many challenges to the model that need to be addressed before its validity can be accepted.

By associating closely with others to form a group, an animal can benefit from a number of advantages including reduced risk of predation, amelioration of environmental conditions, and increased reproductive success, but at the price of reduced resources. Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism. Here we show that very simple behaviour in intertidal mussels shows new effects in dense aggregations but not in isolated individuals. Perna perna and Mytilus galloprovincialis are gaping (periodic valve movement during emersion) and non-gaping mussels respectively. P. perna gaping behaviour had no effect on body temperatures of isolated individuals, while it led to increased humidity and decreased temperatures in dense groups (beds). Gaping resulted in cooler body temperatures for P. perna than M. galloprovincialis when in aggregations, while solitary individuals exhibited the highest temperatures. Gradients of increasing body temperature were detected from the center to edges of beds, but M. galloprovincialis at the edge had the same temperature as isolated individuals. Furthermore, a field study showed that during periods of severe heat stress, mortality rates of mussels within beds of the gaping P. perna were lower than those of isolated individuals or within beds of M. galloprovincialis, highlighting the determinant role of gaping on fitness and group functioning. We demonstrate that new effects of very simple individual behaviour lead to amelioration of abiotic conditions at the aggregation level and that these effects increase mussel resistance to thermal stress.

Background Significant effects of recent global climate change have already been observed in a variety of ecosystems, with evidence for shifts in species ranges, but rarely have such consequences been related to the changes in the species genetic pool. The stretch of Atlantic coast between North Africa and North Iberia is ideal for studying the relationship between species distribution and climate change as it includes the distributional limits of a considerable number of both cold- and warm-water species. We compared temporal changes in distribution of the canopy-forming alga Fucus vesiculosus with historical sea surface temperature (SST) patterns to draw links between range shifts and contemporary climate change. Moreover, we genetically characterized with microsatellite markers previously sampled extinct and extant populations in order to estimate resulting cryptic genetic erosion. Results Over the past 30 years, a geographic contraction of the southern range edge of this species has occurred, with a northward latitudinal shift of approximately 1,250 km. Additionally, a more restricted distributional decline was recorded in the Bay of Biscay. Coastal SST warming data over the last three decades revealed a significant increase in temperature along most of the studied coastline, averaging 0.214°C/decade. Importantly, the analysis of existing and extinct population samples clearly distinguished two genetically different groups, a northern and a southern clade. Because of the range contraction, the southern group is currently represented by very few extant populations. This southern edge range shift is thus causing the loss of a distinct component of the species genetic background. Conclusions We reveal a climate-correlated diversity loss below the species level, a process that could render the species more vulnerable to future environmental changes and affect its evolutionary potential. This is a remarkable case of genetic uniqueness of a vanishing cryptic genetic clade (southern clade).