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To project how ocean acidification will impact biological communities in the future, it is critical to understand the potential for local adaptation and the physiological plasticity of marine organisms throughout their entire life cycle, as some stages may be more vulnerable than others. Coralline algae are ecosystem engineers that play significant functional roles in oceans worldwide and are considered vulnerable to ocean acidification. Using different stages of coralline algae, we tested the hypothesis that populations living in environments with higher environmental variability and exposed to higher levels of pCO2 would be less affected by high pCO2 than populations from a more stable environment experiencing lower levels of pCO2. Our results show that spores are less sensitive to elevated pCO2 than adults. Spore growth and mortality were not affected by pCO2 level; however, elevated pCO2 negatively impacted the physiology and growth rates of adults, with stronger effects in populations that experienced both lower levels of pCO2 and lower variability in carbonate chemistry, suggesting local adaptation. Differences in physiological plasticity and the potential for adaptation could have important implications for the ecological and evolutionary responses of coralline algae to future environmental changes.

Summary One of the central questions in evolutionary ecology is how different functional capacities impact fitness, and how it varies across populations. For instance, do phenotypic attributes influence fitness similarly across geographic gradients? Which traits (physiological, morphological and life history) are most likely to be targets of natural selection? Do particular combinations of traits maximize fitness? In a semi‐natural experiment, we analysed introduced populations of an invasive species, the garden snail (Cornu aspersum) in Chile, which show low levels of genetic differentiation in spite of the distance. Specifically, we addressed whether the magnitude, sign and form of selection in snail populations could explain the differentiation (or its absence) among populations. A common garden/reciprocal transplant experiment was performed in three populations (La Serena, Constitución and Valdivia) that span a 1300‐km latitudinal gradient and differ markedly in climate (semi‐arid north to humid south). We released c. 450 individuals per population (two generations after field‐captured snails) in replicated enclosures at the range extremes (La Serena and Valdivia). Morphological (size and shell darkness), physiological (standard metabolic rate and digestive efficiency) and life‐history [growth rate (GR)] traits were measured in all snails before the release. Survival was recorded monthly during 1 year. Survival was significantly higher in snails from La Serena than in snails from Constitución and Valdivia, when raised at La Serena. However, at Valdivia, survival was not different among source populations. Interestingly, we found negative correlational selection in MB and SMRR at La Serena, whereas at Valdivia we only found directional selection on GR and MB, and stabilizing selection on SMRR. These results suggest that selection on physiological traits related with energy allocation is pervasive, irrespective of climate and distance. Lay Summary

In echinoderms, major morphological transitions during early development are attributed to different genetic interactions and changes in global expression patterns that shape the regulatory program for the specification of embryonic territories. In order more thoroughly to understand these biological and molecular processes, we examined the transcriptome structure and expression profiles during the embryo‐to‐larva transition of a keystone species, the giant red sea urchin Mesocentrotus franciscanus. Using a de novo assembly approach, we obtained 176,885 transcripts from which 60,439 (34%) had significant alignments to known proteins. From these transcripts, ~80% were functionally annotated allowing the identification of ~2,600 functional, structural, and regulatory genes involved in developmental process. Analysis of expression profiles between gastrula and pluteus stages of M. franciscanus revealed 791 differentially expressed genes with 251 GO overrepresented terms. For gastrula, up‐regulated GO terms were mainly linked to cell differentiation and signal transduction involved in cell cycle checkpoints. In the pluteus stage, major GO terms were associated with phosphoprotein phosphatase activity, muscle contraction, and olfactory behavior, among others. Our evolutionary comparative analysis revealed that several of these genes and functional pathways are highly conserved among echinoids, holothuroids, and ophiuroids. In echinoderms, major morphological transitions during early development are attributed to different genetic interactions and changes in global expression patterns that shape the regulatory program for the specification of embryonic territories. Here, we examined the transcriptome structure and expression profiles during the embryo‐to‐larva transition of a keystone species, the giant red sea urchin Mesocentrotus franciscanus, exploring questions regarding the level of conservation of orthologous genes and functional pathways among echinoderms. Our analyses revealed important changes in the expression of genes that are thought to contribute in the regulatory program for larval skeletogenesis, endomesodermal, and ectodermal specification of echinoderms. In addition, our evolutionary comparative analysis revealed that several of these genes and functional pathways are highly conserved among echinoids, holothuroids, and ophiuroids.

Potential interactions between marine predators and humans arise in the southern coast of Chile where predator feeding and reproduction sites overlap with fisheries and aquaculture. Here, we assess the potential effects of intensive salmon aquaculture on food habits, growth, and reproduction of a common predator, the spiny dogfish—identified as Squalus acanthias via genetic barcoding. A total of 102 (89 females and 13 males) individuals were collected during winter and summer of 2013–2014 from the Chiloé Sea where salmon aquaculture activities are concentrated. The low frequency of males in our study suggests spatial segregation of sex, while immature and mature females spatially overlapped in both seasons. Female spiny dogfish showed a functional specialist behavior as indicated by the small number of prey items and the relative high importance of the austral hake and salmon pellets in the diet. Immature sharks fed more on pellets and anchovies than the larger hake‐preferring mature females. Our results also indicate that spiny dogfish switch prey (anchovy to hake) to take advantage of seasonal changes in prey availability. Despite differences in the trophic patterns of S. acanthias due to the spatial association with intensive salmon farming, in this region, there appears to be no difference in fecundity or size at maturity compared to other populations. Although no demographic effects were detected, we suggest that a range of additional factors should be considered before concluding that intensive aquaculture does not have any impact on these marine predators. Interactions between marine predators and humans arise in coastal ecosystems in various parts of the world where feeding and reproduction sites overlap with economic activities such as fisheries and aquaculture. Here, we assess the potential effects of intensive salmon aquaculture on food habits, growth, and reproduction of a common predator, the spiny dogfish Squalus acanthias. Our results indicate that the spatial overlap of shark nursery areas and the salmon industry influences the trophic niche of S. acanthias by adding new food items (i.e., pellets; direct effect), and altering the structure and composition of benthic communities (e.g., crustaceans; indirect effect).

Feeding behavior is regulated by a complex network of endogenous neuropeptides. In chordates, this role is suggested to be under the control of diverse factors including thyrotropin-releasing hormone (TRH). However, whether this regulatory activity of TRH is functionally conserved in non-chordate metazoans, and to what extent this process is underpinned by interactions of TRH with other neuropeptides such as cholecystokinin (CCK, known as a satiety signal), remain unclear. This study investigated the TRH signaling system in the echinoderm Apostichopus japonicus. Bioinformatic analyses and ligand-binding assays identified a functional TRH receptor (AjTRHR) that activated signaling via the MAPK/ERK1/2 pathways. Experimental administration of TRH significantly reduced feeding activity, while up-regulating CCK expression. RNA interference (RNAi) experiments confirmed that both CCK and TRH are essential components of satiety signaling, working synergistically to mediate feeding inhibition. Evolutionary analysis of TRH-type peptides revealed greater conservation of the short isoform of TRH compared to the long isoform, probably driven by strong selection acting on the functional redundancy. These findings provide compelling evidence of a TRH-mediated signaling system in non-chordate deuterostomes, expanding our understanding of neuropeptide-regulated feeding mechanisms in marine invertebrates.

Marine multicellular organisms inhabiting waters with natural high fluctuations in pH appear more tolerant to acidification than conspecifics occurring in nearby stable waters, suggesting that environments of fluctuating pH hold genetic reservoirs for adaptation of key groups to ocean acidification (OA). The abundant and cosmopolitan calcifying phytoplankton Emiliania huxleyi exhibits a range of morphotypes with varying degrees of coccolith mineralization. We show that E. huxleyi populations in the naturally acidified upwelling waters of the eastern South Pacific, where pH drops below 7.8 as is predicted for the global surface ocean by the year 2100, are dominated by exceptionally over-calcified morphotypes whose distal coccolith shield can be almost solid calcite. Shifts in morphotype composition of E. huxleyi populations correlate with changes in carbonate system parameters. We tested if these correlations indicate that the hyper-calcified morphotype is adapted to OA. In experimental exposures to present-day vs. future pCO2 (400 vs. 1200 µatm), the over-calcified morphotypes showed the same growth inhibition (-29.1±6.3 %) as moderately calcified morphotypes isolated from non-acidified water (-30.7±8.8 %). Under the high-CO2–low-pH condition, production rates of particulate organic carbon (POC) increased, while production rates of particulate inorganic carbon (PIC) were maintained or decreased slightly (but not significantly), leading to lowered PIC / POC ratios in all strains. There were no consistent correlations of response intensity with strain origin. The high-CO2–low-pH condition affected coccolith morphology equally or more strongly in over-calcified strains compared to moderately calcified strains. High-CO2–low-pH conditions appear not to directly select for exceptionally over-calcified morphotypes over other morphotypes, but perhaps indirectly by ecologically correlated factors. More generally, these results suggest that oceanic planktonic microorganisms, despite their rapid turnover and large population sizes, do not necessarily exhibit adaptations to naturally high-CO2 upwellings, and this ubiquitous coccolithophore may be near the limit of its capacity to adapt to ongoing ocean acidification.

Standard metabolic rate (SMR) and resistance to body dehydration (BD) are important physiological traits that have an effect on water balance and the amount of energy available for activity and production, and thus could contribute to variation in life history traits expressed across a range of environments. Few studies have tested whether SMR and BD show consistent between-individual variation in molluscs. Significant repeatability of SMR and BD indicates that the traits might be heritable and therefore a possible target for natural selection, so describing the repeatability of SMR and BD is important in studies of phenotypic variability. Here, we studied energy metabolism (body mass-corrected SMR) and the change in the scaling relationship of SMR and body mass in response to time between measurements in the giant garden slug Limax maximus. Limax maximus is one of the most invasive terrestrial molluscs, with a wide geographical distribution, and is considered an important pest of horticultural and agricultural crops. Our results show that L. maximus follows the expected relationship of increasing SMR with increasing mass, but the scaling exponent varies through time and is different from that described for other gastropods.We also found significant inter-individual variation in VCO₂ Mean? VCO₂ Min> VCO₂ Max, and BD (τ= 0.25, 0.29, 0.24, 0.22, p< 0.05, respectively), and significant repeatability of body mass (ô= 0.90). To our knowledge, this is the first comprehensive analysis of the repeatability of body mass-corrected SMR and BD in terrestrial slugs. Our results suggest that energy metabolism and water balance could potentially respond to selection.

Aim Understanding how spatio‐temporal environmental variability influences stress tolerance, local adaptation and phenotypic variation among populations is a key challenge for evolutionary ecology and climate change biology. Coastal biogeographic breaks are natural laboratories to explore this fundamental research question due to the contrasting environmental conditions experienced by natural populations across these regions. Location In the South East Pacific (SEP) coast, a major break (30º‐32ºS) is characterized by extreme natural variability in sea surface temperature (SST) and carbonate chemistry parameters related to temporal and spatial dynamics in upwelling events. Calcifying organisms inhibiting this zone are exposed to marked fluctuations and clines in SST that together with naturally acidified waters can impact their metabolism, calcification and fitness, making them particularly prone to the effects of climate change (e.g. ocean acidification, OA). We investigated to what extent the spatial and temporal environmental variability (in SST and seawater carbonate conditions) that characterizes the biogeographic break in the SEP influences intra‐specific differences in the thermal ecology and the tolerances to OA of the limpet Scurria araucana. Methods During two years, we conducted field surveys of limpet populations at sites across the SEP break (27ºS, 30ºS and 32ºS). We collected individuals from each population to test for geographic differences in morphometric (e.g. total buoyancy weight, shell length) and physiological (e.g. oxygen consumption rate, cardiac activity and thermal performance curves; TPC) responses to local environmental conditions (Tº and pH/pCO2) and to simulated OA scenarios. Results Populations of S. Araucana exhibit high tolerance to OA with no signal of geographic influence on this attribute. However, inter‐population differences in thermal physiology (metabolic rates and performances) were found across the biogeographic break in the SEP coast. Limpets from the central part of the break (30ºS) exhibit higher thermal performance compared to limpets from populations at both sides of the break. Main conclusions Variation in SST has a greater effect shaping inter‐population differences in thermal physiology of the limpet S. araucana. These physiological differences are aligned the thermal heterogenous seascape along the biogeographic break in the SEP. Contrarily, temporal and spatial variation in seawater carbonate conditions does not influence inter‐population differences in phenotypic response populations, but an overall high tolerance to OA.

Marine blue mussels (Mytilus spp.) are widespread species that exhibit an antitropical distribution with five species occurring in the Northern Hemisphere ( M. trossulus , M. edulis , M. galloprovincialis , M. californianus and M. coruscus ) and three in the Southern Hemisphere ( M. galloprovincialis , M. chilensis and M. platensis ). Species limits in this group remain controversial, in particular for those forms that live in South America. Here we investigated structural characteristics of marine mussels mitogenomes, based on published F mtDNA sequences of Northern Hemisphere species and two newly sequenced South American genomes, one from the Atlantic M. platensis and another from the Pacific M. chilensis . These mitogenomes exhibited similar architecture to those of other genomes of Mytilus , including the presence of the Atp8 gene, which is missing in most of the other bivalves. Our evolutionary analysis of mitochondrial genes indicates that purifying selection is the predominant force shaping the evolution of the coding genes. Results of our phylogenetic analyses supported the monophyly of Pteriomorphia and fully resolved the phylogenetic relationships among its five orders. Finally, the low genetic divergence of specimens assigned to M. chilensis and M. platensis suggests that these South American marine mussels represent conspecific variants rather than distinct species.

The ability of organisms to perform at different temperatures could be described by a continuous nonlinear reaction norm (i.e., thermal performance curve, TPC), in which the phenotypic trait value varies as a function of temperature. Almost any shift in the parameters of this performance curve could highlight the direct effect of temperature on organism fitness, providing a powerful framework for testing thermal adaptation hypotheses. Inter-and intraspecific differences in this performance curve are also reflected in thermal tolerances limits (e.g., critical and lethal limits), influencing the biogeographic patterns of species' distribution. Within this context, here we investigated the intraspecific variation in thermal sensitivities and thermal tolerances in three populations of the invasive snail Cornu aspersum across a geographical gradient, characterized by different climatic conditions. Thus, we examined population differentiation in the TPCs, thermal-coma recovery times, expression of heat-shock proteins and standard metabolic rate (i.e., energetic costs of physiological differentiation). We tested two competing hypotheses regarding thermal adaptation (the \"hotter is better\" and the generalist-specialist trade-offs). Our results show that the differences in thermal sensitivity among populations of C. aspersum follow a latitudinal pattern, which is likely the result of a combination of thermodynamic constraints (\"hotter is better\") and thermal adaptations to their local environments (generalist-specialist trade-offs). This finding is also consistent with some thermal tolerance indices such as the Heat-Shock Protein Response and the recovery time from chill-coma. However, mixed responses in the evaluated traits suggest that thermal adaptation in this species is not complete, as we were not able to detect any differences in neither energetic costs of physiological differentiation among populations, nor in the heat-coma recovery.