Investigating intraspecific variability in the biological responses of sea urchins (Paracentrotus lividus) to seawater acidification.

Alterations in seawater chemistry posed by acidification may lead to immunological and antioxidant defence impairment in sea urchins, with differences among local populations. Here, we analyzed the effects of reduced pH on Paracentrotus lividus, with a multibiomarker approach, and the possible intraspecific variations in sea urchin responses. Two groups of animals with different ecological histories (i.e., the pattern of environmental characteristics and pressures experienced throughout the organism's lifetime) were maintained at ambient pH and pH reduced of 0.4 units for 8 months. Changes in gonadosomatic index (GSI), immunological, and oxidative stress biomarkers were assessed in coelomic fluid, gonads, and digestive tract. Animals maintained at reduced pH showed limited impact of seawater acidification compared to the ambient pH condition. However, sea urchins from the two sites were differently influenced by the seawater pH (as shown by multivariate analyses). GSI and immunological and antioxidant status were differentially modulated between the two sexes, with generally higher values in females, but differences between sexes in relation to the pH of exposure were limited. Overall, our findings highlight that the impact of environmental stressors may differ in sea urchins from different locations. This has implications for the maintenance of P. lividus wild populations under future global change scenarios.

Stable body sizes in soil nematodes across altitudes: The role of intrageneric variation in community assembly.

Animal body size exhibits rapid responses to environmental variations and displays considerable variability across ecological scales, significantly influencing ecological community assembly. However, our understanding of the extent of body size variation and its responses to environmental differences within soil fauna remains limited, impeding a comprehensive grasp of soil fauna's functional ecology. Here, we aim to investigate the magnitude of intrageneric body size variation and its implications for soil nematode community assembly along an altitudinal gradient. We examined soil nematode body size responses along an altitudinal gradient spanning from 3136 to 4128 m in an alpine mountain region of the eastern Tibetan Plateau. We assessed the contributions of intra- and intergeneric variations in body size, both within and among communities, using individual body size values. The implications of these variations for community assembly processes were determined through phenotypic variance ratios employing permutation tests. Our analyses did not reveal statistically significant correlations between altitude and the community-weighted mean body mass, regardless of considering intrageneric trait variation (IGTV). Approximately 15% of the variation in body size among communities and a substantial 72% of the variation in body size within communities can be attributed to IGTV. Altitude did not significantly affect IGTV within or among communities. Furthermore, our results underscored the dominant role of internal filtering within the community in governing nematode community assembly, with external filtering outside the community playing a limited role within our altitudinal range. Our findings emphasize the dominant role of body size variation within communities rather than among communities, attributable to strong internal filtering processes. These findings advance our understanding of body size variation in soil nematodes across ecological scales and highlight the pivotal role of intrageneric variation in shaping the functional ecology of soil fauna.

Leopard subspecies conservation under climate and land-use change.

Predicting the effects of global environmental changes on species distribution is a top conservation priority, particularly for large carnivores, that contribute to regulating and maintaining ecosystems. As the most widespread and adaptable large felid, ranging across Africa and Asia, leopards are crucial to many ecosystems as both keystone and umbrella species, yet they are threatened across their ranges. We used intraspecific species distribution models (SDMs) to predict changes in range suitability for leopards under future climate and land-use change and identify conservation gaps and opportunities. We generated intraspecific SDMs for the three western leopard subspecies, the African, Panthera pardus pardus; Arabian, Panthera pardus nimr; and Persian, Panthera pardus tulliana, leopards, and overlapped predictions with protected areas (PAs) coverage. We show that leopard subspecies differ in their environmental associations and vulnerability to future changes. The African and Arabian leopards are predicted to lose ~25% and ~14% of their currently suitable range, respectively, while the Persian leopard is predicted to experience ~12% range gains. We found that most areas predicted to be suitable were not protected, with only 4%-16% of the subspecies' ranges falling inside PAs, and that these proportions will decrease in the future. The highly variable responses we found between leopard subspecies highlight the importance of considering intraspecific variation when modelling vulnerability to climate and land-use changes. The predicted decrease in proportion of suitable ranges falling inside PAs threatens global capacity to effectively conserve leopards because survival rates are substantially lower outside PAs due to persecution. Hence, it is important to work with local communities to address negative human-wildlife interactions and to restore habitats to retain landscape connectivity where PA coverage is low. On the other hand, the predicted increase in range suitability across southern Europe presents opportunities for expansion outside of their contemporary range, capitalising on European rewilding schemes.

Seasonality in Crotalus durissus venom.

Rattlesnakes belonging to the genus Crotalus are widely distributed throughout the Americas. In Brazil, symptoms commonly associated with envenomation by Crotalus durissus collilineatus include myalgia, rhabdomyolysis, renal failure, neurotoxicity, and progressive paralysis, which are related to the protein composition of this venom. Snake venom composition exhibits compositional variability that may reflect geographic distribution, age, captivity, diet, sex, and even individual genetics. Although seasonality is also considered a possible source of variation, there are few reports of such variability in snake venom. In this work, venoms of the same eight C. durissus collilineatus were extracted every three months for two years, to analyze seasonal changes in composition and activities. To this end, venom composition was analyzed by protein quantification, SDS-PAGE, and HPLC, and the LAAO, PLA2 and coagulant activities were measured. Venoms of these C. d. collilineatus showed minor seasonal differences in venom activities and no composition differences were found. LAAO and coagulant activities displayed a pattern of seasonal change, while PLA2 activity seemed to have no seasonality tendency. Also, there are sexual differences, in which males seem to be more stable than females in regard to some activities. Individual variability occurs even in seasonal variation of activities, highlighting the importance of controlling circumstances of venom extraction before comparing results between groups of snakes.

Skeletonema marinoi ecotypes show specific habitat-related responses to fluctuating light supporting high potential for growth under photobioreactor light regime.

Diatoms are a diverse group of phytoplankton usually dominating areas characterized by rapidly shifting light conditions. Because of their high growth rates and interesting biochemical profile, their biomass is considered for various commercial applications. This study aimed at identifying strains with superior growth in a photobioreactor (PBR) by screening the natural intraspecific diversity of ecotypes isolated from different habitats. We investigated the effect of PBR light fluctuating on a millisecond scale (FL, simulating the light in a PBR) on 19 ecotypes of the diatom Skeletonema marinoi isolated from the North Sea-Baltic Sea area. We compare growth, pigment ratios, phylogeny, photo-physiological variables and photoacclimation strategies between all strains and perform qPCR and absorption spectra analysis on a subset of strains. Our results show that the ecotypes responded differently to FL, and have contrasting photo-physiological and photoprotective strategies. The strains from Kattegat performed better in FL, and shared common photoacclimation and photoprotection strategies that are the results of adaptation to the specific light climate of the Kattegat area. The strains that performed better with FL conditions had a high light (HL)-acclimated phenotype coupled with unique nonphotochemical quenching features. Based on their characteristics, three strains were identified as good candidates for growth in PBRs.

Defoliation, trampling and nutrient return differentially influence grassland productivity by modulating trait-dependent plant community composition: insights from a simulated grazing experiment.

Ungulate grazing involves multiple components, including defoliation, dung and urine return, and trampling, which supply offsetting or synergistic effects on plant community composition and productivity (ANPP), but these effects have not been fully studied. Plant functional traits may reflect the response of plants to disturbance and their impact on ecosystem functions. Species turnover and intraspecific trait variation (ITV) are important drivers of community trait composition. We conducted a simulated grazing experiment in a steppe grassland in northern China to examine the effects of defoliation, dung and urine return, and trampling on community-weighted mean (CWM), functional diversity (FD) and ANPP, and to disentangle the roles of species turnover and ITV in driving these changes. We found that defoliation had a dominant effect on CWMs and FDs of all four traits through species turnover and ITV, respectively, resulting in a convergence of traits towards as more resource-acquisitive strategy. Dung-urine return resulted in more resource-acquisitive community traits mainly through ITV, whereas there were no significant effects on FDs except for leaf C/N. Trampling increased CWM of leaf dry matter content primarily driven by ITV, and had no significant effect on FDs. Furthermore, our simulated grazing positively affected ANPP, primarily due to nutrient additions from dung and urine, and ITV largely explained the variation in ANPP. These findings highlight the multifaceted effects of grazing components on community structure and ANPP, and the significance of ITV in shaping grassland plant communities and productivity.

Influence of surface water and groundwater on functional traits and trade-off strategies of oasis communities at the end of the Keriya River, China.

Plant functional traits reflect the capacity of plants to adapt to their environment and the underlying optimization mechanisms. However, few studies have investigated trade-off strategies for functional traits in desert-wetland ecosystems, the mechanisms by which surface water disturbance and groundwater depth drive functional trait variation at the community scale, and the roles of intraspecific and interspecific variation. Therefore, this study analyzed specific differences in community-weighted mean traits among habitat types and obtained the relative contribution of intraspecific and interspecific variation by decomposing community-weighted mean traits, focusing on the Daliyabuyi Oasis in the hinterland of the Taklamakan Desert. We also explored the mechanisms by which surface water and groundwater influence different sources of variability specifically. The results showed that plant height, relative chlorophyll content, leaf thickness, leaf nitrogen content, and nitrogen-phosphorus ratio were the key traits reflecting habitat differences. As the groundwater depth becomes shallower and surface water disturbance intensifies, plant communities tend to have higher leaf nitrogen content, nitrogen-phosphorus ratio, and relative chlorophyll content and lower height. Surface water, groundwater, soil water content, and total soil nitrogen can influence interspecific and intraspecific variation in these traits through direct and indirect effects. As arid to wet habitats change, plant trade-off strategies for resources will shift from conservative to acquisitive. The study concluded that community functional traits are mainly contributed by interspecific variation, but consideration of intraspecific variation and the covariation effects that exist between it and interspecific variation can help to further enhance the understanding of the response of community traits in desert-wetland ecosystems to environmental change. Surface water disturbance has a non-negligible contribution to this adaptation process and plays a higher role than groundwater depth.

Effects of microhabitat features on the intraspecific variability of the distribution and functional traits in a highest elevational distributed lizard.

Exploring the microhabitat determinants of organisms distribution and functional traits differences can help us better understand the importance of intraspecific variations in ecological niches. Investigations on animals functional niche primarily focused on differences among species and tended to neglect the potential variability within species, despite the fact that the ecological and evolutionary importance of intraspecific variations was widely recognized. In this study, we examined the influence of microhabitat features on the intraspecific variability of the distribution and functional traits of a highest elevational distributed lizard species Phrynocephalus erythrurus. To do so, field work was conducted between July and August, 2020 and August and September, 2021 in Namtso watershed in central Xizang, China. Specifically, 11 transects were sampled for P. erythrurus individuals, which were measured for a set of 10 morphological traits. Moreover, 11 microhabitat variables that potentially affect the distribution of lizards were also measured for each transect. Our results indicated that juveniles, males, and females exhibited different functional traits, allowing them to occupy distinct functional space. The distribution of juveniles, males, and females was determined by different microhabitat variables such as illuminance and air temperature. More importantly, these variables also determined the intraspecific functional traits variability in this lizard species. All of these results supported previous claims that intraspecific traits variation should be incorporated into functional ecological studies, and diverse microhabitat features should be conserved to maintain high intraspecific diversity. Future studies can focus on the food analysis to explore the linkage between functional traits and resources utilization within animal populations.

Seasonality in Crotalus durissus venom

Rattlesnakes belonging to the genus Crotalus are widely distributed throughout the Americas. In Brazil, symptoms commonly associated with envenomation by Crotalus durissus collilineatus include myalgia, rhabdomyolysis, renal failure, neurotoxicity, and progressive paralysis, which are related to the protein composition of this venom. Snake venom composition exhibits compositional variability that may reflect geographic distribution, age, captivity, diet, sex, and even individual genetics. Although seasonality is also considered a possible source of variation, there are few reports of such variability in snake venom. In this work, venoms of the same eight C. durissus collilineatus were extracted every three months for two years, to analyze seasonal changes in composition and activities. To this end, venom composition was analyzed by protein quantification, SDS-PAGE, and HPLC, and the LAAO, PLA2 and coagulant activities were measured. Venoms of these C. d. collilineatus showed minor seasonal differences in venom activities and no composition differences were found. LAAO and coagulant activities displayed a pattern of seasonal change, while PLA2 activity seemed to have no seasonality tendency. Also, there are sexual differences, in which males seem to be more stable than females in regard to some activities. Individual variability occurs even in seasonal variation of activities, highlighting the importance of controlling circumstances of venom extraction before comparing results between groups of snakes.

Fine Structure of the Mouthparts of Three Tomicus Beetles Co-Infecting Pinus yunnanensis in Southwestern China with Some Functional Comments.

Tomicus yunnanensis, T. brevipilosus, and T. minor are the most economically significant pests of Pinus yunnanensis in Southwestern China. Chemical and physical factors play critical roles in diverse biological activities. Here, we describe the fine structure of the adult mouthparts of these three Tomicus species using scanning and transmission electron microscopy. We identified three types of mandibular shapes, which determine their biomechanical properties, their ability to process food, and their preferred foraging locations on tree trunks. Eleven types of sensilla were discernible, including sensilla basiconica (Sb.1-2), sensilla twig basiconica (Stb.1-3), sensilla coeloconica (Sco), sensilla chaetica (Sch.1-2), sensilla trichoidea (Str.1-2), and sensilla digitiformia (Sdi). Each basiconic sensillum occurs on the palpal tips and is innervated by 2-6 dendrites. Sb.1 are gustatory receptors, Sb.2 are olfactory receptors, and the three other sensilla have dual taste and mechanical functions. Sco, Sch, and Str are mechanoreceptors. Sdi are mechanical vibration receptions, given that they are innervated by one dendrite with numerous dendritic branches into the nonporous cuticle. No significant differences among the sexes or species were identified; however, intraspecific variability in the number of Stb.3 and Sdi sensilla was evident. These results will aid future studies of Tomicus beetle behaviors.

Linking functional composition moments of the sub-Mediterranean ecotone with environmental drivers.

Introduction: Functional trait-based approaches are extensively applied to the study of mechanisms governing community assembly along environmental gradients. These approaches have been classically based on studying differences in mean values among species, but there is increasing recognition that alternative metrics of trait distributions should be considered to decipher the mechanisms determining community assembly and species coexistence. Under this framework, the main aim of this study is to unravel the effects of environmental conditions as drivers of plant community assembly in sub-Mediterranean ecotones. Methods: We set 60 plots in six plant communities of a sub-Mediterranean forest in Central Spain, and measured key above- and belowground functional traits in 411 individuals belonging to 19 species, along with abiotic variables. We calculated community-weighted mean (CWM), skewness (CWS) and kurtosis (CWK) of three plant dimensions, and used maximum likelihood techniques to analyze how variation in these functional community traits was driven by abiotic factors. Additionally, we estimated the relative contribution of intraspecific trait variability and species turnover to variation in CWM. Results and discussion: The first three axes of variation of the principal component analyses were related to three main plant ecological dimensions: Leaf Economics Spectrum, Root Economics Spectrum and plant hydraulic architecture, respectively. Type of community was the most important factor determining differences in the functional structure among communities, as compared to the role of abiotic variables. We found strong differences among communities in their CWMs in line with their biogeographic origin (Eurosiberian vs Mediterranean), while differences in CWS and CWK indicate different trends in the functional structure among communities and the coexistence of different functional strategies, respectively. Moreover, changes in functional composition were primarily due to intraspecific variability. Conclusion: We observed a high number of strategies in the forest with the different communities spreading along the acquisitive-conservative axis of resource-use, partly matching their Eurosiberian-Mediterranean nature, respectively. Intraspecific trait variability, rather than species turnover, stood as the most relevant factor when analyzing functional changes and assembly patterns among communities. Altogether, our data support the notion that ecotones are ecosystems where relatively minor environmental shifts may result in changes in plant and functional composition.

First record of Colpodidium caudatum (Ciliophora, Colpodidiidae) in Europe.

The present study documents the discovery of the first European population of Colpodidium caudatum (Ciliophora, Colpodidiidae) in a water drain in a school playground in Manzanares (Ciudad Real, Spain). This species has been documented on every continent except Antarctica and Europe, until now. The ciliate was isolated from wet run-off soil collected from the water drain and was grown in semi-permanent cultures in the laboratory. The infraciliature of the ciliate was revealed using silver carbonate impregnation and cell measurements were taken from living and silver-impregnated specimens. A comparative analysis of published data from various populations of C. caudatum across the globe showed high intraspecific morphological variability in this species. To differentiate between species within the Colpodidium genus, a dichotomous key is presented. This investigation shows that C. caudatum is a ciliate that is found all over the world and is particularly associated with terrestrial habitats that are periodically flooded.

Living at the edge: the functional niche occupation of woody plant communities in the submediterranean ecotone.

BACKGROUND AND AIMS: Submediterranean areas are rich ecotones, where slight modifications in environmental conditions can lead to substantial changes in the composition of plant communities. They thus offer an ideal scenario to examine plant community assembly. In this study, we followed a trait-based approach including intraspecific variability to elucidate (1) the relationship between niche occupancy components and species richness, (2) the processes governing the assembly of these communities and (3) the contribution of intraspecific trait variability in shaping the functional trait space. METHODS: We measured eight morphological and chemical traits in 405 individuals across 60 plots located in different forest communities (Mediterranean, Eurosiberian and Mixed) coexisting within a submediterranean ecosystem in central Spain. We calculated three niche occupancy components related to Hutchinson's n-dimensional hypervolumes: the total functional volume of the community, the functional overlap between species within the community and the average functional volume per species, and then used null models to explore the relative importance of habitat filtering, limiting similarity and intraspecific variability as assembly patterns. KEY RESULTS: Both habitat filtering and niche differentiation drive the community assembly of Mediterranean communities, whereas limiting similarity and hierarchical competition shape Eurosiberian communities. Intraspecific responses were mostly explained by shifts in species niches across the functional space (changes in the position of the centroids of hypervolumes). CONCLUSIONS: Different assembly mechanisms govern the structure of Mediterranean, Eurosiberian and Mixed plant communities. Combining niche occupancy components with a null model approach at different spatial scales offers new insights into the mechanisms driving plant community assembly. Consideration of intraspecific variability is key for understanding the mechanisms governing species coexistence in species-rich ecotones.

Tackling local ecological homogeneity: Finding intraspecific trait variability in local populations of Mediterranean plants.

Local homogeneity, in ecology, is the often undisclosed assumption that variability within populations is negligible or mostly distributed evenly. In large areas, this can lead to the aggregation of different populations without regard for their unique needs and characteristics, such as drought sensitivity and functional trait distributions. Here, we discuss whether this assumption can be justified, and we hypothesize that discerning the source of variation between plasticity and adaptation could be a feasible approach to formulate an informed decision. We test this hypothesis on plants, resorting to a common garden experiment to determine the source of variation of several plant functional traits at a local scale (~60 km) of three wild species: Quercus ilex, Pistacia lentiscus, and Cistus salviifolius. Individuals of each species were sourced from three key sites chosen along a local aridity gradient. Our approach led to the rejection of the local homogeneity assumption for Q. ilex and C. salviifolius at this scale due to the adaptive divergence observed among neighboring populations. This case study provides evidence that addressing local homogeneity can highlight diverging populations in a relatively simple way. We conclude that gathering empirical evidence on intraspecific variability is a feasible approach that can provide researchers with solid bases to decide whether to adopt the local homogeneity assumption or not.

Inter- and intraspecific diversity of Salix bark phenolic profiles - A resource for the pharmaceutical industry.

Due to their content of phenolic compounds, willow bark preparations are used as an herbal remedy. The large diversity of phenolic secondary metabolites in Salix still provides a resource for the identification of bioactive compounds in particular species, including species not yet in focus from a phytopharmaceutical perspective. The present study describes the bark phenolic profile of 13 Salix species analyzed by HPLC-MS: Salix alba, Salix babylonica, Salix daphnoides, Salix fragilis, Salix hastata, Salix myrsinifolia, Salix pentandra, Salix purpurea, Salix repens (including subspecies S. repens ssp. arenaria and S. repens ssp. repens), Salix rosmarinifolia, Salix sachalinensis, Salix triandra and Salix viminalis. The analyzed profiles comprised the chemical groups of salicylates, flavonoids, procyanidins, phenolic acid derivatives, and some unclassified phenolics. Particular compounds were detected in species where they have not been previously reported. Apart from interspecific diversity, qualitative variability within species was observed as certain components were detected only in some of the analyzed genotypes. The knowledge on specific phenolic profiles of species and genotypes is the basis for the selection of suitable willow bark material with certain desired bioactive properties. Furthermore, the high inter- and intraspecific variability points out the necessity for product standardization of willow bark raw material.

Impact of sodium chloride and carbon dioxide on conidial germination and radial growth of Penicillium camemberti.

Penicillium camemberti is a domesticated species adapted to the dairy environment, which is used as adjunct cultures to ripen soft cheeses. A recent population genomics analysis on P. camemberti revealed that P. camemberti is a clonal lineage with two varieties almost identical genetically but with contrasting phenotypes in terms of growth, color, mycotoxin production and inhibition of contaminants. P. camemberti variety camemberti is found on Camembert and Brie cheeses, and P. camemberti variety caseifulvum is mainly found on other cheeses like Saint-Marcellin and Rigotte de Condrieu. This study aimed to evaluate the impact of water activity (aw) reduced by sodium chloride (NaCl) and the increase of carbon dioxide (CO2) partial pressure, on conidial germination and growth of two varieties of P. camemberti: var. Camemberti and var. Caseifulvum. Mathematical models were used to describe the responses of P. camemberti strains to both abiotic factors. The results showed that these genetically distant strains had similar responses to increase in NaCl and CO2 partial pressure. The estimated cardinal values were very close between the strains although all estimated cardinal values were significantly different (Likelihood ratio tests, pvalue = 0.05%). These results suggest that intraspecific variability could be more exacerbated during fungal growth compared with conidial germination, especially in terms of macroscopic morphology. Indeed, var. Caseifulvum seemed to be more sensitive to an increase of CO2 partial pressure, as shown by the fungal morphology, with the occurrence of irregular outgrowths, while the morphology of var. Camemberti remains circular. These data could make it possible to improve the control of fungal development as a function of salt and carbon dioxide partial pressure. These abiotic factors could serve as technological barriers to prevent spoilage and increase the shelf life of cheeses. The present data will allow more precise predictions of fungal proliferation as a function of salt and carbon dioxide partial pressure, which are significant technological hurdles in cheese production.

ERECTION OF BOTHRIOCESTUS N. GEN. (CESTODA: BOTHRIOCEPHALIDEA) AND REDESCRIPTION OF BOTHRIOCESTUS CUSPIDATUS (COOPER, 1917) (SYN. BOTHRIOCEPHALUS CUSPIDATUS) FROM WALLEYE, SANDER VITREUS, (PERCIFORMES: PERCIDAE) IN NORTH AMERICA.

Based on previous molecular phylogenetic analyses, Bothriocestus n. gen. is erected to accommodate bothriocephalid tapeworms that have an elongate scolex, a well-developed apical disc, and a narrow neck region, parasitize freshwater fishes in the Holarctic, and were previously placed in the polyphyletic genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea). Bothriocestus claviceps (Goeze, 1782) n. comb., a parasite of eels (Anguilla spp.) in the Holarctic region, is designated as the type species. Another species of the new genus, Bothriocestus cuspidatus (Cooper, 1917) (syn. Bothriocephalus cuspidatusCooper, 1917) is redescribed from type and voucher specimens, and new material from the type host, the walleye, Sander vitreus (Mitchill, 1818) (Perciformes: Percidae), in Manitoba and Ontario (where the type locality is located) (Canada) and in New York state and Wisconsin. Bothriocestus cuspidatus of S. vitreus is characterized primarily by the possession of a narrow, long strobila (total length up to 18 cm) composed of distinctly craspedote, trapezoidal proglottids, with primary, secondary, and tertiary proglottids differing in size, and by an arrow-shaped (=cuspidatus) scolex that is distinctly broader than the first proglottids, widest near the base in lateral view and gradually becoming broader toward the anterior end in dorsoventral view. A "dwarf" form of B. cuspidatus (total length of 9-27 mm) from Johnny darter, Etheostoma nigrum Rafinesque, 1820, and tessellated darter, Etheostoma olmstedi Storer, 1842 (both Percidae: Etheostominae), is also characterized morphologically in the present paper.

Sexual dimorphism in dinosaurs.

Studying fossils from a mass-mortality event reveals evidence for sexual dimorphism and, unusually, equal numbers of males and females in a herd of dinosaurs.

Variation in Seed Dormancy of Chaco Seasonally Dry Forest Species: Effects of Seed Traits and Population Environmental Conditions.

The persistence of subtropical seasonally dry forests urgently requires the implementation of ex situ conservation and restoration programs. We studied variation in seed traits and dormancy of six native species growing in seasonally dry Chaco forests of Argentina. We documented high intra- and interspecific variability in seed traits and dormancy. Fresh seeds of Geoffroea decorticans and Parasenegalia visco (Fabaceae) were water-permeable and nondormant (ND), while those of Parkinsonia praecox and Vachellia aroma (Fabaceae) were water-impermeable and had physical dormancy (PY). Seeds of Schnopsis lorentzii (Anacardiaceae) and Sarcomphalus mistol (Rhamnaceae) were water-permeable and had physiological dormancy (PD). Mechanical and chemical scarification were the most effective methods to break PY, and dry storage for 3 months was effective in breaking PD. Seeds of large-seeded species were ND or had PD, and those of small-seeded species had PY. Species inhabiting moist habitats had ND seeds, whereas those from seasonally dry habitats had seeds with PY or PD. These results suggest that seed traits and dormancy are species-specific and that intraspecific variation in seed traits is likely associated with high phenotypic plasticity of species in response to local environmental heterogeneity. These findings should be considered at the time of implementation of conservation techniques and for seed sourcing decisions for restoration.

Population variability in thermal performance of pre-spawning adult Chinook salmon.

Climate change is causing large declines in many Pacific salmon populations. In particular, warm rivers are associated with high levels of premature mortality in migrating adults. The Fraser River watershed in British Columbia, Canada, supports some of the largest Chinook salmon (Oncorhynchus tshawytscha) runs in the world. However, the Fraser River is warming at a rate that threatens these populations at critical freshwater life stages. A growing body of literature suggests salmonids are locally adapted to their thermal migratory experience, and thus, population-specific thermal performance information can aid in management decisions. We compared the thermal performance of pre-spawning adult Chinook salmon from two populations, a coastal fall-run from the Chilliwack River (125 km cooler migration) and an interior summer-run from the Shuswap River (565 km warmer migration). We acutely exposed fish to temperatures reflecting current (12°C, 18°C) and future projected temperatures (21°C, 24°C) in the Fraser River and assessed survival, aerobic capacity (resting and maximum metabolic rates, absolute aerobic scope (AAS), muscle and ventricle citrate synthase), anaerobic capacity (muscle and ventricle lactate dehydrogenase) and recovery capacity (post-exercise metabolism, blood physiology, tissue lactate). Chilliwack Chinook salmon performed worse at high temperatures, indicated by elevated mortality, reduced breadth in AAS, enhanced plasma lactate and potassium levels and elevated tissue lactate concentrations compared with Shuswap Chinook salmon. At water temperatures exceeding the upper pejus temperatures (Tpejus, defined here as 80% of maximum AAS) of Chilliwack (18.7°C) and Shuswap (20.2°C) Chinook salmon populations, physiological performance will decline and affect migration and survival to spawn. Our results reveal population differences in pre-spawning Chinook salmon performance across scales of biological organization at ecologically relevant temperatures. Given the rapid warming of rivers, we show that it is critical to consider the intra-specific variation in thermal physiology to assist in the conservation and management of Pacific salmon.