Interspecific Differences Research Articles

Strange Tunes—Acoustic Variation and Character Displacement in a Tarsier Hybrid Zone

Natural hybridization provides valuable insights into evolutionary processes, such as speciation and the forces driving or hindering it. Sulawesi tarsiers Tarsius dentatus and T. lariang hybridize within a limited area, suggesting selection against hybrids. Their species- and sex-specific duet songs might serve as a premating barrier in sympatry, especially if differences are strengthened by character displacement. Individuals of mixed origin might face disadvantages if they inherit intermediate song traits. To shed light on the processes shaping this hybrid zone, we analysed 55 duet songs from within and outside the zone. For females and males, we identified temporal and frequency-related parameters that differ between species. We inspected hybrid songs for intermediate characteristics and analysed purebred songs for character displacement in sympatry. Female hybrid songs (N = 2) were intermediate in four to five of six parameters; interpretation of male hybrid songs (N = 2) was inconclusive, because only two parameters were reliably quantifiable. There was no character displacement in female songs in sympatry (N = 11) compared with monospecific areas (N = 17). In male songs, interspecific differences in note rate were significantly larger within the hybrid zone (N = 8) compared with outside (N = 13). Intermediate song traits indicate inheritance and may disadvantage hybrids during mate choice. Character displacement in male songs is consistent with female mate choice, because females should opt for unmistakable signals to avoid costly hybridization. Our findings thus suggest that duet songs of T. lariang and T. dentatus play an important role in limiting this hybrid zone.

Interspecific Differences of Stem Diameter Variations in Response to Water Conditions for Six Tree Species in Northeast China

It is important to understand the response of stem diameter variations in dominant tree species to water conditions in Northeast China. The results will provide basic information for scientific predictions of the future development trend of temperate forests in the eastern mountainous area of northeast China. We employed a high-precision dendrometer to continuously monitor the stem radial changes of six dominant tree species in temperate forests in northeast China from 15 April to 24 October in 2021. Precipitation significantly promoted the tree stem diameter increment. The increment of stem diameter in Juglans mandshurica Maxim., Quercus mongolica Fisch. and Betula platyphylla Suk. had a significantly positive correlation with cumulative precipitation. Correlation analysis revealed that the stem radial change (SRC) of six tree species was positively correlated with precipitation (Pre) and relative humidity (RH), and negatively correlated with water vapor pressure deficit (VPD), indicating that the diameter growth of the six tree species was mainly restricted by water conditions. Under drought stress, the stem radial growth rate of the six tree species slowed down, the growth duration decreased and the tree water deficit (TWD) value increased, while there were obvious interspecific differences. Therefore, water conditions limited the stem radial growth of the six tree species, while each tree species had a different response to drought stress.

Nitrogen use strategy drives interspecific differences in plant photosynthetic CO2 acclimation.

Rising atmospheric CO2 concentration triggers an emergent phenomenon called plant photosynthetic acclimation to elevated CO2 (PAC). PAC is often characterized by a reduction in leaf photosynthetic capacity (Asat ), which varies dramatically along the continuum of plant phylogeny. However, it remains unclear whether the mechanisms responsible for PAC are also different across plant phylogeny, especially between gymnosperms and angiosperms. Here, by compiling a dataset of 73 species, we found that although leaf Asat increased significantly from gymnosperms to angiosperms, there was no phylogenetic signal in the PAC magnitude along the phylogenetic continuum. Physio-morphologically, leaf nitrogen concentration (Nm ), photosynthetic nitrogen-use efficiency (PNUE), and leaf mass per area (LMA) dominated PAC for 36, 29, and 8 species, respectively. However, there was no apparent difference in PAC mechanisms across major evolutionary clades, with 75% of gymnosperms and 92% of angiosperms regulated by the combination of Nm and PNUE. There was a trade-off between Nm and PNUE in driving PAC across species, and PNUE dominated the long-term changes and inter-specific differences in Asat under elevated CO2 . These findings indicate that nitrogen-use strategy drives the acclimation of leaf photosynthetic capacity to elevated CO2 across terrestrial plant species.

Intraspecific floral colour variation in three Pedicularis species

Flower constancy describes the phenomenon that pollinators tend to successively visit flowers of a single species during foraging, reducing reproductive interference in natural communities. The extent of flower constancy is largely determined by the floral traits of co-flowering species. Both higher inter-specific and lower intraspecific differences of floral traits should contribute to a higher level of flower constancy. However, previous studies mainly focused on interspecific difference, and the intraspecific variation (consistency) of floral traits received much less attention. We hypothesise that selection may favour lower intraspecific floral trait variation in communities composed of multiple co-flowering congeners. We investigated the floral colour variation of three focal Pedicularis species that share pollinators in 19 communities composed of either single or multiple Pedicularis species. Colour was quantified using image-based colour analysis as perceived by pollinators. We found that most of the intrapopulation floral colour variation was below the colour discrimination threshold of bumblebees, implying strongly constrained by the visual selection by pollinators. Contrary to the hypothesis, there is no significant difference in intraspecific floral colour variation between different community contexts. It may be due to the relatively large interspecific floral colour differences of most co-flowering species. The influence of community context on intraspecific variation may be reflected in floral traits other than colours.

Identification and genetic characterisatin of cathepsin L in Demodex.

Owing to difficulties in obtaining functional gene sequences, molecular pathogenic mechanisms in Demodex have been understudied. In this study, overlap extension PCR was used to obtain the sequences of cathepsin L (CatL), a pathogenicity-related gene, to provide a foundation for subsequent functional research. Demodex folliculorum and Demodex brevis mites were obtained from the face skin of Chinese individuals, and Demodex canis mites were isolated from the skin lesions of a dog. RNA was extracted and used to synthesise double-stranded cDNA. PCR amplification, cloning, sequencing, and bioinformatics analysis of CatL were performed. CatL gene sequences of 1005, 1008, and 1008bp were successfully amplified for D. brevis, D. folliculorum, and D. canis, respectively. These sequences showed 99.9 or 100% identity with templates previously obtained by RNA-seq. The Maximum Likelihood (ML) phylogenetic tree showed that D. folliculorum clustered with D. canis first, then with D. brevis, and finally with other Acariformes mite species. The three Demodex species had nine similar motifs to those of Sarcoptes scabies, Dermatophagoides pteronyssinus, and Dermatophagoides farinae, and motifs 10-13 were valuable for identification. CatL proteins of Demodex species were predicted to be approximately 38kDa, be located in lysosomes, have a signal peptide but no transmembrane region, and have two functional domains, I29 and Pept_C1. However, interspecific differences were observed in secondary and tertiary protein structures. In conclusion, we successfully obtained CatL sequences of three Demodex species by overlap extension PCR, which creates conditions for further pathogenic mechanism studies.

Unexpected morphological variability in the eggshells of the South American caimans Caiman latirostris and Caiman yacare

Eggshell morphology is a valuable indicator of the local conditions within the nests of modern crocodilians and birds. In contrast to these latter, the anatomical structure of the eggshells of most crocodilian species is practically unknown. Here, we provide the first characterization of crocodilian eggshells, using x-ray micro-CT scans. We studied eggshells of Caiman latirostris and Caiman yacare from various developmental stages that coincide with the beginning of embryonic ossification. The new 3D renderings revealed complex ornamentation, unique among crocodilians, and amphora-shaped pore canals, some of which converge in single pore openings. We also documented a high density of pore canals with a gas diffusion capacity 45 times higher than the average predicted for modern avian eggshells. The external ornamentation and the thickness of the compact layer of the eggshells (i.e. excluding ornamentation) showed ontogenetic and interspecific differences that could be related to nesting materials and nesting areas selected by each species. The shell features described here evidence a greater structural complexity than previously recognized in phylogenetically close, sympatric crocodilian species. Further comprehensive morphological analyses on other modern and fossil crocodilian eggshells using micro-CT technology will shed new light on the evolution of reproductive strategies in this intriguing archosaur clade.

Extreme low pH, not Al3+ , is a key abiotic stressor for the extremophyte Carex angustisquama (Cyperaceae) in highly acidic solfatara fields.

Volcanic acidification creates extreme soil conditions, where rhizotoxicity from extremely low pH (2-3) and high Al3+ strongly inhibit plant growth. C. angustisquama is a dominant extremophyte in highly acidic solfatara fields, where no other vascular plants can survive. Here we investigated the key abiotic stressor determining survival of this extremophyte. Soil analyses and topographic surveys were conducted to examine the effects of low pH and Al3+ , two major abiotic stressors in acidic soils, on the occurrence of C. angustisquama in solfatara fields. Hydroponic culture experiments were also performed to test its growth responses to these stressors. In field surveys, the spatial distribution of soil pH was consistent with vegetation zonation within a solfatara field. In contrast, soil exchangeable Al content was overall low due to strong eluviation. Statistical analysis also supported the significant role of soil pH in determining the distribution of C. angustisquama in a solfatara field. Furthermore, hydroponic culture experiments revealed a higher tolerance of C. angustisquama to low pH than a sister species, especially in the range pH 2-3, corresponding to the pH values of the actual habitats of C. angustisquama. Conversely, no significant interspecific difference was detected in Al3+ tolerance, indicating that both species had high Al3+ tolerance. This study suggests that low pH is a critical abiotic stressor leading to formation of the extremophyte in highly acidic solfatara fields. In contrast, C. angustisquama displayed high tolerance to Al3+ toxicity, probably acquired prior to speciation.

Resource Use among Six Commercial Fish Species from the South-Eastern Gill Net Fisheries, Korea

Dietary habits and inter-specific differences in resource use among six commercial fish species, Chelidonichthys spinosus, Cleisthenes pinetorum, Glyptocephalus stelleri, Hexagrammos otakii, Lophius litulon, and Sebastes schlegelii, collected from the southern coast of the East Sea, Korea, were analyzed using stomach content and stable isotope analyses. Teleosts were the main prey items for C. pinetorum and L. litulon, while both crabs and teleosts contributed to the diets of C. spinosus and S. schlegelii. Glyptocephalus stelleri mainly consumed polycheates and carid shrimps, and H. otakii mostly ingested crabs. The composition of prey items was significantly different in the diets of the six fish species. Further, carbon (δ13C) and nitrogen (δ15N) stable isotope values were significantly different among the six species, indicating different trophic positions. L. litulon, C. pinetorum, and S. schlegelii had narrow niches, whereas C. spinosus, G. stelleri, and H. otakii had relatively wider niches. This study demonstrated differences in patterns of food resource use among the six fish species that were categorized into two patterns of resource use according to their main prey items: diet diversity, trophic niche width, and trophic position. These results could contribute to the understanding of trophic relationships among fish species inhabiting the East Sea, Korea.

The selective drivers of allometry in sharks (Chondrichthyes: Elasmobranchii)

AbstractIn addition to the selective importance of interspecific morphological variation, ontogenetic morphological variation may reflect different selective regimes to which successive developmental stages are subjected. The typical body form of carcharhiniform sharks is considered relatively conserved, yet sharks exhibit a wide range of body sizes and shapes, representing adaptations to distinct ecological niches. Previous investigations of ontogenetic shifts in shark body form have provided evidence for both isometric and allometric changes, depending on the morphological characters and species investigated. These findings have led to suggestions of a relationship between body size and allometric growth in sharks. In this study we present evidence of ontogenetic allometric shifts in two species of carcharhiniform sharks (Sphyrna lewini and Rhizoprionodon longurio) from novel measurements. Our results are generally consistent with previous suggestions of body form conservatism across shark phylogeny, yet also suggest potential selective factors underlying observed instances of ontogenetic allometric shifts, and highlight where additional studies are required. We propose the ‘allometric niche shift’ hypothesis for interspecific differences in scaling trends, suggesting that long-distance movements and ontogenetic trophic niche shifts represent key drivers of allometry in sharks.

Blondes do it better? A comparative study on the morphometry and life-history traits of commercially important skates blonde ray Raja brachyura, thornback ray Raja clavata, and spotted ray Raja montagui, with management implications

Due to data limitation and challenges with species-specific reporting, the management of European skate fisheries currently lacks measures tailored to individual species. Given these caveats, detailed information about skate stocks at the species level is warranted. The morphometry and life-history parameters were determined for samples of 170 individuals (58 Raja brachyura, 92 R. clavata, 20 R. montagui) collected by observers in commercial fisheries, and two bottom trawl surveys (December 2020 – August 2021) in the Southern North Sea and Eastern English Channel. A combination of three morphometric measurements were considered and proven successful (3.846% misclassification, N = 78) in species discrimination for easily confusable species R. brachyura and R. montagui. Through the application of these morphometric descriptors in electronic catch monitoring via Artificial Intelligence (AI), the misidentification of easily confusable species may be reduced in future catch reporting from surveys, fisheries-dependent data, and market sampling. Additionally, the morphometric differences between species may have implications for species’ catchability, and gear modification to avoid bycatch of skates under the European Landing Obligation (LO). The length-weight relationships indicated a faster rate of increase in body mass per unit of size for R. montagui. Life-history trait parameter estimates were obtained for R. clavata and R. brachyura. Age was determined through digital processing of images from visually enhanced whole vertebral centra (0.01% crystal violet staining). Age reading precision was low (CV > 45%, PA < 60%). The von Bertalanffy and logistic growth models provided more accurate fits for the length-at-age data than the Gompertz model. Macroscopic maturity assessment revealed that male R. montagui matured at the smallest size (Lm = 57.5 cm), while female R. brachyura matured at the largest size (Lm = 87.6 cm). Maturity ogives were fitted for males (L50 = 65.4 cm) and females (L50 = 84.1) of R. clavata and females of R. brachyura (L50 = 82.7 cm), with statistically significant intersexual differences for R. clavata. The Legal Minimum Landing Size (LMLS) measures of smaller sizes may not offer adequate protection (to immature specimens) of the skate species in the present study, that mature at larger sizes. The life-history trait parameters for growth and maturity are discussed in relation to published results of earlier studies, and no major changes in the life-history parameter traits were observed in recent years. The interspecific differences in the morphometries and life-history traits of R. brachyura, R. clavata, and R. montagui highlight the need for species-specific data collection and management considerations of skate stocks in the Northeast Atlantic Region at the local and EU level.

Functional traits and climate drive interspecific differences in disturbance-induced tree mortality.

With climate change, natural disturbances such as storm or fire are reshuffled, inducing pervasive shifts in forest dynamics. To predict how it will impact forest structure and composition, it is crucial to understand how tree species differ in their sensitivity to disturbances. In this study, we investigated how functional traits and species mean climate affect their sensitivity to disturbances while controlling for tree size and stand structure. With data on 130,594 trees located on 7617 plots that were disturbed by storm, fire, snow, biotic or other disturbances from the French, Spanish, and Finnish National Forest Inventory, we modeled annual mortality probability for 40 European tree species as a function of tree size, dominance status, disturbance type, and intensity. We tested the correlation of our estimated species probability of disturbance mortality with their traits and their mean climate niches. We found that different trait combinations controlled species sensitivity to disturbances. Storm-sensitive species had a high height-dbh ratio, low wood density and high maximum growth, while fire-sensitive species had low bark thickness and high P50. Species from warmer and drier climates, where fires are more frequent, were more resistant to fire. The ranking in disturbance sensitivity between species was overall consistent across disturbance types. Productive conifer species were the most disturbance sensitive, while Mediterranean oaks were the least disturbance sensitive. Our study identified key relations between species functional traits and disturbance sensitivity, that allows more reliable predictions of how changing climate and disturbance regimes will impact future forest structure and species composition at large spatial scales.

The first articulated skull roof and braincase of Melvius chauliodous (Amiidae, Vidalamiinae) from the Upper Cretaceous Kirtland Formation, San Juan Basin, New Mexico

ABSTRACT A new, exceptionally well-preserved articulated skull roof and braincase of Melvius chauliodous, from the Kirtland Formation of New Mexico, reveals new features that provide detailed osteological information for Melvius, thus allowing for a reassessment of characters that defines the genus, its two recognized species M. chauliodous and M. thomasi, and its phylogenetic relationships within Vidalamiinae. The new features include the presence of dermopterotic rays (‘ribs’) and parietal ray bundles, previously unknown for both species of Melvius. The presence of elongated dermopterotic rays, a feature previously considered to be distinctive for the genus Calamopleurus, and tribe Calamopleurini, is now documented in Melvius, but these rays differ in their point of origination at the posteromedial corners of both dermopterotics. Bundles of short fan-shaped rays emanating from below the posterolateral corners of the parietals are also documented in both species of Melvius. Melvius was previously placed in the tribe Vidalamiini (Subfamily Vidalamiinae), but because it shares some unique features with members of the tribe Calamopleurini and the genus Calamopleurus, its placement within Vidalamiini, and the recognition of these two distinct clades (tribes) within Vidalamiinae, are not supported in our phylogenetic analysis. Previous characters distinguishing Melvius species, particularly differences in postinfraorbital ornamentation between M. chauliodous and M. thomasi, are considered dubious. However, other features may serve to determine interspecific variation or differences. For the present, we retain both species until more definitive material of M. thomasi is described.

Xylem Traumatic Resin Duct Formation in Response to Stem Fungal Inoculation in Douglas-Fir and Lodgepole Pine

Xylem traumatic resin ducts (TRDs) in Douglas-fir form in response to mechanical injury, fire, and root pathogens, but it is unknown if these form at the stem in response to bark-beetle-associated fungi. Meanwhile, TRDs are rarely documented in lodgepole pine. In the southern Rocky Mountains, TRD formation in the two species from sterile (Control) and fungal inoculation treatments (Aggressive, Weak (Douglas-fir only)) were compared; predicting the following: (1) both trees would produce TRDs in response to fungal treatments; (2) in Douglas-fir, Aggressive treatment would promote denser and larger TRDs than Weak or Control treatments; and (3) interspecifically, Douglas-fir would produce a higher density of TRDs than lodgepole pine in Aggressive treatments. Two months post-treatment, the position of TRDs indicated these were only induced on all Douglas-fir treatments. Aggressive and Weak treatments had similar responses, except a second TRD line formed in two Douglas-fir Aggressive treatments. Douglas-fir produced &gt;7× more resin ducts that were twice the size of those in lodgepole pine. Douglas-fir’s stronger induced response indicates better resistance traits against bark beetle fungal associate colonization. Understanding the characteristics of TRD produced in reaction to specific damage in Douglas-fir can improve past disturbance reconstructions and explain interspecific tree response differences conducive to bark beetle resistance.

Resource partitioning between Caucasian chamois and domestic sheep in mountain pastures of the eastern Caucasus, Dagestan, Russia

Feeding and spatial distribution of Caucasian chamois and domestic sheep were studied in the eastern Caucasus. Trophic analysis showed that the chamois diet consisted of 12 herbaceous species and 21 for sheep. Chamois selected forbs and fabaceous species, whereas sheep foraged less selectively. The trophic niche breadth (averaged) of sheep was significantly greater (9.75) than that of chamois (4.33). Trophic niche overlap reached 86% in spring and 56.6% in autumn, and the summer spatial niche breadth of chamois was lower (0.83) than that of sheep (1.46). The spatial niche overlapping of both species was low (17%). Five environmental parameters made the highest contributions to interspecific differences. Chamois habitats in spring were characterised by a lower total phytomass level and higher-calorie herbaceous group biomass (forbs, fabaceous) than in sheep-grazing areas, whereas in autumn, the high-calorie herbaceous-group biomass was higher in chamois habitats than in sheep pastures. We deduce that the chamois spatial pattern is a potential response to sheep presence; chamois moves to difficult-to-reach habitats. Therefore, ecological segregation could be potentially expected due to divergence along the spatial axis of the ecological niche.

Understanding the impact of main cell wall polysaccharides on the decomposition of ectomycorrhizal fungal necromass

AbstractThe extramatrical mycelium of ectomycorrhizal fungi (EMF) is an important source of soil carbon and nitrogen. While the importance of recalcitrant compounds in the fungal cell wall has been explored earlier, the contribution of highly abundant but labile components, like glucans, and the role of their temporal dynamics during decomposition remains unknown. For the first time, we examined how the concentration of three main fungal cell wall components (chitin, melanin, glucans) in EMF necromass are related to necromass decomposition, over a period of 6 weeks. Although the initial concentrations of the three components were not good predictors of necromass loss, we found species–specific trends of chitin and glucans loss over time. The chitin concentration during decomposition was tightly linked to the weekly necromass degradation, with trends of chitin loss being dissimilar across fungal species. Chitin concentration was positively correlated with the mass loss in the first week, but in the remaining 5 weeks, it was found to be weakly negatively correlated with mass loss. The similarity in susceptibility to the decomposition of glucans and chitin likely compensates for the impacts of interspecific differences in their initial concentration, leading to overall similar decomposition patterns. Alternatively, other, non‐measured, components (e.g., glycoproteins, N content) may contribute to explaining similar decomposition patterns. Our results indicate that ectomycorrhizal necromass decomposition processes differ from those of plant litter decomposition with, unlike in plants, differences in initial concentrations of major structural carbohydrates (e.g., glucans) being unrelated to differences in decomposition rates. These findings indicate that the decomposition of fungal material cannot be inferred from assumptions based on data provided by studies of plant decomposition.Highlights Necromass of different ectomycorrhizal species decomposes similarly Main cell wall components show different decomposition patterns The relationship between cell wall compounds and mass loss changes over time Mycorrhizal necromass decomposition differs substantially from that of plant litter.

Oysters and mussels as equivalent sentinels of microplastics and natural particles in coastal environments

Filter-feeder organisms such as oyster and mussels are exposed to particles like microplastics (MPs). Although widely used to monitor MPs contamination, little is known about their performance as sentinels, which are biological monitors accumulating contaminants without significant adverse effects. This study comparatively evaluated the quantitative and qualitative accumulation of MPs by oysters (Crassostrea brasiliana) and mussels (Perna perna) along a gradient of contamination in a highly urbanized estuarine system of Brazil. In the most contaminated site, both species presented the worst status of nutrition and health, and also one of the highest MPs levels reported for molluscs to date (up to 44.1 particles·g−1). Despite some inter-specific differences, oysters and mussels were suitable and showed an equivalent performance as sentinels, reflecting the gradient condition demonstrated for other contaminants in the region. The similarity in MPs accumulation was also observed for qualitative aspects (polymer composition, sizes, shapes and colors). Particles were mostly <1000 μm, fibrous, colorless and composed by cellulose and polymethyl methacrylate (PMMA). Thus, despite small variations, the usage of C. brasiliana and P. perna is recommended and provides reliable information for environmental levels of microplastics.

Settling and transport properties of grass carp and silver carp eggs in the water-hardened phase: Implications for resource protection and invasion control during early life period

Grass carp and silver carp eggs have no swimming ability in the water-hardened phase and need to drift for tens or even hundreds of hours before complete incubation. A full comprehensive understanding of the settling and transport properties of eggs is crucial for the resource protection and invasion control of Four Major Chinese Carps (FMCCs) during their early life stages. Artificial eggs have been used extensively in previous field and flume experiments; however, our understanding of the settling and transport properties of real eggs in the water-hardened phase remains limited. In the present study, a series of column and flume experiments were conducted in stagnant and moving water, respectively. In light of the differences in settling characteristics, caution should be exercised when applying research results obtained from artificial eggs having the closest diameter and specific gravity as real eggs. Compared with grass carp and silver carp eggs in the water-hardening phase, egg diameters in the water-hardened phase were 36% and 33% greater, respectively, and egg hydrostatic settling velocities were 31% and 40% lower, respectively. Significant interspecific differences between the two species exist in terms of egg size and hydrostatic settling velocity. Based on linear mixed effects analysis of dominant transport trajectories and regression analysis between suspending rate and flow velocity, 0.30 m/s can be considered as critical drifting velocity in uniform flow. Adaptive management schemes are discussed to promote resource protection and invasion control of FMCCs during the early life stages. The results of the present study enhance our understanding of drifting egg movement and provide insights that could facilitate the comprehensive management of FMCCs.

Functional phenotypic plasticity mediated by water stress and [CO2] explains differences in drought tolerance of two phylogenetically close conifers.

Forests are threatened globally by increased recurrence and intensity of hot droughts. Functionally close coexisting species may exhibit differences in drought vulnerability large enough to cause niche differentiation and affect forest dynamics. The effect of rising atmospheric [CO2], which could partly alleviate the negative effects of drought, may also differ between species. We analysed functional plasticity in seedlings of two taxonomically close pine species (Pinus pinaster Ait., Pinus pinea L.) under different [CO2] and water stress levels. The multidimensional functional trait variability was more influenced by water stress (preferentially xylem traits) and [CO2] (mostly leaf traits) than by differences between species. However, we observed differences between species in the strategies followed to coordinate their hydraulic and structural traits under stress. Leaf 13C discrimination decreased with water stress and increased under elevated [CO2]. Under water stress both species increased their sapwood area to leaf area ratios, tracheid density and xylem cavitation, whereas they reduced tracheid lumen area and xylem conductivity. Pinus pinea was more anisohydric than P. pinaster. Pinus pinaster produced larger conduits under well-watered conditions than P. pinea. Pinus pinea was more tolerant to water stress and more resistant to xylem cavitation under low water potentials. The higher xylem plasticity in P. pinea, particularly in tracheid lumen area, expressed a higher capacity of acclimation to water stress than P. pinaster. In contrast, P. pinaster coped with water stress comparatively more by increasing plasticity of leaf hydraulic traits. Despite the small differences observed in the functional response to water stress and drought tolerance between species, these interspecific differences agreed with ongoing substitution of P. pinaster by P. pinea in forests where both species co-occur. Increased [CO2] had little effect on the species-specific relative performance. Thus, a competitive advantage under moderate water stress of P. pinea compared with P. pinaster is expected to continue in the future.

What does critical temperature tell us about the resistance of polar lichens to freezing stress? Applicability of linear cooling method to ecophysiological studies.

Lichens from polar regions are well adapted to low temperature and considered cryoresistant. However, interspecific differences in their cryoresistance exist according to the degree of their adaptation and severity of the environment. In our study, we applied linear cooling technique in order to evaluate the interspecific differences in several lichen species. Thalli segments of Umbilicaria antarctica, Nephroma antarctica, Placopsis contortuplicata and Lasallia pustulata were exposed to the cooling from 20 to –35°C at a constant rate of 2°C min-1. Simultaneously with the cooling, chlorophyll fluorescence parameters evaluating potential (FV/FM) and effective yield of primary photochemical processes in PSII (FPSII) were measured in 30 s interval. Temperature response curves of FV/FM and FPSII formed typical S-curves that were species specific. Critical temperature (cooling point at which FPSII equals 0), was found in a narrow range of –25 to –28°C, suggesting that all experimental lichen species have a high resistance to sub-zero temperatures. The method of linear cooling used in this study has proven its applicability in ecophysiological studies since it is sensitive enough for the evaluation of species-specific differences in cryoresistance. This study describes different parameters that can be derived from the S-curves and discuss their proper use in ecophysiological and stress physiology studies.

Screening of potential chemical marker with interspecific differences in Pterocarpus wood and a spatially-resolved approach to visualize the distribution of the characteristic markers.

Profiling the spatial distributions and tissue changes of characteristic compounds with interspecific differences is critical to elucidate the complex species identification during tree species traceability, wood anti-counterfeiting verification and timber trade control. In this research, in order to visualize the spatial position of characteristic compounds in two species with similar morphology (Pterocarpus santalinus and Pterocarpus tinctorius), a high coverage MALDI-TOF-MS imaging method was used to found the mass spectra fingerprints of different wood species. 2-Mercaptobenzothiazole matrix was used to spray wood tissue section to enhance the detection effect of metabolic molecules, and the mass spectrometry imaging data were obtained. Based on this technology, the spatial location of fifteen potential chemical markers with remarkable interspecific differences in 2 Pterocarpus timber species were successfully obtained. Distinct chemical signatures obtained from this method can promote rapid identification at the wood species level. Thus, matrix-assisted laser desorption/time-of-flight/ionization mass spectrometry imaging (MALDI-TOF-MSI) provides a spatial-resolved way for traditional wood morphological classification and breaking through the limitations of traditional wood identification technology.