Climatic factors shaping intraspecific leaf trait variation of a neotropical tree along a rainfall gradient

Patterns of Leaf and Fruit Morphological Variation in Marginal Populations of Acer tataricum L. subsp. tataricum

Marginal populations are usually smaller and more isolated and grow in less favourable conditions than those at the distribution centre. The variability of these populations is of high importance, as it can support the adaptations needed for the conditions that they grow in. In this research, the morphological variability of eight Tatar maple (Acer tataricum L. subsp. tataricum) populations was analysed. Tatar maple is an insect-pollinated and wind-dispersed shrub/tree, whose northwestern distribution edge is in southeastern Europe. Morphometric methods were used to analyse the variability of the populations using leaf and fruit morphology. The research revealed significant differences between and within populations. Furthermore, differences in the distribution of the total variability were noted, which suggest that different evolutionarily factors affect different plant traits. Correlation analysis confirmed a weak dependency between the vegetative and generative traits. In addition, no evidence was found for the presence of isolation by environment (IBE). However, the Mantel test for isolation by distance (IBD) was significant for the leaf morphometric traits and non-significant for the fruit morphometric traits. Being the marginal leading-edge populations, they are younger and were less likely to have had time for adaptation to local environments, which would have resulted in the development of IBE. Overall, edge populations of Tatar maple were characterised by great morphological variability, which helps these populations in their response to the intensive selective pressures they face in their environment.

Divergent patterns and drivers of leaf functional traits of Robinia pseudoacacia and Pinus tabulaeformis plantations along a precipitation gradient in the Loess plateau, China

Changes in precipitation patterns in arid and semi-arid regions can reshape plant functional traits and significantly affect ecosystem functions. However, the synchronous responses of leaf economical, anatomical, photosynthetic, and biochemical traits to precipitation changes and their driving factors have rarely been investigated, which hinders our understanding of plants' ecological adaptation strategies to drought tolerance in arid areas. Therefore, the leaf traits of two typical plantations (Robinia pseudoacacia, RP and Pinus tabulaeformis, PT) along the precipitation gradient in the Loess Plateau, including economical, anatomical, photosynthetic, and biochemical traits, were investigated in this study. The results show that the leaf photosynthetic traits of RP and PT increase along the precipitation gradient, whereas leaf biochemical traits decrease. The anatomical traits of PT decrease with increasing precipitation, whereas no significant variation was observed for RP. Random Forest analysis show that LNC, LDMC, Chl, and PRO are leaf traits that significantly vary with the precipitation gradient in both plantations. Correlation analysis reveals that the traits coordination of RP is better than that of PT. The LMG model was used to determine driving factors. The results suggest that MAP explains the variation of PT leaf traits better (30.38%-36.78%), whereas SCH and SPH contribute more to the variation of RP leaf traits (20.88%-41.76%). In addition, the piecewise Structural Equation Model shows that the climate and soil physical and chemical properties directly affect the selected leaf functional traits of RP, whereas only the soil chemical properties directly affect the selected leaf functional traits of PT. The results of this study contribute to the understanding of the ecological adaptation of plants to environmental gradients and highlight that correlations among leaf traits should be considered when predicting plant adaptation strategies under future global change scenarios.

Understanding the role of zingerone on biochemical and behavioral changes in rat brain inflicted with C6 glioma cells

Malignant glioma is the deadliest form of brain cancer. Zingerone (ZO), a polyphenolic compound found in ginger, offers pharmacological properties that make it a promising agent for containing the growth of glioma cells. The present study was conducted to understand the efficacy of ZO in containing the growth of C6 glioma cells. The study also assessed the prophylactic role of ZO on rat brain glioma induced by C6 cell lines by addressing its antioxidative action on biochemical, behavioral, and histoarchitectural indices. For dose optimization, the animals were pretreated with different doses of ZO for a period of 2 weeks before the inoculation of glioma cells (1 × 105 /10 µL phosphate-buffered saline) in the caudate region of rat brain and the treatment with ZO continued for 4 more weeks post implantation. In vitro studies were done to assess the radical scavenging activity of ZO and also to determine its effects on viability of C6 glioma cells at different concentrations. Glioma-bearing rats showed significant alterations in memory; exploratory and muscular activities which were appreciably improved upon simultaneous supplementation of ZO administered at a dose of 50 mg/kg body weight and were also visible even at a higher dose. Glioma-bearing rats revealed a significant increase in reactive oxygen species, protein carbonyl contents, and lipid peroxidation, but showed a significant decrease in reduced glutathione and antioxidative enzymes in the brain tissue. Interestingly, all the biochemical indices and altered brain histoarchitecture displaying cellular atypia and hyperplasia showed appreciable improvement when supplemented with ZO at a dose of 50 mg/kg body weight.

Tropical Trees Will Need to Acclimate to Rising Temperatures-But Can They?

For tropical forests to survive anthropogenic global warming, trees will need to avoid rising temperatures through range shifts and "species migrations" or tolerate the newly emerging conditions through adaptation and/or acclimation. In this literature review, we synthesize the available knowledge to show that although many tropical tree species are shifting their distributions to higher, cooler elevations, the rates of these migrations are too slow to offset ongoing changes in temperatures, especially in lowland tropical rainforests where thermal gradients are shallow or nonexistent. We also show that the rapidity and severity of global warming make it unlikely that tropical tree species can adapt (with some possible exceptions). We argue that the best hope for tropical tree species to avoid becoming "committed to extinction" is individual-level acclimation. Although several new methods are being used to test for acclimation, we unfortunately still do not know if tropical tree species can acclimate, how acclimation abilities vary between species, or what factors may prevent or facilitate acclimation. Until all of these questions are answered, our ability to predict the fate of tropical species and tropical forests-and the many services that they provide to humanity-remains critically impaired.

Geographical variation in functional traits of leaves of Caryopteris mongholica and the role of climate

BACKGROUND

Quantifying intra-specific variation in leaf functional traits along environmental gradients is important for understanding species' responses to climate change. In this study, we assessed the degree of among and within populations variation in leaf functional traits and explored leaf response to geographic and climate change using Caryopteris mongholica as material, which has a wide range of distribution environments.

RESULTS

We selected 40 natural populations of C. mongholica, measured 8 leaf functional traits, analyzed the extent of trait variation among and within populations, and developed geographic and climatic models to explain trait variation between populations. Our results showed that the variation in leaf functional traits of C. mongholica was primarily lower within populations compared to among populations. Specifically, the leaf area (LA) exhibited higher variability both among and within populations, whereas leaf carbon content (LC) exhibited lower variation within populations but greater variation among populations. We observed a specific covariation pattern among traits and a strong linkage between morphological, economic, and mechanical traits. Increasing minimum temperature, precipitation of month, and seasonal precipitation differences all limited the growth and development of C. mongholica. However, it was observed that an increase in mean annual precipitation positively influenced the morphological development of its leaf.

CONCLUSIONS

These results demonstrate the response of intra-specific trait variation to the environment and provide valuable insights into the adaptation of intra-specific leaf functional traits under changing climatic conditions.

Phenotypic plasticity in Copaifera langsdorffii Desf. in different forest fragments in São Paulo state, Brazil

Forest fragments are susceptible to environmental shifts and this demands high phenotypic plasticity of the species growing in these areas. In this context, the objective of the present work was to study the phenotypic plasticity of copaíba (Copaifera langsdorffii Desf.) based on morphological and anatomical metrics of the leaflets of plants from six forest fragments. The leaflets of C. langsdorffii individuals of the different fragments did not show qualitative differences, nonetheless, they demonstrated quantitative plasticity. Stomatal density (p = 0.017), specific leaf area (p = 0.009), palisade parenchyma (p = 0.008) and relative water content (p = 0.002), indicated a high luminous, water and nutritional influence on the development of leaflets. Based on the dry mass of the leaflets and the thickness of the palisade parenchyma, the principal component analysis explained 57.43% of the differences found between the variables. The data presented here provides evidence of the phenotypic plasticity of C. langsdorffii which, although occurring in similar soils, showed significant quantitative differences in its morphoanatomical characters.

Cross-species transcriptomes reveal species-specific and shared molecular adaptations for plants development on iron-rich rocky outcrops soils

Background

Canga is the Brazilian term for the savanna-like vegetation harboring several endemic species on iron-rich rocky outcrops, usually considered for mining activities. Parkia platycephala Benth. and Stryphnodendron pulcherrimum (Willd.) Hochr. naturally occur in the cangas of Serra dos Carajás (eastern Amazonia, Brazil) and the surrounding forest, indicating high phenotypic plasticity. The morphological and physiological mechanisms of the plants’ establishment in the canga environment are well studied, but the molecular adaptative responses are still unknown. To understand these adaptative responses, we aimed to identify molecular mechanisms that allow the establishment of these plants in the canga environment.

Results

Plants were grown in canga and forest substrates collected in the Carajás Mineral Province. RNA was extracted from pooled leaf tissue, and RNA-seq paired-end reads were assembled into representative transcriptomes for P. platycephala and S. pulcherrimum containing 31,728 and 31,311 primary transcripts, respectively. We identified both species-specific and core molecular responses in plants grown in the canga substrate using differential expression analyses. In the species-specific analysis, we identified 1,112 and 838 differentially expressed genes for P. platycephala and S. pulcherrimum, respectively. Enrichment analyses showed that unique biological processes and metabolic pathways were affected for each species. Comparative differential expression analysis was based on shared single-copy orthologs. The overall pattern of ortholog expression was species-specific. Even so, we identified almost 300 altered genes between plants in canga and forest substrates with conserved responses in the two species. The genes were functionally associated with the response to light stimulus and the circadian rhythm pathway.

Conclusions

Plants possess species-specific adaptative responses to cope with the substrates. Our results also suggest that plants adapted to both canga and forest environments can adjust the circadian rhythm in a substrate-dependent manner. The circadian clock gene modulation might be a central mechanism regulating the plants’ development in the canga substrate in the studied legume species. The mechanism may be shared as a common mechanism to abiotic stress compensation in other native species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08449-0.

Population Variability of Almond-Leaved Willow (Salix triandra L.) Based on the Leaf Morphometry: Isolation by Distance and Environment Explain Phenotypic Diversity

Almond-leaved willow (Salix triandra L., Salicaceae) is a dioecious shrub, rarely a small tree that grows under various environmental conditions. We examined the population structure of 12 populations of almond-leaved willow using nine leaf morphological traits and specific leaf area. Populations were selected from a range of habitats, from continental to the sub-Mediterranean zone, to examine the influence of environmental conditions (climate and altitude) and geographic distance on leaf variability. Significant differences were confirmed among all populations for all traits, with significant correlations between geographic location of populations and morphological traits, and between environmental conditions and morphological traits. Large-leaved populations were found in continental and sub-Mediterranean climates, while small-leaved populations were found in higher elevations and smaller karstic rivers. In addition, populations from floodplains showed greater variability than populations from the karstic habitats, indicating a positive influence of lowland habitats and possible underlying differences in gene pool size. In conclusion, we found that environmental conditions and geographical distances in addition to genetic drift, are the main influences on the variability in almond-leaved willow, with the species showing a high level of plasticity and adaptation to local environmental conditions.

Geographic Cline and Genetic Introgression Effects on Seed Morphology Variation and Germination Fitness in Two Closely Related Pine Species in Southeast Asia

There is still limited information on how genetic introgression impacts morphological variation and population fitness in long-lived conifer species. Two closely related pine species, Pinus kesiya Royle ex Gordon and Pinus yunnanensis Franch. are widely distributed over Southeast Asia and Yunnan province of China, with a large spatial scale of asymmetric genetic introgression and hybridization, and form a hybrid lineage, P. kesiya var. langbianensis, where their ranges overlap in southeast Yunnan. We compared seed trait variation and germination performance between hybrids and parental species and characterized environmental gradients to investigate the genetic and ecological evolutionary consequences of genetic introgression. We found that seed width (SW) differed significantly among the three pines, and all the seed traits were significantly negatively correlated with latitude and associated with the mean temperatures of the driest and wettest quarters. A higher germination fitness of hybrids was detected at a low temperature, indicating that they had better adaptability to temperature stress than their parental species during the germination process. Our results suggest that environmental factors shape seed phenotypic variation in the pine species and that genetic introgression significantly affects seed germination fitness. Therefore, assisting gene flow in natural forest populations might facilitate their adaptation to climate change.

Size-dependent and environment-mediated shifts in leaf traits of a deciduous tree species in a subtropical forest

AIMS

Understanding the joint effects of plant development and environment on shifts of intraspecific leaf traits will advance the understandings of the causes of intraspecific trait variation. We address this question by focusing on a widespread species Clausena dunniana in a subtropical broad-leaved forest.

METHODS

We sampled 262 individuals of C. dunniana at two major topographic habitat types, the slope and hilltop, within the karst forests in Maolan Nature Reserve in southwestern China. We measured individual plant level leaf traits (i.e., specific leaf area (SLA), leaf area, leaf dry-matter content (LDMC), and leaf thickness) that are associated with plant resource-use strategies. We adopted a linear mixed-effects model in which the plant size (i.e., the first principal component of plant basal diameter and plant height) and environmental factors (i.e., topographic habitat, canopy height, and rock-bareness) were used as independent variables, to estimate their influences on the shifts of leaf traits.

KEY RESULTS

We found that (1) plant size and the environmental factors independently drove the intraspecific leaf trait shifts of C. dunniana, of which plant size explained less variances than environmental factors. (2) With increasing plant size, C. dunniana individuals had increasingly smaller SLA but larger sized leaves. (3) The most influential environmental factor was topographic habitat; it drove the shifts of all the four traits examined. Clausena dunniana individuals on hilltops had leaf traits representing more conservative resource-use strategies (e.g., smaller SLA, higher LDMC) than individuals on slopes. On top of that, local-scale environmental factors further modified leaf trait shifts.

CONCLUSIONS

Plant size and environment independently shaped the variations in intraspecific leaf traits of C. dunniana in the subtropical karst forest of Maolan. Compared with plant size, the environment played a more critical role in shaping intraspecific leaf trait variations, and potentially also the underlying individual-level plant resource-use strategies.

In vitro induction and identification of polyploid Neolamarckia cadamba plants by colchicine treatment

Polyploidization has played a crucial role in plant breeding and crop improvement. However, studies on the polyploidization of tropical tree species are still very scarce in this region. This paper described the in vitro induction and identification of polyploid plants of Neolamarckia cadamba by colchicine treatment. N. cadamba belongs to the Rubiaceae family is a natural tetraploid plant with 44 chromosomes (2n = 4x = 44). Nodal segments were treated with colchicine (0.1%, 0.3% and 0.5%) for 24 h and 48 h before transferring to shoot regeneration medium. Flow cytometry (FCM) and chromosome count were employed to determine the ploidy level and chromosome number of the regenerants, respectively. Of 180 colchicine-treated nodal segments, 39, 14 and 22 were tetraploids, mixoploids and octoploids, respectively. The highest percentage of polyploidization (20% octoploids; 6.7% mixoploids) was observed after treated with 0.3% colchicine for 48 h. The DNA content of tetraploid (4C) and octoploid (8C) was 2.59 ± 0.09 pg and 5.35 ± 0.24 pg, respectively. Mixoploid plants are made up of mixed tetraploid and octoploid cells. Chromosome count confirmed that tetraploid cell has 44 chromosomes and colchicine-induced octoploid cell has 88 chromosomes. Both octoploids and mixoploids grew slower than tetraploids under in vitro conditions. Morphological characterizations showed that mixoploid and octoploid leaves had thicker leaf blades, thicker midrib, bigger stomata size, lower stomata density, higher SPAD value and smaller pith layer than tetraploids. This indicates that polyploidization has changed and resulted in traits that are predicted to increase photosynthetic capacity of N. cadamba. These novel polyploid plants could be valuable resources for advanced N. cadamba breeding programs to produce improved clones for planted forest development.

Leaf trait variation during ontogeny in the endangered Brazilian rosewood tree

Knowledge of plant responses to environmental heterogeneity during ontogeny is important to elucidate the changes that occur to promote resource capture in tropical forests. We tested the hypothesis that expression changes in leaf metamer traits of Brazilian rosewood (Dalbergia nigra), from seedlings to emergent canopy trees, occur as new microclimate environments are achieved. We also tested the hypothesis that increased light heterogeneity in the understorey leads to higher plasticity in leaf traits of seedlings and saplings than in sun-exposed metamers of emergent trees subject to stressful conditions. We compared leaf metamer traits of 53 individuals including seedlings, saplings and emergent trees. We also evaluated the light heterogeneity in vertical strata and the variations in leaf traits within individuals (among metamers of the same individual). These were associated with height of the individuals. Compared to understorey plants, emergent trees presented larger metamers, with lower specific leaf area (SLA), lower investment in leaf area per total dry mass of metamer (LAR_m ), lower specific petiole length (SPL) and lower specific internode length (SIL). Higher phenotypic variation within individuals was observed in seedlings, which decreased as the trees grew taller. The results suggest the integration of ontogenetic changes in leaf traits under new microclimate conditions as the plants reach different vertical strata in the forest. Additionally, our results support the hypothesis that increased light heterogeneity in the understorey shaped higher phenotypic variation within individuals in juveniles and that stressful conditions in sun-exposed leaf metamers of emergent trees led to increased phenotypic stability.

Centre-periphery approaches based on geography, ecology and historical climate stability: what explains the variation in morphological traits of Bulnesia sarmientoi?

BACKGROUND AND AIMS

The centre-periphery hypothesis posits that higher species performance is expected in geographic and ecological centres rather than in peripheral populations. However, this is not the commonly found pattern; therefore, alternative approaches, including the historical dimension of species geographical ranges, should be explored. Morphological functional traits are fundamental determinants of species performance, commonly related to environmental stability and productivity. We tested whether or not historical processes may have shaped variations in tree and leaf traits of the Chaco tree Bulnesia sarmientoi.

METHODS

Morphological variation patterns were analysed from three centre-periphery approaches: geographical, ecological and historical. Tree (stem and canopy) and leaf (leaf size and specific leaf area) traits were measured in 24 populations across the species range. A principal component analysis was performed on morphological traits to obtain synthetic variables. Linear mixed-effects models were used to test which of the implemented centre-periphery approaches significantly explained trait spatial patterns.

KEY RESULTS

The patterns retrieved from the three centre-periphery approaches were not concordant. The historical approach revealed that trees were shorter in centre populations than in the periphery. Significant differences in leaf traits were observed between the geographical centre and the periphery, mainly due to low specific leaf area values towards the geographical centre. We did not find any pattern associated with the ecological centre-periphery approach.

CONCLUSIONS

The decoupled response between leaf and tree traits suggests that these sets of traits respond differently to processes occurring at different times. The geographical and historical approaches showed centres with extreme environments in relation to their respective peripheries, but the historical centre has also been a climatically stable area since the Last Glacial Maximum. The historical approach allowed for the recovery of historical processes underlying variation in tree traits, highlighting that centre-periphery delimitations should be based on a multi-approach framework.

Fertilization and seasonality influence on the photochemical performance of tree legumes in forest plantation for area recovery in the Amazon

N-fixing leguminous species can reach atmospheric dinitrogen gas (N₂), having an advantage under N-limited degraded environments. These N-fixers are constantly used as facilitative species. Chlorophyll a fluorescence (ChF) acknowledges how different species take up and use light energy during photosynthesis. These techniques assess stress and performance responses to photosynthesis and are used for the selection of species with potential for reforestation. Six Fabaceae species were selected for this study: three nonfixing species (Cenostigma tocantinum, Senna reticulata and Dipteryx odorata) and three N-fixing species (Clitoria fairchildiana, Inga edulis and Acacia spp.). Variations in chlorophyll fluorescence under high vs. low water and nutrient conditions were studied. Multivariate analysis was performed to detect the effects of seasonality and fertilization on dark-adapted ChF two years after the experiment was established. The correlation among ChF variables and growth, photosynthesis and foliar nutrient concentrations was evaluated. Under high water- and nutrient-availability conditions, plants exhibited an enhanced performance index on absorption basis values correlated with electron transport fluxes. Under drought and nutrient-poor conditions, most species exhibit increased energy dissipation as photoprotection. High interspecific variation was found; therefore, species-specific responses should be considered in future ChF studies. Corroborating the ability to colonize high-light environments, N-fixers showed an increased performance index correlated with electron transport and Zn and N foliar concentrations. Negative correlations were found between photosynthesis and trapped fluxes. Diameter growth was positively correlated with electron transport fluxes. Given the different responses among species, ChF is an effective technique to screen for seasonality, fertilization and species effects and should be considered for use during forest restoration. Finally, the addition of fertilization treatments may facilitate tropical forest restoration due to the importance of nutrients in physiological processes. N-fixers showed high photochemical performance and tolerance to abiotic stress in degraded areas and therefore should be included to support ecosystem biomass restoration.

Both Mature Patches and Expanding Areas of Juniperus thurifera Forests Are Vulnerable to Climate Change But for Different Reasons

Research Highlights: Water use efficiency (WUE) varied along a gradient of Juniperus thurifera (L.) forest expansion, being higher in recently colonised areas. Background and Objectives: WUE is a classic physiological process of plants that reflects the compromise between carbon assimilation and water loss and has a profound influence on their performance in water-limited environments. Forest expansion in Mediterranean regions associated with land abandonment can influence the WUE of plants due to the existence of two opposing gradients: one of favourable–unfavourable environmental conditions and another one of increased–decreased intraspecific competition, the former increasing and the latter decreasing towards the expanding front. The main objective of this study was to elucidate how the WUE of Juniperus thurifera varied along the stages of forest expansion and to provide insight on how this variation is influenced by intraspecific competition and abiotic factors. Materials and Methods: Seventeen plots at different distances from the mature forest core were selected at three sites located in the centre of the Iberian Peninsula. For 30 individuals within each plot, we measured biometric characteristics, age, tree vigour, and C/N ratio in leaves, and the leaf carbon isotope signature (δ13C (‰)) as a proxy for WUE. Around each individual, we scored the percentage cover of bare soil, stoniness, conspecifics, and other woody species. Results: WUE of J. thurifera individuals varied along the forest expansion gradient, being greater for the individuals at the expanding front than for those at the mature forest. WUE was influenced by the cover of conspecifics, tree age, and C/N ratio in leaves. This pattern reveals that less favourable environmental conditions (i.e., rocky soils and higher radiation due to lower vegetation cover) and younger trees at the expanding front are associated with increased WUE. The increased cover of conspecifics decreases irradiance at the mature forest, involving milder stress conditions than at the expanding front. Conclusions: Lower WUE in mature forests due to more favourable conditions and higher WUE due to abiotic stress at expanding fronts revealed high constraints on water economy of this tree species in these two contrasting situations. Climate change scenarios bringing increased aridity are a serious threat to Juniperus thurifera forests, affecting both mature and juvenile populations although in different ways, which deserve further research to fully unveil.

Diversity of Gall-Inducing Insects Associated With a Widely Distributed Tropical Tree Species: Testing the Environmental Stress Hypothesis

Abiotic factors can affect plant performance and cause stress, which in turn affects plant-herbivore interactions. The Environmental Stress Hypothesis (ESH) predicts that gall-inducing insect diversity will be greater on host plants that grow in stressful habitats. We tested this hypothesis, considering both historical and ecological scales, using the plant Copaifera langsdorffii Desf. (Fabaceae) as a model because it has a wide geographic distribution and is a super-host of gall-inducing insects. According to the ESH, we predicted that 1) on a historical scale, the diversity of gall-inducing insects will be higher in habitats with greater environmental stress and 2) on an ecological scale, gall-inducing insect diversity will be greater on plants that possess greater levels of foliar sclerophylly. We sampled gall-inducing insects on plants of C. langsdorffii in five sites with different levels of water and soil nutrient availability and separated from each other by a distance of up to 470 km. The composition, richness, and abundance of gall-inducing insects varied among study sites. Plants located in more stressful habitats had higher levels of foliar sclerophylly; but richness and abundance of gall-inducing insects were not affected by host plant sclerophylly. Habitat stress was a good predictor of gall-inducing insect diversity on a regional scale, thus corroborating the first prediction of the ESH. No relationship was found between plant sclerophylly and gall-inducing insect diversity within habitats. Therefore, on a local scale, we did not find support for our second prediction related to the ESH.

Geology and climate influence rhizobiome composition of the phenotypically diverse tropical tree Tabebuia heterophylla

Plant-associated microbial communities have diverse phenotypic effects on their hosts that are only beginning to be revealed. We hypothesized that morpho-physiological variations in the tropical tree Tabebuia heterophylla, observed on different geological substrates, arise in part due to microbial processes in the rhizosphere. We characterized the microbiota of the rhizosphere and soil communities associated with T. heterophylla trees in high and low altitude sites (with varying temperature and precipitation) of volcanic, karst and serpentine geologies across Puerto Rico. We sampled 6 areas across the island in three geological materials including volcanic, serpentine and karst soils. Collection was done in 2 elevations (>450m and 0-300m high), that included 3 trees for each site and 4 replicate soil samples per tree of both bulk and rhizosphere. Genomic DNA was extracted from 144 samples, and 16S rRNA V4 sequencing was performed on the Illumina MiSeq platform. Proteobacteria, Actinobacteria, and Verrucomicrobia were the most dominant phyla, and microbiomes clustered by geological substrate and elevation. Volcanic samples were enriched in Verrucomicrobia; karst was dominated by nitrogen-fixing Proteobacteria, and serpentine sites harbored the most diverse communities, with dominant Cyanobacteria. Sites with similar climates but differing geologies showed significant differences on rhizobiota diversity and composition demonstrating the importance of geology in shaping the rhizosphere microbiota, with implications for the plant's phenotype. Our study sheds light on the combined role of geology and climate in the rhizosphere microbial consortia, likely contributing to the phenotypic plasticity of the trees.

Disentangling the Environmental Factors That Shape Genetic and Phenotypic Leaf Trait Variation in the Tree Qualea grandiflora Across the Brazilian Savanna

Identifying the environmental factors that shape intraspecific genetic and phenotypic diversity of species can provide insights into the processes that generate and maintain divergence in highly diverse biomes such as the savannas of the Neotropics. Here, we sampled Qualea grandiflora, the most widely distributed tree species in the Cerrado, a large Neotropical savanna. We analyzed genetic variation with microsatellite markers in 23 populations (418 individuals) and phenotypic variation of 10 metamer traits (internode, petiole and corresponding leaf lamina) in 36 populations (744 individuals). To evaluate the role of geography, soil, climate, and wind speed in shaping the divergence of genetic and phenotypic traits among populations, we used Generalized Dissimilarity Modelling. We also used multiple regressions to further investigate the contributions of those environmental factors on leaf trait diversity. We found high genetic diversity, which was geographically structured. Geographic distance was the main factor shaping genetic divergence in Qualea grandiflora, reflecting isolation by distance. Genetic structure was more related to past climatic changes than to the current climate. We also found high metamer trait variation, which seemed largely influenced by precipitation, soil bulk density and wind speed during the period of metamer development. The high degree of metamer trait variation seems to be due to both, phenotypic plasticity and local adaptation to different environmental conditions, and may explain the success of the species in occupying all the Cerrado biome.

Variation in community structure of gall-inducing insects associated with a tropical plant supports the hypothesis of competition in stressful habitats

Environmental factors act as drivers of species coexistence or competition. Mesic environments favor the action of parasites and predators on gall communities, while the factors that determine the structure of gall communities in xeric environments remain unknown. We evaluated the structure of gall communities along an environmental gradient defined by intrinsic plant characteristics, soil fertility, and aridity, and investigated the role of competition as a structuring force of gall communities in xeric environments. We created null models to compare observed and simulated patterns of co-occurrence of galls and used the C-score index to assess community aggregation or segregation. We used the NES C-score (standardized C-score) to compare patterns of co-occurrence with parameters of environmental quality. Xeric environments had poorer and more arid soils and more sclerophyllous plants than mesic environments, which was reflected in the distribution patterns of gall communities. Values of the C-score index revealed a segregated distribution of gall morphospecies in xeric environments, but a random distribution in mesic environments. The low availability of resources for oviposition and the high density of gallers in xeric environments reinforce interspecific competition as an important structuring force for gall communities in these environments.

Soil fertility and rainfall during specific phenological phases affect seed trait variation in a widely distributed Neotropical tree, Copaifera langsdorffii

PREMISE

Knowledge of intra-specific variation in seed traits and its environmental determinants is important for predicting plant responses to environmental changes. Here, we tested the hypothesis that differences in soil fertility and rainfall during specific phenological phases drive variation in seed traits in a widely distributed tree, Copaifera langsdorffii. We also tested the hypothesis that climatic heterogeneity increases within-plant variation in seed traits.

METHODS

Inter- and intra-population and within-plant variation in seed mass, number, and seed size/seed number were evaluated for 50 individuals from five populations distributed along a rainfall gradient and occurring on varying soil types. Using multivariate approaches, we tested the effects of soil fertility characteristics and rainfall in five reproductive phenological phases on seed traits.

RESULTS

The seed traits varied greatly both among populations and within plants. Inter-population variation in seed mass was driven by total rainfall during fruit development, and variation in seed number was influenced by total rainfall during the dry season before the reproductive phase. Phosphorus levels and potential acidity of the soil also explained the variations in seed mass and seed mass/seed number, respectively. A positive association between intra-annual variation in rainfall and within-plant variation in seed mass and seed number was found.

CONCLUSION

Both rainfall during specific reproductive phases and soil conditions shape the variation in the seed mass and number of C. langsdorffii. Environment-driven seed trait variation may contribute to this species' broad niche breadth, which in turn may determine the species' persistence under future climatic conditions.