Edaphic specialization onto bare, rocky outcrops as a factor in the evolution of desert angiosperms.

Understanding the processes that enable organisms to shift into more arid environments as they emerge is critical for gauging resilience to climate change, yet these forces remain poorly known. In a comprehensive clade-based study, we investigate recent shifts into North American deserts in the rock daisies (tribe Perityleae), a diverse tribe of desert sunflowers (Compositae). We sample rock daisies across two separate contact zones between tropical deciduous forest and desert biomes in western North America and infer a time-calibrated phylogeny based on target capture sequence data. We infer biome shifts using Bayesian inference with paleobiome-informed models and find evidence for seven independent shifts into desert habitats since the onset of aridification in the late Miocene. The earliest shift occurred out of tropical deciduous forests and led to an extensive radiation throughout North American deserts that accounts for the majority of extant desert rock daisies. Estimates of life history and micro-habitat in the rock daisies reveal a correlation between a suffrutescent perennial life history and edaphic endemism onto rocky outcrops, an ecological specialization that evolved prior to establishment and diversification in deserts. That the insular radiation of desert rock daisies stemmed from ancestors preadapted for dry conditions as edaphic endemics in otherwise densely vegetated tropical deciduous forests in northwest Mexico underscores the crucial role of exaptation and dispersal for shifts into arid environments.

Alpine Extremophytes in Evolutionary Turmoil: Complex Diversification Patterns and Demographic Responses of a Halophilic Grass in a Central Asian Biodiversity Hotspot.

Diversification and demographic responses are key processes shaping species evolutionary history. Yet we still lack a full understanding of ecological mechanisms that shape genetic diversity at different spatial scales upon rapid environmental changes. In this study, we examined genetic differentiation in an extremophilic grass Puccinellia pamirica and factors affecting its population dynamics among the occupied hypersaline alpine wetlands on the arid Pamir Plateau in Central Asia. Using genomic data, we found evidence of fine-scale population structure and gene flow among the localities established across the high-elevation plateau as well as fingerprints of historical demographic expansion. We showed that an increase in the effective population size could coincide with the Last Glacial Period, which was followed by the species demographic decline during the Holocene. Geographic distance plays a vital role in shaping the spatial genetic structure of P. pamirica alongside with isolation-by-environment and habitat fragmentation. Our results highlight a complex history of divergence and gene flow in this species-poor alpine region during the Late Quaternary. We demonstrate that regional climate specificity and a shortage of nonclimate data largely impede predictions of future range changes of the alpine extremophile using ecological niche modeling. This study emphasizes the importance of fine-scale environmental heterogeneity for population dynamics and species distribution shifts.

Biome boundary maintained by intense belowground resource competition in world's thinnest-rooted plant community.

Recent findings point to plant root traits as potentially important for shaping the boundaries of biomes and for maintaining the plant communities within. We examined two hypotheses: 1) Thin-rooted plant strategies might be favored in biomes with low soil resources; and 2) these strategies may act, along with fire, to maintain the sharp boundary between the Fynbos and Afrotemperate Forest biomes in South Africa. These biomes differ in biodiversity, plant traits, and physiognomy, yet exist as alternative stable states on the same geological substrate and in the same climate conditions. We conducted a 4-y field experiment to examine the ability of Forest species to invade the Fynbos as a function of growth-limiting nutrients and belowground plant-plant competition. Our results support both hypotheses: First, we found marked biome differences in root traits, with Fynbos species exhibiting the thinnest roots reported from any biome worldwide. Second, our field manipulation demonstrated that intense belowground competition inhibits the ability of Forest species to invade Fynbos. Nitrogen was unexpectedly the resource that determined competitive outcome, despite the long-standing expectation that Fynbos is severely phosphorus constrained. These findings identify a trait-by-resource feedback mechanism, in which most species possess adaptive traits that modify soil resources in favor of their own survival while deterring invading species. Our findings challenge the long-held notion that biome boundaries depend primarily on external abiotic constraints and, instead, identify an internal biotic mechanism-a selective feedback among traits, plant-plant competition, and ecosystem conditions-that, along with contrasting fire regime, can act to maintain biome boundaries.

Testing the ectomycorrhizal-dominance hypothesis for ecosystem multifunctionality in a subtropical mountain forest.

Mycorrhizal associations are key mutualisms that shape the structure of forest communities and multiple ecosystem functions. However, we lack a framework for predicting the varying dominance of distinct mycorrhizal associations in an integrated proxy of multifunctionality across ecosystems. Here, we used the datasets containing diversity of mycorrhizal associations and 18 ecosystem processes related to supporting, provisioning, and regulating services to examine how the dominance of ectomycorrhiza (EcM) associations affects ecosystem multifunctionality in subtropical mountain forests in Southwest China. Meanwhile, we synthesized the prevalence of EcM-dominant effects on ecosystem functioning in forest biomes. Our results demonstrated that elevation significantly modified the distributions of EcM trees and fungal dominance, which in turn influenced multiple functions simultaneously. Multifunctionality increased with increasing proportion of EcM associations, supporting the ectomycorrhizal-dominance hypothesis. Meanwhile, we observed that the impacts of EcM dominance on individual ecosystem functions exhibited different relationships among forest biomes. Our findings highlight the importance of ectomycorrhizal dominance in regulating multifunctionality in subtropical forests. However, this ectomycorrhizal feedback in shaping ecosystem functions cannot necessarily be generalized across forests. Therefore, we argue that the predictions for ecosystem multifunctionality in response to the shifts of mycorrhizal composition could vary across space and time.

Wildfire-induced increases in photosynthesis in boreal forest ecosystems of North America.

Observations of the annual cycle of atmospheric CO2 in high northern latitudes provide evidence for an increase in terrestrial metabolism in Arctic tundra and boreal forest ecosystems. However, the mechanisms driving these changes are not yet fully understood. One proposed hypothesis is that ecological change from disturbance, such as wildfire, could increase the magnitude and change the phase of net ecosystem exchange through shifts in plant community composition. Yet, little quantitative work has evaluated this potential mechanism at a regional scale. Here we investigate how fire disturbance influences landscape-level patterns of photosynthesis across western boreal North America. We use Alaska and Canadian large fire databases to identify the perimeters of wildfires, a Landsat-derived land cover time series to characterize plant functional types (PFTs), and solar-induced fluorescence (SIF) from the Orbiting Carbon Observatory-2 (OCO-2) as a proxy for photosynthesis. We analyze these datasets to characterize post-fire changes in plant succession and photosynthetic activity using a space-for-time approach. We find that increases in herbaceous and sparse vegetation, shrub, and deciduous broadleaf forest PFTs during mid-succession yield enhancements in SIF by 8-40% during June and July for 2- to 59-year stands relative to pre-fire controls. From the analysis of post-fire land cover changes within individual ecoregions and modeling, we identify two mechanisms by which fires contribute to long-term trends in SIF. First, increases in annual burning are shifting the stand age distribution, leading to increases in the abundance of shrubs and deciduous broadleaf forests that have considerably higher SIF during early- and mid-summer. Second, fire appears to facilitate a long-term shift from evergreen conifer to broadleaf deciduous forest in the Boreal Plain ecoregion. These findings suggest that increasing fire can contribute substantially to positive trends in seasonal CO2 exchange without a close coupling to long-term increases in carbon storage.

The distribution of self-incompatibility systems in angiosperms: the relationship between mating system diversity, life span, growth habit and latitude in a changing global environment.

BACKGROUND AND AIMS: There is ample theoretical and experimental evidence that angiosperms harbouring self-incompatibility (SI) systems are likely to respond to global changes in unique ways relative to taxa with other mating systems. In this paper, we present an updated database on the prevalence of SI systems across angiosperms and examine the relationship between the presence of SI and latitude, biomes, life-history traits and management conditions to evaluate the potential vulnerability of SI taxa to climate change and habitat disturbance. METHODS: We performed literature searches to identify studies that employed controlled crosses, microscopic analyses and/or genetic data to classify taxa as having SI, self-compatibility (SC), partial self-compatibility (PSC) or self-sterility (SS). Where described, the site of the SI reaction and the presence of dimorphic versus monomorphic flowers were also recorded. We then combined this database on the distribution of mating systems with information about the life span, growth habit, management conditions and geographic distribution of taxa. Information about the geographic distribution of taxa was obtained from a manually curated version of the Global Biodiversity Information Facility database, and from vegetation surveys encompassing 9 biomes. We employed multinomial logit regression to assess the relationship between mating system and life-history traits, management condition, latitude and latitude-squared using self-compatible taxa as the baseline. Additionally, we employed LOESS regression to examine the relationship between the probability of SI and latitude. Finally, by summarizing information at the family level, we plotted the distribution of SI systems across angiosperms including information about the presence of SI or dioecy, the inferred reaction site of the SI system when known, as well as the proportion of taxa in a family for which information is available. KEY RESULTS: We obtained information about the SI status of 5686 hermaphroditic taxa, of which 55% exhibited SC, and the remaining 45% harbour SI, self-sterility (SS), or PSC. Highlights of the multinomial logit regression include that taxa with PSC have a greater odds of being short- (OR=1.3) or long- (OR=1.57) lived perennials relative to SC ones, and that SS/SI taxa (pooled) are less likely to be annuals (OR=0.64) and more likely to be long-lived perennials (OR=1.32). SS/SI taxa had a greater odds of being succulent (OR=2.4) or a tree (OR=2.05), and were less likely to be weeds (OR=0.34). Further, we find a quadratic relationship between the probability of being SI with latitude: SI taxa were more common in the tropics, a finding that was further supported by the vegetation surveys which showed fewer species with SS/SI in temperate and northern latitudes compared to mediterranean and tropical biomes. CONCLUSIONS: We conclude that in the short-term habitat fragmentation, pollinator loss and temperature increases may negatively impact plants with SI systems, particularly long-lived perennial and woody species dominant in tropical forests. In the longer term, these and other global changes are likely to select for self-compatible or partially self-compatible taxa which, due to the apparent importance of SI as a driver of plant diversification across the angiosperm tree of life, may globally influence plant species richness.

KL-Biome (Postbiotic Formulation of Lactiplantibacillus plantarum KM2) Improves Dexamethasone-Induced Muscle Atrophy in Mice.

Sarcopenia refers to an age-related decrease in muscle mass and strength. The gut-muscle axis has been proposed as a promising target to alleviate muscle atrophy. The effect of KL-Biome-a postbiotic preparation comprising heat-killed Lactiplantibacillus plantarum KM-2, its metabolites, and an excipient (soybean powder)-on muscle atrophy was evaluated using dexamethasone (DEX)-induced atrophic C2C12 myoblasts and C57BL/6J mice. KL-Biome significantly downregulated the expression of genes (Atrogin-1 and MuRF1) associated with skeletal muscle degradation but increased the anabolic phosphorylation of FoxO3a, Akt, and mTOR in C2C12 cells. Oral administration of KL-Biome (900 mg/kg) for 8 weeks significantly improved muscle mass, muscle function, and serum lactate dehydrogenase levels in DEX-treated mice. KL-Biome administration increased gut microbiome diversity and reversed DEX-mediated gut microbiota alterations. Furthermore, it significantly increased the relative abundances of the genera Subdologranulum, Alistipes, and Faecalibacterium prausnitzii, which are substantially involved in short-chain fatty acid production. These findings suggest that KL-Biome exerts beneficial effects on muscle atrophy by regulating gut microbiota.

Garcinia macrophylla: a Promising Underutilized Source of Bioactive Compounds in the Amazonia - A Review.

Native species from the Amazonia are still unknown or underutilized and few information about their chemical and biological properties are available in the literature. Among the underutilized plant species in the Amazonia, Garcinia macrophylla can be seen as a promising source of bioactive compounds with relevant biological properties. The stem bark and leaves were the main investigated plant parts, mainly concerning the antioxidant, antibacterial, cytotoxicity and antidiabetic properties. However, the bioactive compounds and biological properties of the edible fruits were not yet reported. Systematic investigations covering the Amazonia biome, concerning plants and vegetables as strategic resources are of paramount importance for the sustainable development of the forest. Therefore, this review gathered the available information in the literature concerning general aspects, chemical profile and biological properties of G. macrophylla, for the first time, which highlighted that systematic and robust in vitro and in vivo research, are still needed to elucidate the phytochemical profiles and associated relevant biological properties.

Meta-analysis shows forest soil CO2 effluxes are dependent on the disturbance regime and biome type.

Forest soil CO2 efflux (FCO2 ) is a crucial process in global carbon cycling; however, how FCO2 responds to disturbance regimes in different forest biomes is poorly understood. We quantified the effects of disturbance regimes on FCO2 across boreal, temperate, tropical and Mediterranean forests based on 1240 observations from 380 studies. Globally, climatic perturbations such as elevated CO2 concentration, warming and increased precipitation increase FCO2 by 13% to 25%. FCO2 is increased by forest conversion to grassland and elevated carbon input by forest management practices but reduced by decreased carbon input, fire and acid rain. Disturbance also changes soil temperature and water content, which in turn affect the direction and magnitude of disturbance influences on FCO2 . FCO2 is disturbance- and biome-type dependent and such effects should be incorporated into earth system models to improve the projection of the feedback between the terrestrial C cycle and climate change.

Herbaceous vegetation responses to experimental fire in savannas and forests depend on biome and climate.

Fire-vegetation feedbacks potentially maintain global savanna and forest distributions. Accordingly, vegetation in savanna and forest ecosystems should have differential responses to fire, but fire response data for herbaceous vegetation have yet to be synthesized across biomes. Here, we examined herbaceous vegetation responses to experimental fire at 30 sites spanning four continents. Across a variety of metrics, herbaceous vegetation increased in abundance where fire was applied, with larger responses to fire in wetter and in cooler and/or less seasonal systems. Compared to forests, savannas were associated with a 4.8 (±0.4) times larger difference in herbaceous vegetation abundance for burned versus unburned plots. In particular, grass cover decreased with fire exclusion in savannas, largely via decreases in C4 grass cover, whereas changes in fire frequency had a relatively weak effect on grass cover in forests. These differential responses underscore the importance of fire for maintaining the vegetation structure of savannas and forests.

The evolution of extant South American tropical biomes.

This review explores the evolution of extant South American tropical biomes, focusing on when and why they developed. Tropical vegetation experienced a radical transformation from being dominated by non-angiosperms at the onset of the Cretaceous to full angiosperm dominance nowadays. Cretaceous tropical biomes do not have extant equivalents; lowland forests, dominated mainly by gymnosperms and ferns, lacked a closed canopy. This condition was radically transformed following the massive extinction event at the Cretaceous-Paleogene boundary. The extant lowland tropical rainforests first developed at the onset of the Cenozoic with a multistratified forest, an angiosperm-dominated closed canopy, and the dominance of the main families of the tropics including legumes. Cenozoic rainforest diversity has increased during global warming and decreased during global cooling. Tropical dry forests emerged at least by the late Eocene, whereas other Neotropical biomes including tropical savannas, montane forests, páramo/puna, and xerophytic forest are much younger, greatly expanding during the late Neogene, probably at the onset of the Quaternary, at the expense of the rainforest.

Functional trade-offs are driven by coordinated changes among cell types in the wood of angiosperm trees from different climates.

Wood performs several functions to ensure tree survival and carbon allocation to a finite stem volume leads to trade-offs among cell types. It is not known to what extent these trade-offs modify functional trade-offs and if they are consistent across climates and evolutionary lineages. Twelve wood traits were measured in stems and coarse roots across 60 adult angiosperm tree species from temperate, Mediterranean and tropical climates. Regardless of climate, clear trade-offs occurred among cellular fractions, but did not translate into specific functional trade-offs. Wood density was negatively related to hydraulic conductivity (Kth ) in stems and roots, but was not linked to nonstructural carbohydrates (NSC), implying a functional trade-off between mechanical integrity and transport but not with storage. NSC storage capacity was positively associated with Kth in stems and negatively in roots, reflecting a potential role for NSC in the maintenance of hydraulic integrity in stems but not in roots. Results of phylogenetic analyses suggest that evolutionary histories cannot explain covariations among traits. Trade-offs occur among cellular fractions, without necessarily modifying trade-offs in function. However, functional trade-offs are driven by coordinated changes among xylem cell types depending on the dominant role of each cell type in stems and roots.

Jack pine of all trades: Deciphering intraspecific variability of a key adaptive trait at the rear edge of a widespread fire-embracing North American conifer.

PREMISE: Understanding mechanisms fostering long-term persistence of marginal populations should provide key insights about species resilience facing climate change. Cone serotiny is a key adaptive trait in Pinus banksiana (jack pine), which shows phenotypic variation according to the fire regime. Compared to range-core populations within the fire-prone boreal forest, low and variable serotiny in rear-edge populations suggest local adaptation to uncommon and unpredictable wildfire regime. We assessed environmental/physiological factors that might modulate intraspecific variation in cone serotiny. METHODS: We experimentally subjected closed cones to incrementing temperatures, then tested seed germination to determine whether and how various ecological factors (cone age, branch height, tree size, tree age) are related to cone dehiscence and seed viability in jack pines from rear-edge and range-core populations in eastern Canada. RESULTS: Cones from rear-edge populations dehisce at a lower opening temperature, which increases with cone age. Cones from range-core stands open at a more constant, yet higher temperature. Cones from rear-edge stands take between 13 and 27 years to reach the level of serotiny achieved at the range core. At the rear edge, seed viability is steady (51%), whereas it decreases from 70% to 30% in 20 years at the range core. CONCLUSIONS: We inferred the mechanisms of a bet-hedging strategy in rear-edge populations, which ensures steady recruitment during fire-free intervals and successful postfire regeneration. This capacity to cope with infrequent and unpredictable fire regime should increase the resilience of jack pine populations as global changes alter fire dynamics of the boreal forest.

High spatial resolution solar-induced chlorophyll fluorescence and its relation to rainfall precipitation across Brazilian ecosystems.

The detection of Solar-Induced chlorophyll Fluorescence (SIF) by remote sensing has opened new perspectives on ecosystem studies and other related aspects such as photosynthesis. In general, fluorescence high-resolution studies were limited to proximal sensors, but new approaches were developed to improve SIF resolution by combining OCO-2 with MODIS orbital observations, improving its resolution from 0.5° to 0.05 on a global scale. Using a high-resolution dataset and rainfall data some SIF characteristics of the satellite were studied based across 06 contrasting ecosystems in Brazil: Amazonia, Caatinga, Cerrado, Atlantic Forest, Pampa, and Pantanal, from years 2015-2018. SIF spatial variability in each biome presented significant spatial variability structures with high R2 values (>0.6, Gaussian models) in all studied years. The rainfall maps were positively and similar related to SIF spatial distribution and were able to explain more than 40% of SIF's spatial variability. The Amazon biome presented the higher SIF values (>0.4 W m-2 sr-1 µm-1) and also the higher annual rainfall precipitation (around 2000 mm), while Caatinga had the lowest SIF values and precipitations (<0.1 W m-2 sr-1 µm-1, precipitation around 500 mm). The linear relationship of SIF to rainfall across biomes was mostly significant (except in Pantanal) and presented contrasting sensitivities as in Caatinga SIF was mostly affected while in the Amazon, SIF was lesser affected by precipitation events. We believe that the features presented here indicate that SIF could be highly affected by rainfall precipitation changes in some Brazilian biomes. Combining rainfall with SIF allowed us to detect the differences and similarities across Brazil's biomes improving our understanding on how these ecosystems could be affected by climate change and severe weather conditions.

Bio-Prospecting of Crude Leaf Extracts from Thirteen Plants of Brazilian Cerrado Biome on Human Glioma Cell Lines.

(1) Background: Malignant gliomas are aggressive tumors characterized by fast cellular growth and highly invasive properties. Despite all biological and clinical advances in therapy, the standard treatment remains essentially palliative. Therefore, searching for alternative therapies that minimize adverse symptoms and improve glioblastoma patients' outcomes is imperative. Natural products represent an essential source in the discovery of such new drugs. Plants from the cerrado biome have been receiving increased attention due to the presence of secondary metabolites with significant therapeutic potential. (2) Aim: This study provides data on the cytotoxic potential of 13 leaf extracts obtained from plants of 5 families (Anacardiaceae, Annonaceae, Fabaceae, Melastomataceae e Siparunaceae) found in the Brazilian cerrado biome on a panel of 5 glioma cell lines and one normal astrocyte. (3) Methods: The effect of crude extracts on cell viability was evaluated by MTS assay. Mass spectrometry (ESI FT-ICR MS) was performed to identify the secondary metabolites classes presented in the crude extracts and partitions. (4) Results: Our results revealed the cytotoxic potential of Melastomataceae species Miconia cuspidata, Miconia albicans, and Miconia chamissois. Additionally, comparing the four partitions obtained from M. chamissois crude extract indicates that the chloroform partition had the greatest cytotoxic activity against the glioma cell lines. The partitions also showed a mean IC50 close to chemotherapy, temozolomide; nevertheless, lower toxicity against normal astrocytes. Analysis of secondary metabolites classes presented in these crude extracts and partitions indicates the presence of phenolic compounds. (5) Conclusions: These findings highlight M. chamissois chloroform partition as a promising component and may guide the search for the development of additional new anticancer therapies.

Deforestation impacts on dengue incidence in the Brazilian Amazon.

The objective of the study is to perform the spatial analysis of the conditioning factors for the increase in the incidence rate of dengue cases in municipalities located in the Amazon biome, in the period from 2016 to 2021. Three statistical approaches were applied: Moran's index, ordinary least squares regression, and geographically weighted regression. The results revealed that the incidence rates of dengue cases cluster in two areas, both located in the south of the Amazon biome, which is associated with the Arc of Deforestation. The variable deforestation influences the increase in dengue incidence rates revealed by the OLS and GWR model. The adjusted R2 of the GWR model was 0.70, that is, the model explains about 70% of the total case variation of dengue incidence rates in the Amazon biome. The results of the study evidence the need for public policies aimed at the prevention and combat of deforestation in the Amazon region.

High prevalence of pathogenic Eimeria spp. and the main risk factors associated with infection in goats from a semiarid region of Northeastern Brazil.

This study aimed to analyze the epidemiology of infections caused by Eimeria spp. in goats bred in an extensive production system in Northeast Brazil. To this end, an epidemiological survey was performed, wherein 350 fecal samples were collected from goats ranging from 3 months to 8 years old across 30 farms. The number of oocysts per gram of feces (OPG) was counted using the Mini-FLOTAC method. Species were identified based on their morphological and morphometric characteristics. Frequencies between animal categories were assessed using the chi-square test and known risk factors after multivariate analysis. Eimeria oocysts were found in 99.4% (346/348) of samples and 100% (30/30) of the farms. The OPG was influenced by the age of the animals; therefore, young goats (up to 6 months old) eliminated more oocysts (2302.6 + 5454.8) than adult goats (881.7 + 1551.5). Three pathogenic species were identified, with two demonstrating a high prevalence: Eimeria arloingi (88.83%) and Eimeria christenseni (44.7%), in addition to Eimeria caprina (3.72%). In the study, the habit of ground feeding and the use of cisterns as water sources were identified as risk factors, with odds ratios of 4.04 and 9.82, respectively. However, cleaning facilities at shorter intervals was a protective factor (OR = 0.19). We concluded that there was a high prevalence of Eimeria infection in goats bred in extensive production systems, even those in semiarid regions. This high prevalence can be attributed to the congregation of animals in shaded areas and the substantial accumulation of fecal matter at night.

Net plant interactions are highly variable and weakly dependent on climate at the global scale.

Although plant-plant interactions (i.e. competition and facilitation) have long been recognised as key drivers of plant community composition and dynamics, their global patterns and relationships with climate have remained unclear. Here, we assembled a global database of 10,502 pairs of empirical data from the literature to address the patterns of and climatic effects on the net outcome of plant interactions in natural communities. We found that plant interactions varied among plant performance indicators, interaction types and biomes, yet competition occurred more frequently than facilitation in plant communities worldwide. Unexpectedly, plant interactions showed weak latitudinal pattern and were weakly related to climate. Our study provides a global comprehensive overview of plant interactions, highlighting competition as a fundamental mechanism structuring plant communities worldwide. We suggest that further investigations should focus more on local factors (e.g. microclimate, soil and disturbance) than on macroclimate to identify key environmental determinants of interactions in plant communities.

Temperature responses of photosynthesis and respiration in evergreen trees from boreal to tropical latitudes.

Evergreen species are widespread across the globe, representing two major plant functional forms in terrestrial models. We reviewed and analysed the responses of photosynthesis and respiration to warming in 101 evergreen species from boreal to tropical biomes. Summertime temperatures affected both latitudinal gas exchange rates and the degree of responsiveness to experimental warming. The decrease in net photosynthesis at 25°C (Anet25 ) was larger with warming in tropical climates than cooler ones. Respiration at 25°C (R25 ) was reduced by 14% in response to warming across species and biomes. Gymnosperms were more sensitive to greater amounts of warming than broadleaved evergreens, with Anet25 and R25 reduced c. 30-40% with > 10°C warming. While standardised rates of carboxylation (Vcmax25 ) and electron transport (Jmax25 ) adjusted to warming, the magnitude of this adjustment was not related to warming amount (range 0.6-16°C). The temperature optimum of photosynthesis (ToptA ) increased on average 0.34°C per °C warming. The combination of more constrained acclimation of photosynthesis and increasing respiration rates with warming could possibly result in a reduced carbon sink in future warmer climates. The predictable patterns of thermal acclimation across biomes provide a strong basis to improve modelling predictions of the future terrestrial carbon sink with warming.

Limited dispersal and local adaptation promote allopatric speciation in a biodiversity hotspot.

Recently diverged or diverging populations can offer unobstructed insights into early barriers to gene flow during the initial stages of speciation. The current study utilised a novel insect system (order Mantophasmatodea) to shed light on the early drivers of speciation. The members of this group have limited dispersal abilities, small allopatric distributions and strong habitat associations in the Cape Floristic Region biodiversity hotspot in South Africa. Sister taxa from the diverse family Austrophasmatidae were chosen as focal species (Karoophasma biedouwense, K. botterkloofense). Population genetics and Generalized Dissimilarity Modelling (GDM) were used to characterise spatial patterns of genetic variation and evaluate the contribution of environmental factors to population divergence and speciation. Extensive sampling confirmed the suspected allopatry of these taxa. However, hybrids were identified in a narrow region occurring between the species' distributions. Strong population structure was found over short geographic distances; particularly in K. biedouwense in which geographic distance accounted for 32% of genetic variation over a scale of 50 km (r = .56, p < .001). GDM explained 42%-78% of the deviance in observed genetic dissimilarities. Geographic distance was consistently indicated to be important for between species and within population differentiation, suggesting that limited dispersal ability may be an important neutral driver of divergence. Temperature, altitude, precipitation and vegetation were also indicated as important factors, suggesting the possible role of adaptation to local environmental conditions for species divergence. The discovery of the hybrid-zone, and the multiple allopatric species pairs in Austrophasmatidae support the idea that this could be a promising group to further our understanding of speciation modes.