Drivers Of Variation Research Articles

The Andes are a driver of physiological diversity in Anolis lizards

Abstract The Andes, with its diverse topography and climate, is a renowned cradle for adaptive radiation, particularly for vertebrate ectotherms like lizards. Yet, the role of temperature in promoting physiological specialization in the Andes remains unclear. Aseasonality in the tropics should favor physiological specialization across elevation in lizards, but empirical data are limited and equivocal. Determining how thermal tolerances are geographically and phylogenetically structured, therefore, is a priority, particularly as environments continue to rapidly change. However, there's a gap in our knowledge of thermal limits of species from the Andes, one of the planet’s most biodiverse regions. Anoles, a diverse lizard group found across thousands of meters of elevation in the Andes, can offer insights into evolutionary adaptations to temperature. This study focused on 14 anole species from two clades (Dactyloa and Draconura) that independently diversified along elevational gradients in the Andes. We measured critical thermal limits (CTmin and CTmax) and found patterns of thermal tolerance specialization across elevation, both among and within species. Patterns of thermal specialization are similar among anole clades, indicating parallel responses to similar environmental pressures. Specifically, high-elevation anoles are more cold tolerant and less heat tolerant than their low elevation counterparts, rendering thermal tolerance breadths stable across elevation (thermal specialization). Evolutionary rates of physiological traits were similar, reflecting parallel specialization in heat and cold tolerance across elevation. The adaptive radiation of anole lizards reflects physiological specialization across elevation, and the endemism such specialization favors likely catalyzed their remarkable diversity in the tropical Andes.

Exploring the driving factors of bird diversity in mangrove natural protected areas in Guangdong Province, China

IntroductionUnder the impacts of high intensity human activities, mangrove natural protected areas are pivotal strategies for biodiversity conservation and play a significant role in preserving bird diversity. Mangrove natural protected areas in Guangdong Province, China, lie along the migratory path of the East Asian-Australasian Flyway, serving as breeding, feeding, and resting grounds for birds. Variations in bird responses to environmental factors are significant.MethodsTo comprehensively understand these variances, redundancy analysis was employed, focusing on bird diversity surveys conducted from March 2022 to February 2023 in natural protected areas of Guangdong to examine how driving factors such as mangrove habitat landscape, community structure, water quality, and soil sedimentation affected the diversity of avian species.ResultsThe findings were as follows: (1) A total of 193 bird species spanning 17 orders and 53 families were documented, including 74 songbirds, 60 wading birds, 27 swimming birds, 17 climbing birds, 10 raptors, and 5 terrestrial birds. (2) Regarding the impact of simple effects on all bird species, aquaculture pond area, mangrove extent, and mudflat area emerged as significant factors driving bird diversity, with explanatory rates of 31.0%, 28.9%, and 20.3%, respectively. Notably, the aquaculture pond area was the main driver of bird diversity, with an explanatory rate of 31.0%. (3) Mangrove extent has emerged as a pivotal factor shaping the songbird diversity, climbing birds, raptors, and terrestrial birds, whereas the aquaculture pond area was pivotal for wading birds, swimming birds, and others.DiscussionTo enhance mangrove bird diversity protection, management agencies overseeing natural mangrove protected areas should adopt science-based approaches when managing mangrove, mudflats, and aquaculture pond areas in mangrove forest protection and restoration plans. This would prevent extensive mangrove planting, which encroaches on non-mangrove habitats. Additionally, the scientific management of aquaculture ponds should accommodate diverse bird habitats through measures, such as water level adjustments.

Landscape-scale drivers of spatial dynamics and genetic diversity in an emerging wildlife pathogen

Aquatic pathogens often cannot tolerate drying, and thus their spread, and diversity across a landscape may depend on interactions between hydrological conditions and the movement of infected hosts. The aquatic fungus Batrachochytrium dendrobatidis (Bd) is a nearly ubiquitous pathogen of amphibians and particular lineages have been associated with host declines. By coupling amphibian surveys with molecular pathogen detection and genotyping techniques, we characterized the spatial dynamics and genetic diversity of Bd on a landscape containing both permanent and ephemeral ponds. In doing so, we aimed to clarify how pathogen loads and prevalences vary across seasons and among habitat types, and which host species move the pathogen from place to place. At the start of spring breeding, Bd prevalence was lower on amphibians sampled from ephemeral ponds. For the remainder of the amphibian active season, prevalence was similar across both ephemeral and permanent ponds, with variation in prevalence being well-explained by a hump-shaped relationship with host body temperature. The first amphibians to arrive at these ephemeral ponds infected were species that breed in ephemeral ponds and likely emerged infected from terrestrial hibernacula. However, species from permanent ponds, most of which hibernate aquatically, later visited the ephemeral ponds and these animals had a greater prevalence and load of Bd, suggesting that migrants among ponds and pond types also move Bd across the landscape. The Bd we sampled was genetically diverse within ponds but showed little genetic structure among ponds, host species, or seasons. Taken together, our findings suggest that Bd can be diverse even at small scales and moves readily across a landscape with help from a wide variety of hosts.

Mapping elevational patterns of functional diversity of canopy species in an alpine forest using drone multispectral and LiDAR data

Understanding the patterns and drivers of plant functional diversity is crucial for assessing the functioning and resilience of terrestrial ecosystems to global climate change. Despite the well-documented variability in plant species richness with elevation, the elevational patterns and underlying mechanisms of functional diversity remain poorly understood. This study employed drone equipped with multispectral and light detection and ranging (LiDAR) sensors to investigate the elevational gradients (3208 m to 3984 m) of physiological and morphological functional diversity of canopy tree species in six 1-hectare plots in Baima Snow Mountain, Yunnan, China. Results demonstrated that drone-based multispectral and LiDAR data enabled high-resolution mapping of physiological and morphological functional diversity in forest canopies over large areas. Importantly, functional diversity declined with increasing elevation, with a more pronounced pattern observed for physiological traits compared to morphological traits. Variance partitioning analysis revealed that functional richness was primarily driven by climatic and edaphic factors, particularly temperature, while plant factors played a subordinate role, interacting with climate and soil. Our findings highlight the potential of drone for rapid, large-scale monitoring and mapping of canopy species functional diversity in forests. Moreover, the influence of climate and soil factors on functional diversity suggests that future global warming may enhance functional diversity in alpine forest ecosystems, with implications for ecosystem functioning and services.

Potential drivers of plant diversity and composition in high-altitude alpine regions of Himalaya

Potential drivers of plant diversity and composition in high-altitude alpine regions of Himalaya

Navigating the Zooplankton Realm: Oceans of Diversity Beneath the Sea Surface

This review provides a comprehensive summary of the current knowledge on marine zooplankton diversity and distribution, highlighting key advancements and future directions in the field. While the approach used in this review is necessarily broad, focusing on overarching trends and drivers of zooplankton diversity, it emphasizes recent methodological innovations. The review begins with an introduction to zooplankton, tracing the historical development of their research. It then explores the critical roles zooplankton play in ocean ecosystems, climate change, and the global economy. Next, the review examines the environmental and anthropogenic factors influencing marine zooplankton. Finally, it presents a comparison between marine and freshwater zooplankton and concludes with a discussion of the challenges facing current zooplankton diversity research and the presentation of possible directions and implementation strategies for advancing the understanding of zooplankton biodiversity and ecology.

Divergent Drivers of Declining Urban Vegetation Productivity and Transpiration During Heatwaves

AbstractHeatwave events, characterized by high vapor pressure deficit (VPD) and low soil moisture (SM), considerably disrupt the regional carbon and water cycle. However, research pertaining to the impact of heatwaves on vegetation productivity (VPu) and vegetation transpiration (VTu), along with their underlying drivers, particularly in urban areas, remains limited. This study investigates the response of VPu and VTu to heatwave events across 895 global cities from 1990 to 2022. The analysis reveals a notable upward trend in the average heatwave frequency, intensity, and duration across the global cities. Heatwave events demonstrate a detrimental impact on VPu and VTu, resulting in an average decrease of 28% and 26%, respectively, during heatwave occurrences. The attribution analysis reveals divergent driving factors for the decline in VPu and VTu during heatwaves. The decrease in VPu is primarily influenced by SM, contributing 60% to the downward trend of VPu during heatwaves. Notably, VPu displays a sharp downward trend when SM falls below 0.38 m3/m3. In contrast, the primary driver of VTu decline is VPD, contributing more than 66% to the downward trend of VTu during heatwave events. VTu exhibits a significant downward trend when VPD exceeds 1.35 kPa. The results of this study show the important effects of increasingly frequent heatwaves on vegetation transpiration and productivity, and that can be used as quantitative factor to be evaluated when investigating policy measures for the resilience of urban areas.

Diversity and prevalence of Leucocytozoon in black flies (Diptera: Simuliidae) of Thailand.

Leucocytozoonosis, a parasitic disease of birds, is caused by haemosporidian protozoan parasites of the genus Leucocytozoon, which infect diverse avian species, including poultry. These parasites are transmitted by several black fly species, but knowledge of the factors determining the diversity and prevalence in these vectors, which is crucial for fully understanding disease epidemiology, is largely unexplored. In this study, we investigated factors associated with the prevalence and diversity of Leucocytozoon species in black flies from Thailand. Adults of two black fly taxa (Simulium asakoae Takaoka and Davies complex and S. khelangense Takaoka, Srisuka and Saeung) were collected using sweep nets at nine locations in northern and northeastern regions of Thailand. Specimens were identified morphologically and the results corroborated by DNA barcoding. Molecular methods using specific primers for amplification of the mitochondrial cytochrome b (cyt b) gene of Leucocytozoon were used to detect the parasite in black flies. Species and lineages of Leucocytozoon were determined using the MalAvi database of malaria parasites and related haemosporidians in avian hosts. Regression analysis was used to examine relationships between Leucocytozoon diversity and prevalence, black fly abundance and habitat characteristics. A total of 11,718 adult black flies were collected, of which 4367 were members of the S. asakoae complex and 7351 were S. khelangense. For molecular detection of Leucocytozoon, we randomly selected 300 individual female black flies of the S. asakoae complex and 850 females of S. khelangense pooled into groups of five individuals (= 170 pools). A total of 34 of the 300 specimens of the S. asakoae complex and 118 of the 170 pools of S. khelangense were positive for Leucocytozoon. Fifty-four lineages (haplotypes) were identified, all of which belonged to those reported in domestic chickens, Gallus gallus, with one exception that was identified in S. khelangense and found to be closely related to the Leucocytozoon lineages reported in owls; this is the first record of the latter lineage in Asian black flies. Among these haplotypes, nine and 45 were exclusively found in the S. asakoae complex and S. khelangense, respectively. No lineage was shared between these black fly taxa. Analysis of similarity (ANOSIM) revealed significant Leucocytozoon lineage composition between the two black flies. Phylogenetic analysis found that Leucocytozoon lineages in the S. asakoae complex and S. khelangense are largely isolated, agreeing with the ANOSIM result. The overall prevalence of Leucocytozoon in the S. asakoae complex was 11.3% and ranged from 9% to 13% in each collection. Leucocytozoon prevalence in S. khelangense was 21%, varying from 13% to 37% in each collection. The Shannon H' index indicated greater Leucocytozoon diversity in S. khelangense (H' = 3.044) than in the S. asakoae complex (H' = 1.920). Regression analysis revealed that Leucocytozoon diversity was positively related to black fly abundance and negatively related to maximum air temperature. The results of this study show that the prevalence and diversity of Leucocytozoon lineages in the S. asakoae complex and S. khelangense from Thailand were associated with the abundance of these black flies and with air temperature. The Leucocytozoon lineages identified also showed some degree of black fly taxon specificity, possibly related to different abundance peaks of these vectors. The environmental conditions that favor the development of black flies are possibly a driver of Leucocytozoon prevalence, diversity and vector-parasite co-evolution.

START domains generate paralog-specific regulons from a single network architecture

Functional divergence of transcription factors (TFs) has driven cellular and organismal complexity throughout evolution, but its mechanistic drivers remain poorly understood. Here we test for new mechanisms using CORONA (CNA) and PHABULOSA (PHB), two functionally diverged paralogs in the CLASS III HOMEODOMAIN LEUCINE ZIPPER (HD-ZIPIII) family of TFs. We show that virtually all genes bound by PHB ( ~ 99%) are also bound by CNA, ruling out occupation of distinct sets of genes as a mechanism of functional divergence. Further, genes bound and regulated by both paralogs are almost always regulated in the same direction, ruling out opposite regulation of shared targets as a mechanistic driver. Functional divergence of CNA and PHB instead results from differential usage of shared binding sites, with hundreds of uniquely regulated genes emerging from a commonly bound genetic network. Regulation of a given gene by CNA or PHB is thus a function of whether a bound site is considered ‘responsive’ versus ‘non-responsive’ by each paralog. Discrimination between responsive and non-responsive sites is controlled, at least in part, by their lipid binding START domain. This suggests a model in which HD-ZIPIII TFs use information integrated by their START domain to generate paralog-specific transcriptional outcomes from a shared network architecture. Taken together, our study identifies a mechanism of HD-ZIPIII TF paralog divergence and proposes the ubiquitously distributed START evolutionary module as a driver of functional divergence.

Oceanic islands act as drivers for the genetic diversity of marine species: Cardita calyculata (Linnaeus, 1758) in the NE Atlantic as a case-study

Geographic distribution, as well as evolutionary and biogeographic processes and patterns of marine invertebrate benthic species are strongly shaped by dispersal ability during the life cycle. Remote oceanic islands lie at the brink of complex biotic and abiotic interactions which have significantly influenced the biodiversity patterns we see today. The interaction between geological environmental change and taxon-specific dispersal modes can influence species evolutionary patterns, eventually delimiting species-specific biogeographic regions. In this study, we compare the population genetic patterns of the marine bivalve Cardita calyculata in the northeast Atlantic, discussing the role of Macaronesian islands during past climatic cycles. The genetic structure and diversity patterns were outlined based on SSR-GBAS loci of 165 individuals and on the mitochondrial COI marker of 22 individuals from the Canary Islands, Madeira, Azores and the Mediterranean. The highly structured genetic pattern found among regions and within archipelagos suggests the central role of oceanic islands in promoting the divergence of the species in both the NE Atlantic and the Mediterranean. The high degree of divergence in the COI dataset (> 7%) suggests the existence of potential cryptic speciation that needs to be further explored with a more comprehensive sampling. Such patterns are only congruent with a scenario where C. calyculata populations were maintained during glacial/interglacial cycles, supporting the role of the studied archipelagos as drivers of diversity for marine biota. We stress the importance of developing studies for species with various life history and dispersal modes. In such a way, a more profound understanding of the biogeographic and evolutionary significance of oceanic islands can catalyse directed conservation efforts, especially in the context of the ongoing climate crisis.

Combining the pieces: identifying key determinants of export diversification in Africa amidst model uncertainty

AbstractExport diversification can be a driver of economic growth. Policies to diversify exports attempt to defy an existing comparative advantage in low-value-added goods to promote transformation. Many structural, general policy, and trade-related variables have been identified as important drivers of diversification. This article reviews the literature on the determinants of export diversification and applies Bayesian Model Averaging (BMA) to empirically tackle model uncertainty stemming from many possible determinants. It assesses the relevance and impact of up to 46 drivers of export diversification for up to 47 African countries and 123 trading partners from 1995 to 2018. It finds that African countries’ structural features are especially influential in determining export diversification, a potential explanation for Africa’s more concentrated export baskets compared to other world regions. Furthermore, trade policies, like tariffs and regional integration, are critical in promoting export diversification. These findings underscore the AfCFTA’s potential to foster export diversification across African economies. A diverse set of non-trade-related policy variables also significantly affect export diversification. Factors such as institutions, education, service sector, resource rents, financial development, FDI and exchange rate stability are relevant determinants in different settings. Moreover, the analysis shows that whom you trade with is also important for diversification, and that context-specific differences, such as specific regional integration contexts or type of commodity-dependence, matter. The results suggest that the goals to diversify exports at the extensive margin for structural change and the intensive margin to tackle volatility, seem often not achievable via the same policies.

Cities Shape the Diversity and Spread of Nonnative Species

The globalization of trade and increased human mobility have facilitated the introduction and spread of nonnative species, posing significant threats to biodiversity and human well-being. As centers of global trade and human populations, cities are foci for the introduction, establishment, and spread of nonnative species. We present a global synthesis of urban characteristics that drive biological invasions within and across cities, focusing on four axes: (a) connectivity, (b) physical properties, (c) culture and socioeconomics, and (d) biogeography and climate. Urban characteristics such as increased connectivity within and among cities, city size and age, and wealth emerged as important drivers of nonnative species diversity and spread, while the relative importance of biogeographic and climate drivers varied considerably. Elaborating how these characteristics shape biological invasions in cities is crucial for designing and implementing strategies to mitigate the impacts of invasions on ecological systems and human well-being.

Elevational patterns and drivers of taxonomic and phylogenetic diversity of pteridophytes: A case study from the Himalaya

In recent times of global biodiversity crisis, documenting the distribution patterns of regional biodiversity and unravelling the drivers that shape these patterns has assumed urgent research priority. In mountains, understanding the distribution of biodiversity along elevational gradients is crucial to its conservation, restoration, and sustainable use. In the Himalaya – highest mountain range in the world – although studies focusing on the elevational distribution of higher plants (angiosperms and gymnosperms) are available, however such studies on lower plants such as pteridophytes are largely lacking. To fill this knowledge gap, here we investigate the elevational patterns of taxonomic and phylogenetic diversity of pteridophytes and their bioclimatic drivers in Jammu and Kashmir. We compiled a comprehensive dataset on 225 pteridophyte species of the study region. We divided the elevation gradient in the study region into 43 vertical bands, each with a width of 100 meters. We used regression analysis to assess the relationship of species richness (SR), standardized effect sizes of phylogenetic diversity (PDses), mean pairwise distance (MPDses), and mean nearest taxon distance (MNTDses) with the elevation. Our results revealed a mid-elevational peak in species richness and a half U-shaped curve in phylogenetic structure along the elevational gradient. We found phylogenetic clustering more or less at mid- and high-elevational bands and phylogenetic overdispersion at low-elevation bands. Taxonomic and phylogenetic ꞵ-diversity was mainly governed by species turnover component. Further, the precipitation-related climatic variables explained a greater proportion of the variation in SR compared to temperature-related variables; but converse was true for PDses, MPDses, and MNTDses, thereby indicating that niche conservatism and environmental filtering shape the composition of pteridophytes along the elevation in this Himalayan region. Overall, the findings of the present study advance our understanding about the elevational distribution patterns in pteridophytes with wide implications for ecology, evolution and biogeography of mountain biodiversity.

Climate, predation, and the controls of island lizard abundance and community structure

AbstractAlternative ecological theories make divergent predictions about the relationship between predators and their prey. If predators exert top‐down ecosystem control, increases in predation should diminish prey abundance and could either diminish or enhance community diversity of prey species. However, if bottom‐up ecosystem controls predominate, predator populations should track underlying variation in prey diversity and abundance, which ultimately should reflect available energy. Past research, both across islands and comparing islands with the mainland, has frequently invoked the importance of predation in regulating lizard abundance and diversity, suggesting an important role of top‐down control when predators are present. However, others have posited a stronger role of food limitation, via competition or bottom‐up forces. If top‐down control predominates, then negative correlations between prey abundance and predator occurrence should emerge within and among islands. Using data from eBird, we inferred landscape‐level presence data for bird species on the islands of Jamaica and Hispaniola. By summing occurrence probabilities of all known anole‐predator birds, we estimated total avian predation pressure and combined these estimates with anole community data from a mark‐recapture study that spanned spatial and climatic gradients on both islands. Avian predators and anole lizards were both affected by climate, with total predator occurrence, anole abundance and anole species richness increasing with mean annual temperature. Anole abundance and predator occurrence showed a curvilinear relationship, where abundance and predator occurrence increased together until predator occurrence became sufficiently high that anole abundance was negatively impacted. This indicates that bottom‐up ecosystem controls drive richness of both anoles and their predators, mitigating the negative effects predators might have on their prey, at least until predator occurrence reaches a threshold. We did not detect consistent evidence of predator occurrence reducing anole community richness. These findings support past research showing that islands with more predators tend to have lower prey abundances, but it does not seem that these top‐down forces are strongly limiting species coexistence. Instead, bottom‐up forces linked with climate may be more important drivers of diversity in both lizards and their avian predators on these islands.

The swash zone selects functionally specialized assemblages of beach interstitial meiofauna (Platyhelminthes, Proseriata)

Life is not a beach for those animals that survive in the rough ecological conditions found in marine sandy beaches – and yet, microscopic animals thrive on them. We explore the drivers for meiofaunal diversity in beaches by analysing taxonomic and functional patterns of 348 flatworm communities across 116 reflective beaches in the western Mediterranean, totalling 152 species (61.2% new to science). First, we confirm that species richness does not differ between beach hydrodynamic levels (swash, shoaling and surf) but rather depends on the characteristics of each beach. Second, we demonstrate that species composition across those levels depends on the species traits, in addition to geographical and abiotic factors. Third, we highlight that the species functional space has a lower richness than expected and a lower redundancy in the wave‐exposed swash level compared to the shoaling and subtidal levels, suggesting a trait‐based ecological filtering. Finally, we show that those differences depend on the higher frequency of hydrodynamics‐related traits in the species of the swash level. Our results suggest that the rough hydrodynamic conditions in the swash level favour a unique combination of species traits, which might be linked to ecological speciation in flatworms but also in other interstitial animals.

V- and VL-Scores Uncover Viral Signatures and Origins of Protein Families.

Viruses are key drivers of microbial diversity, nutrient cycling, and co-evolution in ecosystems, yet their study is hindered due to challenges in culturing. Traditional gene-centric methods, which focus on a few hallmark genes like for capsids, miss much of the viral genome, leaving key viral proteins and functions undiscovered. Here, we introduce two powerful annotation-free metrics, V-score and VL-score, designed to quantify the "virus-likeness" of protein families and genomes and create an open-access searchable database, 'V-Score-Search'. By applying V- and VL-scores to public databases (KEGG, Pfam, and eggNOG), we link 38-77% of protein families with viruses, a 9-16x increase over current estimates. These metrics outperform existing approaches, enabling precise detection of viral genomes, prophages, and host-derived auxiliary viral genes (AVGs) from fragmented sequences, and significantly improving genome binning. Remarkably, we identify up to 17x more AVGs, dominated by non-metabolic proteins of unknown function. This innovation unlocks new insights into virus signatures and host interactions, with wide-ranging implications from genomics to biotechnology.

The kinase ATR controls meiotic crossover distribution at the genome scale in Arabidopsis

Abstract Meiotic crossover, i.e. the reciprocal exchange of chromosome fragments during meiosis, is a key driver of genetic diversity. Crossover is initiated by the formation of programmed DNA double-strand breaks (DSBs). While the role of ATAXIA-TELANGIECTASIA AND RAD3-RELATED (ATR) kinase in DNA damage signaling is well-known, its impact on crossover formation remains understudied. Here, using measurements of recombination at chromosomal intervals and genome-wide crossover mapping, we showed that ATR inactivation in Arabidopsis (Arabidopsis thaliana) leads to dramatic crossover redistribution, with an increase in crossover frequency in chromosome arms and a decrease in pericentromeres. These global changes in crossover placement were not caused by alterations in DSB numbers, which we demonstrated by analyzing phosphorylated H2A.X foci in zygonema. Using the seed-typing technique, we found that hotspot usage remains mainly unchanged in atr mutants compared with wild-type individuals. Moreover, atr showed no change in the number of crossovers caused by two independent pathways, which implies no effect on crossover pathway choice. Analyses of genetic interaction indicate that while the effects of atr are independent of MMS AND UV SENSITIVE81 (MUS81), ZIPPER1 (ZYP1), FANCONI ANEMIA COMPLEMENTATION GROUP M (FANCM), and D2 (FANCD2), the underlying mechanism may be similar between ATR and FANCD2. This study extends our understanding of ATR's role in meiosis, uncovering functions in regulating crossover distribution.

The influence of plant genomics on plant evolution

With the increasing demand for high-quality tea, the genetic basis of ideal traits of tea plants has been widely concerned. The research on tea tree genomics, specifically focusing on “Longjing 43”, provides significant insights into plant evolution and breeding. “Longjing 43” was chosen due to its complex genome and economic importance. The study successfully assembled its genome to the chromosome level, revealing a large and heterogeneous genome with numerous repetitive sequences. Comparative genomics showed that hybridization has been a key driver of genetic diversity and adaptability in tea plants. These findings are crucial for developing marker-assisted selection (MAS) techniques, improving traits such as disease resistance, flavor, and stress response. Moreover, the research underscores the role of tea tree genomics in preserving cultural heritage and promoting economic benefits through enhanced tea quality. This study contributes to the broader understanding of plant genomics by illustrating the evolutionary processes and potential applications in agriculture, conservation, and industry, thus offering a comprehensive tool for future plant breeding and genetic improvement strategies.

Scale‐Dependent Drivers of Air‐Sea CO2 Flux Variability

AbstractIn climate studies, it is crucial to distinguish between changes caused by natural variability and those resulting from external forcing. Here we use a suite of numerical experiments based on the ECCO‐Darwin ocean biogeochemistry model to separate the impact of the atmospheric carbon dioxide (CO2) growth rate and climate on the ocean carbon sink — with a goal of disentangling the space‐time variability of the dominant drivers. When globally integrated, the variable atmospheric growth rate and climate exhibit similar magnitude impacts on ocean carbon uptake. At local scales, interannual variability in air‐sea CO2 flux is dominated by climate. The implications of our study for real‐world ocean observing systems are clear: in order to detect future changes in the ocean sink due to slowing atmospheric CO2 growth rates, better observing systems and constraints on climate‐driven ocean variability are required.

Specificity determinants of pathogens in forest

Abstract Host‐specific pathogens have long been suggested to act as a major driver of species diversity in tropical forests. However, determining the degree of host specificity of potential pathogens coupled to key cellular characteristics of infection is difficult and time‐consuming. These challenges have delayed progress in relating the functional specificity of pathogenic fungi to ecological consequences. We tested the pathogenicity of 27 (of 215) fungi that were isolated from surface sterilized roots of seedlings from four common tree species in a diverse subtropical forest. Inoculation experiments showed that six fungi exhibited strong pathogenicity on the host seedlings. Five of these only infected their specific hosts (i.e. host‐specific pathogen species). Green fluorescent protein labelling revealed that in three host‐specific pathogens fungal hyphae were able to grow into the vascular tissues only in their specific host plant, in contrast to other fungal‐host combinations that exhibit non‐pathogenic interactions. This fluorescent labelling technique allows direct tracking of the progress of fungal infection in different host tissues. Synthesis. By coupling the green fluorescent protein technique with standard host inoculation experiments, we determined the developmental differences between infections by pathogenic and non‐pathogenic fungi in a relatively simple and straightforward way. Our work provides a useful tool for rapidly screening and categorizing host–fungal interactions, reflecting the functional basis of host specificity of pathogenic fungi. More broadly, this technique can contribute to understanding the roles of pathogens in species coexistence and biodiversity maintenance in forest communities.