Species Pool Research Articles

Illuminating Plant Community Assembly on Karst Mountain Road Slopes through Plant Traits and Environmental Filters

Understanding how assembly processes shape local plant assemblages from the potential species pool is crucial for biodiversity conservation and revegetation. Mountainous regions are global biodiversity hotspots with high levels of diversity, concentration, and vulnerability. Road construction in these areas poses ecological challenges, including habitat loss and reduced biodiversity. Feature-based ecology highlights non-biological filtering as a key driver of habitat-specific community formation. Analyzing trait structures and their association with the environment can reveal community assembly processes under specific environmental conditions. However, quantifying species-environment-traits interactions during community assembly on roadside slopes is still underexplored. In our study, 76 naturally recovered roadside slopes, 656 self-established plant communities and 113 plant species across ten functional traits, along with their environmental associations, in the karst mountain region of southwestern China, were examined. Our findings show that there are still abundant native plants with colonization potential settled on steep roadside slopes in karst mountain areas. Diffusion constraints stemming from distance to the core species pool, elevation, and differences in adjacent vegetation types emerged as key factors causing variations in species composition of self-established communities. The slope environment exerts strong selective pressures leading to a convergence pattern in traits related to dispersal and colonization while showing a divergence pattern in traits linked to competitive strategies and regeneration. These findings identify critical functional traits and environmental factors shaping roadside plant communities and illustrate the predictability of environmental filtering and fundamental community assembly. Overall, our study sheds light on the intricate interactions among assembly processes, functional traits, and environmental factors driving local plant assemblages in mountainous regions, providing insights for effective diversity conservation and revegetation strategies.

Highly pathogenic avian influenza: Considerations for vaccination and implications for international trade. A primary breeder’s perspective. Proceeding of The First International Avian Influenza Summit, University of Arkansas- October 16-17, 2023"

Vaccination against avian influenza requires the assessment of multiple technical, legislative, and trade aspects related to its epidemiology and the country’s veterinary infrastructure, commerce policies, and interests. According to the World Organization of Animal Health (WOAH), vaccination against AI should not preclude a country from eligibility for trade as long as it can prove freedom from natural infection. Importing countries may have policies above the general guidelines offered by WOAH; however. Whether living with the disease for a long(er) time, having to adjust vaccines to better protect against newer avian influenza virus variants or clades, and/or whether there are indemnity incentives available to compensate growers for the losses related to outbreaks, considerations pertaining to the geographic spread of the disease across the country’s territory, the sector(s) of the poultry industry being affected, and whether all alternatives to combat the disease have been explored, and perhaps exhausted, should also be taken into consideration. WOAH’s guidelines for the continuation of trade include zoning that limits restrictions to a geographical area (10 km, county, or state) instead of the entire country. Compartmentalization also offers another approach to the continuation of trade for premises that demonstrate robust biosecurity and management programs backed by testing to demonstrate freedom from infection. Alternatives to avoid or reduce waste products (e.g., meat and eggs) should also be considered according to implications to the risk involved of further spread onto other avian and poultry populations. Considering the fact that the 2.3.4.4b clade has been able to infect a large number of wild bird and mammalian species and, at least for countries where the disease is not endemic in its commercial sectors, vaccinating only poultry, at least in countries with low prevalence and incidence rate would not prevent the spread of the disease amongst that large pool of susceptible animal species. For this latter aspect, perhaps vaccination strategies would be more effective if developed towards mitigating prevalence in the natural reservoirs. This implies developing vaccines capable of being deployed in mass. In the large scheme of things and within the one-health concept, this latter approach may have a larger impact on combatting high pathogenicity avian influenza.

Global flows of insect transport and establishment: The role of biogeography, trade and regulations

AbstractAimNon‐native species are part of almost every biological community worldwide, yet numbers of species establishments have an uneven global distribution. Asymmetrical exchanges of species between regions are likely influenced by a range of mechanisms, including propagule pressure, native species pools, environmental conditions and biosecurity. While the importance of different mechanisms is likely to vary among invasion stages, those occurring prior to establishment (transport and introduction) are difficult to account for. We used records of unintentional insect introductions to test (1) whether insects from some biogeographic regions are more likely to be successful invaders, (2) whether the intensity of trade flows between regions determines how many species are intercepted and how many successfully establish, and (3) whether the variables driving successful transport and successful establishment differ.LocationCanada, mainland USA, Hawaii, Japan, Australia, New Zealand, Great Britain, South Korea, South Africa.MethodsTo disentangle processes occurring during the transport and establishment stages, we analysed border interceptions of 8199 insect species as a proxy for transported species flows, and lists of 2076 established non‐native insect species in eight areas. We investigated the influence of biogeographic variables, socio‐economic variables and biosecurity regulations on the size of species flows between regions.ResultsDuring transport, the largest species flows generally originated from the Nearctic, Panamanian and Neotropical regions. Insects native to 8 of 12 biogeographic regions were able to establish, with the largest flows of established species on average coming from the Western Palearctic, Neotropical and Australasian/Oceanian regions. Both the biogeographic region of origin and trade intensity significantly influenced the size of species flows between regions during transport and establishment. The transported species richness increased with Gross National Income in the source country, and decreased with geographic distance. More species were able to establish when introduced within their native biogeographic region.Main ConclusionsOur results suggest that accounting for processes occurring prior to establishment is crucial for understanding invasion asymmetry in insects, and for quantifying regional biosecurity risks.

The butterflies and burnets (Lepidoptera: Hesperiidea, Lycaenidae, Nymphalidae, Papilionidae, Pieridae, Zygaenidae) of the Nature Reserve Bosco della Fontana (Lombardy, Italy)

Insects are declining at an alarming rate in many parts of Europe and this also applies to butterflies, one of the most well-studied groups of insects. They are popular with the public and are considered good biodiversity indicators. Bosco Fontana, an isolated protected area, which contains one of the best preserved lowland forests of northern Italy, is surrounded by a highly modified landscape and is known to host some important butterfly populations. To investigate the butterflies and burnets, a total of 22 standard surveys, lasting 25 minutes each, were carried out in four different habitat types of Bosco Fontana in the years 2020 and 2021. The surveys confirmed the presence of 36 species of butterflies and 3 species of burnets for the reserve. Statistical analysis revealed that the butterfly and burnet assemblages of the grasslands, ecotones and forests were distinct, but similar in the two study years (datasets available as supplementary information). Many nemoral species were confirmed for Bosco Fontana, with relict populations of Favonius quercus and Argynnis paphia present only in a few residual forests in the Po Plain. Five species typical of grasslands and other open habitats and belonging to the local species pool of the Po Plain in the province of Mantua, were never detected at Bosco Fontana in the study years. The ecological significance of their absence is discussed.

Herbaceous ornamental plants with conspicuous aesthetic traits contribute to plant invasion risk in subtropical urban parks

Global ornamental horticulture is a major pathway for plant invasions, while urban parks are key areas for introducing non-native ornamental plants. To react appropriately to the challenges (e.g., biological invasion issues) and opportunities (e.g., urban ecosystem services) of herbaceous ornamentals in urban parks, we conducted a comprehensive invasive risk assessment in 363 urban parks in Chongqing, a subtropical city in China. The results found more than 1/3 of the 119 non-native species recorded in urban parks had a high invasion risk, and more than five species had potential invasion risk in 96.29% of the study area, indicating herbaceous ornamentals in urban parks are potentially a pool of invasive species that deserves attention. Moreover, humans have chosen herbaceous ornamentals with more aesthetic characteristics in urban parks, where exotic species were more prominent than native species in floral traits, such as more conspicuous flowers and longer flowering periods. The findings can inform urban plant management, provide an integrated approach to assessing herbaceous ornamentals' invasion risk, and offer insights into understanding the filtering effects of human aesthetic preferences.

Niche overlap and Hopfield-like interactions in generalized random Lotka-Volterra systems.

We study communities emerging from generalized random Lotka-Volterra dynamics with a large number of species with interactions determined by the degree of niche overlap. Each species is endowed with a number of traits, and competition between pairs of species increases with their similarity in trait space. This leads to a model with random Hopfield-like interactions. We use tools from the theory of disordered systems, notably dynamic mean-field theory, to characterize the statistics of the resulting communities at stable fixed points and determine analytically when stability breaks down. Two distinct types of transition are identified in this way, both marked by diverging abundances but differing in the behavior of the integrated response function. At fixed points only a fraction of the initial pool of species survives. We numerically study the eigenvalue spectra of the interaction matrix between extant species. We find evidence that the two types of dynamical transition are, respectively, associated with the bulk spectrum or an outlier eigenvalue crossing into the right half of the complex plane.

Rarefaction and extrapolation with beta diversity under a framework of Hill numbers: The iNEXT.beta3D standardization

AbstractBased on sampling data, we propose a rigorous standardization method to measure and compare beta diversity across datasets. Here beta diversity, which quantifies the extent of among‐assemblage differentiation, relies on Whittaker's original multiplicative decomposition scheme, but we use Hill numbers for any diversity order q ≥ 0. Richness‐based beta diversity (q = 0) quantifies the extent of species identity shift, whereas abundance‐based (q > 0) beta diversity also quantifies the extent of difference among assemblages in species abundance. We adopt and define the assumptions of a statistical sampling model as the foundation for our approach, treating sampling data as a representative sample taken from an assemblage. The approach makes a clear distinction between the theoretical assemblage level (unknown properties/parameters of the assemblage) and the sampling data level (empirical/observed statistics computed from data). At the assemblage level, beta diversity for N assemblages reflects the interacting effect of the species abundance distribution and spatial/temporal aggregation of individuals in the assemblage. Under independent sampling, observed beta (= gamma/alpha) diversity depends not only on among‐assemblage differentiation but also on sampling effort/completeness, which in turn induces dependence of beta on alpha and gamma diversity. How to remove the dependence of richness‐based beta diversity on its gamma component (species pool) has been intensely debated. Our approach is to standardize gamma and alpha based on sample coverage (an objective measure of sample completeness). For a single assemblage, the iNEXT method was developed, through interpolation (rarefaction) and extrapolation with Hill numbers, to standardize samples by sampling effort/completeness. Here we adapt the iNEXT standardization to alpha and gamma diversity, that is, alpha and gamma diversity are both assessed at the same level of sample coverage, to formulate standardized, coverage‐based beta diversity. This extension of iNEXT to beta diversity required the development of novel concepts and theories, including a formal proof and simulation‐based demonstration that the resulting standardized beta diversity removes the dependence of beta diversity on both gamma and alpha values, and thus reflects the pure among‐assemblage differentiation. The proposed standardization is illustrated with spatial, temporal, and spatiotemporal datasets, while the freeware iNEXT.beta3D facilitates all computations and graphics.

Leaf functional traits vary among growth forms and vegetation zones in the Himalaya

Compression of life zones along elevational gradients in mountains supports diverse vegetation types, and therefore offers ideal setting to study plant functional traits. Functional traits, the features that enable plants to live in varied environmental conditions, help in understanding ecological interactions, evolutionary adaptations, and predicting plant response to global change drivers. To date, little is known how the trait diversity varies across different growth forms and vegetation zones in mountains. Here, we aimed to investigate interspecific leaf trait variability among different growth forms and vegetation zones along a wide elevation gradient (2000–4200 m) in Kashmir Himalaya. We measured leaf functional traits (specific leaf area—SLA, leaf thickness — LT, leaf dry matter content —LDMC) of 76 plant species corresponding to three growth forms (trees, shrubs and herbs) and three vegetation zones (Himalayan dry temperate forests, subalpine forests and alpine grasslands). Our results revealed high trait variability across the regional species pool studied. We found significant variation in leaf functional traits among the different growth forms, with higher values of LT and LDMC recorded for woody species than herbaceous ones. Among different vegetation zones, the SLA was found to be significantly higher at lower to middle elevations, while the other leaf traits (LT and LDMC) showed an opposite trend. Across all the vegetative zones, we also found a negative correlation between SLA and the other leaf traits, and the latter showed a positive trait-trait correlation. Overall, our study contributes to a deeper understanding of trait-trait, trait-growth form and trait-vegetation zone relationships. Our findings suggest that the variation in leaf functional traits among different growth forms seems to be a trade-off mechanism between resource acquisition and leaf construction, and also help in identifying species' adaptive functional traits that are critical for plant survival in the face of ongoing climate change in the Himalaya.

The effect of riparian forest on landscape connectivity for the EPT community across European regions

AbstractEphemeroptera, Plecoptera and Trichoptera are three orders of freshwater macroinvertebrates with a short terrestrial adult life-stage that they use to disperse by flying upstream. This aerial dispersal can be assisted by native riparian forest, but regional variation has not yet been empirically tested. In this study we compared the EPT community of 153 sampling sites located in freshwater streams in four European regions (Central Plains, Central Highlands, Alps, Iberia). In each site, we assessed the EPT community dispersal ability using the Species Flying Propensity index. We also calculated the native deciduous forest cover in the riparian buffer and several environmental stressors such as saprobic pollution or catchment anthropization. Finally, we tested which of these parameters have a significant effect on the EPT community. In the Central Highlands and in Iberia, the share of weak dispersers increased with native deciduous forest cover, indicating a positive effect on dispersal of EPTs. In the Central Plains and the Alps, no such effect was found. We conclude that the effect of native deciduous forest depends on regional landscape characteristics and the regional species pool, but considering the dispersal of the regional EPT communities is needed to create effective river management policies.

L. pneumophila resists its self-harming metabolite HGA via secreted factors and collective peroxide scavenging.

Before environmental opportunistic pathogens can infect humans, they must first successfully grow and compete with other microbes in nature, often via secreted antimicrobials. We previously discovered that the bacterium Legionella pneumophila, the causative agent of Legionnaires' disease, can compete with other microbes via a secreted molecule called HGA. Curiously, L. pneumophila strains that produce HGA is not wholly immune to its toxicity, making it a mystery how these bacteria can withstand the "friendly fire" of potentially self-targeting antimicrobials during inter-bacterial battles. Here, we identify several strategies that allow the high-density bacterial populations that secrete HGA to tolerate its effects. Our study clarifies how HGA works. It also points to some explanations of why it is difficult to disinfect L. pneumophila from the built environment and prevent disease outbreaks.

Plant Responses to Global Climate Change and Urbanization: Implications for Sustainable Urban Landscapes

Global warming has led to irregular precipitation patterns and various abiotic and biotic stresses, resulting in unforeseen consequences for wildlife. Plant species are particularly vulnerable to these global climate changes, struggling to adapt to the increasing stressors. Urban environments exacerbate these challenges, further hindering plant survival and growth. The declining number of climate- and urban-tolerant plant species is a direct consequence of escalating stresses. However, resistance breeding approaches coupled with environmentally friendly technologies like biostimulants offer hope by expanding the pool of adaptable species. Urban vegetation plays a vital role in mitigating the urban heat island effect, supporting mental well-being among residents, and preserving biodiversity. In this study, we comprehensively review recent research findings on these topics with a focus on publications from the past 5 years. Emphasizing stress-tolerant ornamental urban plants including trees and herbaceous species becomes crucial for establishing sustainable living practices. By incorporating resilient plant varieties into urban landscapes, we can enhance ecological balance while improving the overall quality of urban environments for both human inhabitants and wildlife populations.

Exotic success following disturbance explained by weak native resilience and ruderal exotic bias

Abstract Disturbance is a primary driver of exotic plant invasions, but why disturbance commonly favours exotics over natives is unresolved. To address this question, we conducted the first biogeographic study of disturbance across multiple plant species. We experimentally disturbed grasslands and added seeds of 34 plant species to plots in their native range and in two introduced ranges that differed in invasibility (susceptibility to invasion) to evaluate recruitment while examining potential influences of resource availability, native community recovery from disturbance (resilience) and life‐history traits in local species pools. Species pools in the native (donor) range were more strongly skewed towards ruderal taxa than species pools in the introduced ranges. This bias in the donor pool was exacerbated by introduction filters that further selected for ruderal traits, strongly skewing exotic species pools in the introduced ranges towards ruderals. Sown species, which reflected these trait patterns, benefited from disturbance universally, but their disturbance response was 10‐fold greater in the more invasible introduced range. This result was not explained by nutrient availability, which responded similar to disturbance across ranges. Nor was it driven by background propagule pressure, which was minimal. Rather, the exaggerated disturbance effect in the more invasible introduced range appeared to be driven by weak recovery of the native plant community that allowed ruderal‐biased exotics to proliferate. Overall, disturbance appeared to favoured exotics because they were much more likely than natives to be ruderal. However, this trait bias only corresponded with an invader advantage in the more invasible range where weak community resilience was linked to slow‐growing, stress‐tolerant natives that failed to rapidly recover space and resources. In contrast, in the less invasible introduced range, highly competitive native perennials quickly filled the disturbance gap, demonstrating high community resilience that appeared to limit invader recruitment. Synthesis: Biogeographic influences on local species pools can facilitate invader success following disturbance, but final invasion outcomes are conditioned by native community resilience.

Soil seed banks provide a storage effect in post-logging regrowth forests of southeastern Australia

Despite the importance of soil seed banks in diversity maintenance, our understanding of plant response to changes in resource availability is largely limited to above-ground vegetation. We investigated how forest structure and edaphic properties influenced the above-ground vegetation and soil seed banks following logging in montane regrowth forests dominated by Eucalyptus regnans in the Central Highlands of southeastern Australia. We surveyed above-ground vegetation, soil seed banks, forest structure and soil properties across 20 harvest units, aged 16 to 20 years. A total of 80 species were identified in above-ground vegetation with 72 species in the soil seed bank, with only 34% of species co-occurring in both species’ pools. Climate, soil, topography, and light availability shaped plant composition but the relative importance of these properties varied among individual species and pools of diversity (combined, above-ground, soil seed bank, life form). Annual heat moisture index (AHMI) was the most important factor that influenced plant community composition across all species pools with individual species positively associated with AHMI. Acacia, but not Eucalyptus stem density further moderated plant response via effects on both light availability and soil nitrogen at the stem exclusion phase of stand development. Structurally mediated controls on above-ground community composition flow through to the soil seed bank via above-ground diversity effects on below-ground composition. For the combined species pool, individual species were most frequently related to Acacia stem density that on average explained 20% of model variation. Soil nutrients accounted for most of the model variation for individual species in above-ground (26%), soil seed bank (20%) and non-woody (32%) pools of diversity, with AHMI accounting for most of the model variation for woody species (18%). The differential response of individual species and community composition to gradients in resource availability across different pools of species diversity and life forms clearly demonstrates a storage effect in wet temperate forests of southeastern Australia that promotes post-disturbance recruitment and persistence. Our work suggests logging interacts with broad environmental controls to shape species diversity. The key role of Acacia stem density as a biotic filter of plant diversity provides opportunity to shape future plant diversity through management interventions such as thinning in the early stages of stand development. With native forest harvesting of these forests set to end from 2024, our findings provide important information on future patterns of plant diversity as logged forests recover over time, opportunities for management interventions in shaping plant composition, and potential impacts of future wildfire.

Urbanization, climate and species traits shape mammal communities from local to continental scales.

Human-driven environmental changes shape ecological communities from local to global scales. Within cities, landscape-scale patterns and processes and species characteristics generally drive local-scale wildlife diversity. However, cities differ in their structure, species pools, geographies and histories, calling into question the extent to which these drivers of wildlife diversity are predictive at continental scales. In partnership with the Urban Wildlife Information Network, we used occurrence data from 725 sites located across 20 North American cities and a multi-city, multi-species occupancy modelling approach to evaluate the effects of ecoregional characteristics and mammal species traits on the urbanization-diversity relationship. Among 37 native terrestrial mammal species, regional environmental characteristics and species traits influenced within-city effects of urbanization on species occupancy and community composition. Species occupancy and diversity were most negatively related to urbanization in the warmer, less vegetated cities. Additionally, larger-bodied species were most negatively impacted by urbanization across North America. Our results suggest that shifting climate conditions could worsen the effects of urbanization on native wildlife communities, such that conservation strategies should seek to mitigate the combined effects of a warming and urbanizing world.

Salinity as a Factor Limiting the Crustacean Potential Taxonomic Richness in the World’s Hypersaline Water Ecosystems: a Review

Crustaceans are one of the biosphere’s most diverse and successful groups, also inhabiting various extreme habitats. Summing up our data and 203 literary sources, we analyzed how the degree of environmental extremeness can limit the potential taxonomic richness of crustaceans using the example of hypersaline waters. An analysis showed that, with an increase in salinity, the number of classes and orders of the Crustacea subtype decreased linearly, while the number of genera and species decreased exponentially. It has been established that with an increase in environmental salinity, the contribution of Arthropoda species to the total species richness of animals in hypersaline waters increases from 49 to 100%, the gift of Crustacea species to the total species richness of Arthropoda increases from 66 to 78%, and the contribution of Branchiopoda to the species richness of Crustacea from 19 to 71%. In the Crimean hypersaline water bodies, in the range from 35 to 120 g/L, salinity is not the main factor determining the species richness and composition of the fauna, the combination of all other factors, primarily biotic ones, plays a more critical role. Only at higher values, salinity itself begins to play the role of a hard-environmental filter. Salinity growing above 35 g/L reduces the comfort of the environment for animals and filters out the pool of species that can exist in the ecosystem. In particular water bodies, the realization of this possibility depends not only on salinity but also on the existing biotic relationships and the entire set of abiotic factors.

Effects of 1-nitropropane on pyrolysis of n-hexane at atmospheric pressure

In order to investigate the effects of 1-nitropropane (1-NP) on the pyrolysis of n-hexane, the pyrolysis processes of pure n-hexane and n-hexane/1-NP mixture in a jet-stirred reactor (JSR) were experimentally studied at atmospheric pressure with the technique of synchrotron ultraviolet photoionization mass spectrometry (SVUV-PIMS). The pyrolysis experiments of pure n-hexane and n-hexane/1-NP mixture were performed in the temperature ranges of 673–1143 K and 598–1128 K, respectively. The species pools for the pyrolysis of pure n-hexane and n-hexane/1-NP mixture were comprehensively determined and 25 species for pyrolysis of pure n-hexane versus 18 species for pyrolysis of n-hexane/1-NP mixture were identified. Based on the photoionization mass spectra scanned at different photon energies, the mole fraction profiles of all the pyrolysis species were evaluated. The experimental results showed that the initial pyrolysis temperature of n-hexane was observably reduced by 75 K with the addition of 1-NP, and the initial formation temperatures (IFTs) of some major pyrolysis products and important intermediates were correspondingly reduced. A high degree of conformity in the species pools of the pyrolysis of pure n-hexane and n-hexane/1-NP mixture (at both low and atmospheric pressures) was observed. On the basis of the experimental observations, modeling simulations and mechanisms proposed in previous studies, the low-temperature mechanisms for the 1-NP-initiated pyrolysis of n-hexane were discussed. A mechanism, including unimolecular dissociation reactions of 1-NP, radical reactions to produce highly active radicals, H-abstraction reactions of n-hexane and subsequent C-C bond dissociation reactions of hexyl radicals, was proposed.

River connectivity increases the diversity of fish communities in gravel pit lakes

AbstractObjectiveOff‐channel floodplain features are important components of a river system that provide habitat and boost regional species pools, but river–floodplain connectivity is disrupted by anthropogenic activities. The Campbell Lakes in Harrison, Ohio, are formerly isolated gravel pits along the Whitewater River and are connected to the river through flooding‐related erosion. The lakes were first stocked with sport fish by Great Parks of Hamilton County to promote recreational fishing, but stocking ended in 2019 due to frequent connection with the Whitewater River during high flow. We explored how the fish community composition of the Campbell Lakes reflects increasing connectivity with the Whitewater River and among the lakes.MethodsUsing historical aerial photographs and river discharge estimates, we established an approximate timeline of permanent connectivity and potential breaches between the lakes and the Whitewater River from 2000 to 2020. Fish community data collected via electrofishing surveys of the Campbell Lakes in 2004, 2007, 2012, and 2020 were compared to data from surveys of the Whitewater and Great Miami rivers in 1995 and 2013.ResultThe lakes were dominated by centrarchid species in early surveys but showed increased species and family richness with time. Based on an analysis of similarity and nonmetric multidimensional scaling, the lakes' fish communities differed significantly among years and gradually increased in resemblance to the river communities.ConclusionOur results suggest that the Campbell Lakes fish communities are broadening to include taxa from the Whitewater and Great Miami River communities and are shifting from lentic to lotic species. The change in fish community assemblages in the Campbell Lakes demonstrates the potential for gravel pit lakes to serve as artificial floodplain features that can enhance river–floodplain connectivity.

Intraspecific variation in realized dispersal probability and host quality shape nectar microbiomes.

Epiphytic microbes frequently affect plant phenotype and fitness, but their effects depend on microbe abundance and community composition. Filtering by plant traits and deterministic dispersal-mediated processes can affect microbiome assembly, yet their relative contribution to predictable variation in microbiome is poorly understood. We compared the effects of host-plant filtering and dispersal on nectar microbiome presence, abundance, and composition. We inoculated representative bacteria and yeast into 30 plants across four phenotypically distinct cultivars of Epilobium canum. We compared the growth of inoculated communities to openly visited flowers from a subset of the same plants. There was clear evidence of host selection when we inoculated flowers with synthetic communities. However, plants with the highest microbial densities when inoculated did not have the highest microbial densities when openly visited. Instead, plants predictably varied in the presence of bacteria, which was correlated with pollen receipt and floral traits, suggesting a role for deterministic dispersal. These findings suggest that host filtering could drive plant microbiome assembly in tissues where species pools are large and dispersal is high. However, deterministic differences in microbial dispersal to hosts may be equally or more important when microbes rely on an animal vector, dispersal is low, or arrival order is important.

Signs of rapid evolution in an invasive forest species: Drivers of the incipient neutral, adaptive and phenotypic divergence

Evolutionary forces such as genetic drift and natural selection operate during the process of biological invasion. More specifically, nonnative populations suffer genetic and demographic bottlenecks, and are exposed to new environmental, climatic and biotic filters. Thus, neutral and/or adaptive drivers may contribute to genetic differentiation of the introduced germplasm. We hypothesize that the gene pool of fire-adapted species that become invasive in fire-prone ecosystems may differ from that of originally planted and native one because of novel selective forces and founder effects. Genetic impoverishment due to genetic drift could also be buffered by demographic processes as the production of a large aerial seed bank by serotiny. We conducted genomic analyses of the world’s most planted tree Pinus radiata using Single Nucleotide Polymorphisms, comparing introduced cohorts with and without fire exposure, and also with one population of the native range. Phenotypic traits of introduced cohorts were assessed for quantitative characters. In the introduced range we found lower expected heterozygosity and nucleotide diversity due to bottlenecks during introduction and commercial selection in orchards. We also detected decreased inbreeding, related to a serotinous seed bank that buffers bottlenecks. We found genomic regions under selection, both in the comparison between native and introduced range, and between introduced cohorts with and without exposure to fire. Within the introduced area, we observed possible fire-mediated diversifying selection for five quantitative traits. Our results show that both neutral and adaptive forces promote early divergence of the introduced species Pinus radiata. Also, fire acts as a rapid selection factor, prompting the incipient adaptive divergence of cohorts recruited after fires, facilitating invasion.

Avian Diversity Responds Unimodally to Natural Landcover: Implications for Conservation Management.

Predicting species' ecological responses to landcovers within landscapes could guide conservation practices. Current modelling efforts derived from classic species-area relationships almost always predict richness monotonically increasing as the proportion of landcovers increases. Yet evidence to explain hump-shaped richness-landcover patterns is lacking. We tested predictions related to hypothesised drivers of peaked relationships between richness and proportion of natural landcover. We estimated richness from breeding bird atlases at different spatial scales (25 to 900 km2) in New York State and Southern Ontario. We modelled richness to gradients of natural landcover, temperature, and landcover heterogeneity. We controlled models for sampling effort and regional size of the species pool. Species richness peaks as a function of the proportion of natural landcover consistently across spatial scales and geographic regions sharing similar biogeographic characteristics. Temperature plays a role, but peaked relationships are not entirely due to climate-landcover collinearities. Heterogeneity weakly explains richness variance in the models. Increased amounts of natural landcover promote species richness to a limit in landscapes with relatively little (<30%) natural cover. Higher amounts of natural cover and a certain amount of human-modified landcovers can provide habitats for species that prefer open habitats. Much of the variation in richness among landscapes must be related to variables other than natural versus human-dominated landcovers.