Predicting future stability of ecosystem functioning under climate change

To maintain food security under global change, we need to consider the stability of ecosystem functioning into the future, particularly in resource production landscapes such as agricultural pasture. With ongoing climate change, extreme climatic events are predicted to become more frequent and severe globally, impacting crop production. The whole process of farming will become more uncertain, from choice of crop and crop productivity to the timing of the windows of opportunity for management decisions. Future agricultural policies, therefore, should not only consider changes in grassland production, but also its future stability. We use a case study of agricultural pastures on the island of Ireland to project different components of ecosystem stability (resistance, recovery time and recovery rate) to 2050 and 2080 under different future climate scenarios: a peak and decline scenario; and a continued emissions scenario. We show that future climate change will have substantial effects on both the future resistance and the recovery of ecosystem functioning following environmental disturbances, but the spatial pattern of effect sizes is not the same for these two measures of stability. National level analyses and agricultural policies, therefore, are likely to ignore regional variation in future change. From this, we encourage the translation of stability-based constructs, as well as maximum yield considerations, into future agricultural policy at the regional level

Ecosystem stability at the landscape scale is primarily associated with climatic history

There is an increasing interest in landscape-scale perspectives of ecosystem functioning to inform policy and conservation decisions. However, we need a better understanding of the stability of ecosystem functioning (e.g. plant productivity) at the landscape scale to inform policy around topics such as global food security. We investigate the role of the ecological and environmental context on landscape-scale stability of plant productivity in agricultural pasture using remotely sensed enhanced vegetation index data. We determine whether four measures of stability (variability, magnitude of extreme anomalies, recovery time and recovery rate) are predicted by (a) species richness of vascular plants, (b) regional land cover heterogeneity and (c) climatic history. Stability of plant productivity was primarily associated with climatic history, particularly a history of extreme events. These effects outweighed any positive effects of species richness in the agricultural landscape. A history of variable and extreme climates both increased and decreased contemporary ecosystem stability, suggesting both cumulative and legacy effects, whereas land cover heterogeneity had no effect on stability. The landscape scale is a relevant spatial scale for the management of an ecosystem's stability. At this scale, we find that past climate is a stronger driver of stability in plant productivity than species richness, differing from results at finer field scales. Management should take an integrated approach by incorporating the environmental context of the landscape, such as its climatic history, and consider multiple components of stability to maintain functioning in landscapes that are particularly vulnerable to environmental change

Resource competition drives an invasion-replacement event among shrew species on an island

Invasive mammals are responsible for the majority of native species extinctions on islands. While most of these extinction events will be due to novel interactions between species (e.g. exotic predators and naive prey), it is more unusual to find incidences where a newly invasive species causes the decline/extinction of a native species on an island when they normally coexist elsewhere in their overlapping mainland ranges. We investigated if resource competition between two insectivorous small mammals was playing a significant role in the rapid replacement of the native pygmy shrew Sorex minutus in the presence of the recently invading greater white-toothed shrew Crocidura russula on the island of Ireland. We used DNA metabarcoding of gut contents from >300 individuals of both species to determine each species' diet and measured the body size (weight and length) during different stages of the invasion in Ireland (before, during and after the species come into contact with one another) and on a French island where both species have long coexisted (acting as a natural ‘control’ site). Dietary composition, niche width and overlap and body size were compared in these different stages. The body size of the invasive C. russula and composition of its diet changes between when it first invades an area and after it becomes established. During the initial stages of the invasion, individual shrews are larger and consume larger sized invertebrate prey species. During later stages of the invasion, C. russula switches to consuming smaller prey taxa that are more essential for the native species. As a result, the level of interspecific dietary overlap increases from between 11% and 14% when they first come into contact with each other to between 39% and 46% after the invasion. Here we show that an invasive species can quickly alter its dietary niche in a new environment, ultimately causing the replacement of a native species. In addition, the invasive shrew could also be potentially exhausting local resources of larger invertebrate species. These subsequent changes in terrestrial invertebrate communities could have severe impacts further downstream on ecosystem functioning and services

Larval Transport Modeling of Deep-Sea Invertebrates Can Aid the Search for Undiscovered Populations

Background: Many deep-sea benthic animals occur in patchy distributions separated by thousands of kilometres, yet because deep-sea habitats are remote, little is known about their larval dispersal. Our novel method simulates dispersal by combining data from the Argo array of autonomous oceanographic probes, deep-sea ecological surveys, and comparative invertebrate physiology. The predicted particle tracks allow quantitative, testable predictions about the dispersal of benthic invertebrate larvae in the south-west Pacific. Principal Findings: In a test case presented here, using non-feeding, non-swimming (lecithotrophic trochophore) larvae of polyplacophoran molluscs (chitons), we show that the likely dispersal pathways in a single generation are significantly shorter than the distances between the three known population centres in our study region. The large-scale density of chiton populations throughout our study region is potentially much greater than present survey data suggest, with intermediate 'stepping stone' populations yet to be discovered. Conclusions/Significance: We present a new method that is broadly applicable to studies of the dispersal of deep-sea organisms. This test case demonstrates the power and potential applications of our new method, in generating quantitative, testable hypotheses at multiple levels to solve the mismatch between observed and expected distributions: probabilistic predictions of locations of intermediate populations, potential alternative dispersal mechanisms, and expected population genetic structure. The global Argo data have never previously been used to address benthic biology, and our method can be applied to any non-swimming larvae of the deep-sea, giving information upon dispersal corridors and population densities in habitats that remain intrinsically difficult to assess.Irish Research Council for Science, Engineering and TechnologyScience Foundation Irelan

Emerging infectious disease implications of invasive mammalian species : the greater white-toothed shrew (Crocidura russula) is associated with a novel serovar of pathogenic Leptospira in Ireland

The greater white-toothed shrew (Crocidura russula) is an invasive mammalian species that was first recorded in Ireland in 2007. It currently occupies an area of approximately 7,600 km2 on the island. C. russula is normally distributed in Northern Africa and Western Europe, and was previously absent from the British Isles. Whilst invasive species can have dramatic and rapid impacts on faunal and floral communities, they may also be carriers of pathogens facilitating disease transmission in potentially naive populations. Pathogenic leptospires are endemic in Ireland and a significant cause of human and animal disease. From 18 trapped C. russula, 3 isolates of Leptospira were cultured. However, typing of these isolates by standard serological reference methods was negative, and suggested an, as yet, unidentified serovar. Sequence analysis of 16S ribosomal RNA and secY indicated that these novel isolates belong to Leptospira alstonii, a unique pathogenic species of which only 7 isolates have been described to date. Earlier isolations were limited geographically to China, Japan and Malaysia, and this leptospiral species had not previously been cultured from mammals. Restriction enzyme analysis (REA) further confirms the novelty of these strains since no similar patterns were observed with a reference database of leptospires. As with other pathogenic Leptospira species, these isolates contain lipL32 and do not grow in the presence of 8-azagunaine; however no evidence of disease was apparent after experimental infection of hamsters. These isolates are genetically related to L. alstonii but have a novel REA pattern; they represent a new serovar which we designate as serovar Room22. This study demonstrates that invasive mammalian species act as bridge vectors of novel zoonotic pathogens such as Leptospira

Invading and expanding : range dynamics and ecological consequences of the Greater White-Toothed Shrew (Crocidura russula) invasion in Ireland

Establishing how invasive species impact upon pre-existing species is a fundamental question in ecology and conservation biology. The greater white-toothed shrew (Crocidura russula) is an invasive species in Ireland that was first recorded in 2007 and which, according to initial data, may be limiting the abundance/distribution of the pygmy shrew (Sorex minutus), previously Ireland’s only shrew species. Because of these concerns, we undertook an intensive live-trapping survey (and used other data from live-trapping, sightings and bird of prey pellets/nest inspections collected between 2006 and 2013) to model the distribution and expansion of C. russula in Ireland and its impacts on Ireland’s small mammal community. The main distribution range of C. russula was found to be approximately 7,600 km2 in 2013, with established outlier populations suggesting that the species is dispersing with human assistance within the island. The species is expanding rapidly for a small mammal, with a radial expansion rate of 5.5 km/yr overall (2008–2013), and independent estimates from live-trapping in 2012–2013 showing rates of 2.4–14.1 km/yr, 0.5–7.1 km/yr and 0–5.6 km/yr depending on the landscape features present. S. minutus is negatively associated with C. russula. S. minutus is completely absent at sites where C. russula is established and is only present at sites at the edge of and beyond the invasion range of C. russula. The speed of this invasion and the homogenous nature of the Irish landscape may mean that S. minutus has not had sufficient time to adapt to the sudden appearance of C. russula. This may mean the continued decline/disappearance of S. minutus as C. russula spreads throughout the island

Meteorological factors associated with the timing and abundance of Hymenoscyphus fraxineus spore release

The ascomycete Hymenoscyphus fraxineus has spread across most of the host range of European ash with a high level of mortality, causing important economic, cultural and environmental effects. We present a novel method combining a Monte-Carlo approach with a generalised additive model that confirms the importance of meteorology to the magnitude and timing of H. fraxineus spore emissions. The variability in model selection and the relative degree to which our models are over- or under-fitting the data has been quantified. We find that both the daily magnitude and timing of spore emissions are affected by meteorology during and prior to the spore emission diurnal peak. We found the daily emission magnitude has the strongest associations to weekly average net radiation and leaf moisture before the emission, soil temperature during the day before emission and net radiation during the spore emission. The timing of the daily peak in spore emissions has the strongest associations to net radiation both during spore emission and in the day preceding the emission. The seasonal peak in spore emissions has a near-exponential increase/decrease, and the mean daily emission peak is approximately Gaussian.publishedVersio

Contrasting dispersal inference methods for the greater white-toothed shrew

International audienceA species' dispersal capability is difficult to quantify but important for a general understanding of a species' ecology and for applied conservation and management efforts. One approach is to use the information from individual genotypes to estimate recent dispersal rates. These genetic methods differ in the way they use the genotype data, their assumptions, and the information they give, but choosing one method over another is complicated by the lack of work that compares these methods on simulated or real data sets. We collected detailed, spatially resolved, individual data on the greater white-toothed shrew (Crocidura russula) in western Switzerland for which past studies have found an unusual female sex-biased dispersal. We analyzed the movement from 1 cohort of juvenile shrews with 7 published methods (i.e., mark-recapture, parentage analysis; genetic assignment; hierarchical F-statistics; and the programs BayesAss, IMIG, and STRUCTURE) and used a binomial test to make quantitative comparisons between the results of the methods. Our study indicates that the methods are broadly consistent, but parentage analysis appears the most powerful method for analyzing fine-scale dispersal patterns. In a conservation context, where the evaluation of long-term translocation success is critical for species management, the species studied and spatial scale considered will dictate which is the best suited method to estimate dispersal

The Fixation of Locally Beneficial Alleles in a Metapopulation

Extinction, recolonization, and local adaption are common in natural spatially structured populations. Understanding their effect upon genetic variation is important for systems such as genetically modified organism management or avoidance of drug resistance. Theoretical studies on the effect of extinction and recolonization upon genetic variance started appearing in the 1970s, but the role of local adaption still has no good theoretical basis. Here we develop a model of a haploid species in a metapopulation in which a locally adapted beneficial allele is introduced. We study the effect of different spatial patterns of local adaption, and different metapopulation dynamics, upon the fixation probability of the beneficial allele. Controlling for the average selection pressure, we find that a small area of positive selection can significantly increase the global probability of fixation. However, local adaption becomes less important as extinction rate increases. Deme extinction and recolonization have a spatial smoothing effect that effectively reduces spatial variation in fitness

Meteorological factors associated with the timing and abundance of Hymenoscyphus fraxineus spore release

The ascomycete Hymenoscyphus fraxineus has spread across most of the host range of European ash with a high level of mortality, causing important economic, cultural and environmental effects. We present a novel method combining a Monte-Carlo approach with a generalised additive model that confirms the importance of meteorology to the magnitude and timing of H. fraxineus spore emissions. The variability in model selection and the relative degree to which our models are over- or under-fitting the data has been quantified. We find that both the daily magnitude and timing of spore emissions are affected by meteorology during and prior to the spore emission diurnal peak. We found the daily emission magnitude has the strongest associations to weekly average net radiation and leaf moisture before the emission, soil temperature during the day before emission and net radiation during the spore emission. The timing of the daily peak in spore emissions has the strongest associations to net radiation both during spore emission and in the day preceding the emission. The seasonal peak in spore emissions has a near-exponential increase/decrease, and the mean daily emission peak is approximately Gaussian