Biology subjects

Rossberg, A. G.

Publications and source records attributed to Rossberg, A. G..

9 recordsLinked to original sources

bioRxiv2024

Isotope analysis of bird eye lens provides early-life information

Early-life environment has a long-lasting effect on later life, though its estimation is often prevented in the wild because of a lack of available methods. Recently, isotope analysis of eye lenses has attracted considerable interest as a means to reconstruct the environmental conditions experienced by animals during the developmental period. This analysis has mostly been confined to fish for practical reasons and remains to be resolved for application to other animals. In this study, we broadened its applicability by developing a novel approach and verifying its usability for the reconstruction of early-life environments. We performed a feeding experiment using Japanese quail (Coturnix japonica), in which we administered two diets: one composed mainly of C3 plants (low{delta} 13C and high{delta} 15N) and the other of C4 plants (high{delta} 13C and low{delta} 15N). Quails in the control group were continuously fed a C3-based diet from hatching until 200 days old, whereas those in the treatment groups (T10, T15, T20, and T40) were switched from the C3 to the C4-based diet at 10, 15, 20, and 40 days after hatching, respectively. We found that the{delta} 13C in the eye lenses of the treatment groups decreased from the center layer to the middle layer of the lens and then increased toward the outer layer, thus reflecting the diet change. In contrast, those of the control group exhibited a decreasing trend and equilibrated at the middle layer of the eye lens, with no increase thereafter. This novel approach revealed the postnatal feeding histories of the diet-shift experiment. The high{delta} 13C values observed in the center of the eye lenses would reflect the prenatal feeding environment, i.e., the C4-based diet consumed by their mothers, which is further reinforced by higher{delta} 15N values at this position due to the consumption of egg yolk-derived nutrition. These results indicate that the avian eye lens can be used as an "isotopic chronicle," which is a useful tool for reconstructing chronological isotopic information about their early-life history.

ecology↗

bioRxiv2024

Evaluating Biodiversity Credits Using Metacommunity Modelling

Global biodiversity enhancement is central to the UN Sustainable Development Goals and climate change mitigation. Achieving the Kunming-Montreal Global Biodiversity Frameworks 30 by 30 target requires an estimated additional US$700 billion annually. Biodiversity credit markets seek to address this funding gap by assigning financial value to biodiversity and ecosystem services. However, limited understanding of the metrics underpinning these credits pose significant barriers to their scalability and effectiveness. This pioneering study compares six credit metrics with six established biodiversity metrics to assess whether methodology choice influences metric responses to different ecosystem perturbations, identifying metrics best suited for specific interventions, and exploring comparability across metrics. A spatially explicit, multi-layered metacommunity simulation model, capable of reproducing a variety of empirically established macro-ecological patterns, was adapted to track ecosystem responses to six perturbation experiments and to record changes in the twelve tracked biodiversity metrics. Results reveal substantial divergence in how credit metrics assign value to nature, particularly between those estimating ecosystem services and those assessing species extinction risk. These findings underscore the need for careful alignment between metric selection and the ecological objectives of biodiversity projects and suggest that the development of a universal biodiversity credit is unlikely. Furthermore, in addition to metrics estimating ecosystem services, our results suggest that projects should incorporate metrics that are sensitive to declines in species-level abundances, thereby reflecting extinction risk.

ecology↗

bioRxiv2023

An efficient algorithm for Nash equilibria when harvesting interacting living resources

Natural ecological communities exhibit complex mixtures of interspecific biological interactions, which makes finding optimal yet sustainable exploitation rates challenging. Most fisheries management advice is at present based on applying the Maximum Sustainable Yield (MSY) target to each species in a community by modelling it as if it was a monoculture. Such application of single-species MSY policies to strongly interacting populations can result in tragic overexploitation. However, the idea of "maximising the yield from each species separately" can be extended to take into account species interactions using a multispecies or ecosystem model and determining a Nash Equilibrium (NE), where the yields of each species taken in isolation are simultaneously maximised. Here we present nash, an R package that streamlines the computation of NE reference points for fisheries and other systems represented by a user-defined multispecies or ecosystem model. We present two real-world fisheries management applications alongside performance benchmarks. Satisfactorily search results are shown across models with an approximate factor 15 increase in performance when compared to the expensive round-robbing sequential optimisation algorithms used by other authors in the literature. We believe that the nash package can play an instrumental role in fully implementing ecosystem-based management policies worldwide. Open Research statementThis submission uses novel code, which is provided, per our requirements, in an external repository to be evaluated during the peer review process via the following link https://github.com/ThomasDelSantoONeill/nash

ecology↗

bioRxiv2022

How temporal turnover in community composition is linked to anthropogenic pressure

Understanding the mechanisms behind biodiversity is central to assessing and forecasting anthropogenic impacts on ecological communities. However, quite how intrinsic ecological processes and external environmental drivers act together in natural systems to influence local temporal turnover is currently largely unexplored. Here, we determine how human impacts affect multiple metrics of bird community turnover to establish the ecological mechanisms behind compositional change. We used US Breeding Bird Survey data to calculate transect-level rates of three measures of temporal species turnover: a) short-term (initial rate of decline of Sorensen similarity), b) long-term (asymptotic Sorensen similarity), and c) overall species accumulation rate (species-time relationship exponents) over 2692 transects across 27 habitat types. We then hierarchically fit linear models to estimate the effect on these turnover metrics of anthropogenic impact via the Human Modification Index proxy, while accounting for observed species richness, the size of the species pool and annual environmental variability. We found broadly consistent impacts of increased anthropogenic pressures across diverse habitat types. The Human Modification Index was associated with greater turnover at long-timescales, but marginally slower short-term turnover. The species accumulation rate through time was not notably influenced. Examining anthropogenic impacts on different aspects of species turnover in combination allows greater ecological insight. Observed human impacts on short-term turnover were the opposite of existing expectations and suggest humans are disrupting the background turnover of these systems, rather than simply driving rapid directed turnover. The increased long-term turnover was driven by more frequent species changes between core and occasional status rather than greater arrival of new species. These results highlight the role of intrinsic dynamics and caution against simple interpretations of increased species turnover as reflections of environmental change. Open Research StatementNo new empirical data are used in the manuscript as all primary data is publicly available, as cited in the manuscript. Our code repository (including fitted model objects and markdown documents detailing all steps) is available at https://figshare.com/s/f5b9152ff7643efb347d.

ecology↗

bioRxiv2022

Codistribution as an indicator of whole metacommunity response to environmental change.

Metacommunity structure can be summarised by fitting joint species distribution models and partitioning the variance explained into environmental, spatial and codistribution components. Here we identify how these components respond through time with directed environmental change and propose this as an indicator of sustained directional pressure. Through simulations, we identify how declines in the codistribution component can diagnose ecological breakdown, while rises in environmental and spatial components may indicate losses in peripheral areas and dispersal limitations. We test the method in two well-studied systems. Butterflies are known to be strongly responding to climate change, and we show that over 21 years the codistribution component declines for butterfly communities in southern England. By contrast, birds in the same region are under less climate pressure and, despite high occupancy turnover, show minimal change in metacommunity structure. The approach has high potential to summarise and compare the impact of external drivers on whole communities.

ecology↗

bioRxiv2021

No pervasive size trend in global community dynamics.

While recent meta-analyses have suggested that local taxonomic richness has on average remained invariant, potential shifts in functional traits remain underexplored at global scales. Here, by linking the largest cross-taxa community time series database to multiple trait databases, we show that within communities there is no clear trend between size traits and changes in abundance rank over time. This suggests that there is no pervasive tendency across biomes for larger species to be doing proportionally better or worse than smaller species.

ecology↗

bioRxiv2021

Synthesising the multiple impacts of climatic variability on community responses to climate change

Recent developments in understanding and predicting species responses to climate change have emphasised the importance of both environmental variability and consideration of the wider biotic community. However, to date, the interaction between the two has received less attention. Both theoretical and empirical results suggest that the combined effect of environmental variability and interspecific interactions can have strong impacts on existing range limits. Here we explore how competitive interactions and temporal variability can interact with the potential to strongly influence range shift dynamics. We highlight the need to understand these between-process interactions in order to predict how species will respond to global change. In particular, future research will need to move from evaluating possibilities to quantifying their impact. We emphasise the value and utility of empirically parameterised models to determine the direction and relative importance of these forces in natural systems.

ecology↗

bioRxiv2020

Intrinsic ecological dynamics drive biodiversity turnover in model metacommunities

Turnover of species composition through time is frequently observed in ecosystems. It is often interpreted as indicating the impact of changes in the environment. Continuous turnover due solely to ecological dynamics--species interactions and dispersal--is also known to be theoretically possible, however the prevalence of such autonomous turnover in natural communities remains unclear. Here we demonstrate that observed patterns of compositional turnover and other important macroecological phenomena can be reproduced in large spatially explicit model ecosystems, without external forcing such as environmental change or the invasion of new species into the model. These results imply that the potential role of autonomous turnover as a widespread and important natural process is underappreciated, challenging assumptions implicit in many observation and management tools. Quantifying the baseline level of compositional change would greatly improve ecological status assessments. One Sentence SummaryBiodiversity change previously attributed to external drivers is explainable as resulting from intrinsic ecosystem dynamics.

ecology↗

bioRxiv2018

Metacommunity-scale biodiversity regulation and the self-organized emergence of macroecological patterns

There exist a number of key macroecological patterns whose ubiquity suggests the spatio-temporal structure of ecological communities is governed by some universal mechanisms. The nature of these mechanisms, however, remains poorly understood. Here we probe spatio-temporal patterns species richness and community composition using a simple metacommunity assembly model. Despite making no a priori assumptions regarding biotic spatial structure or the distribution of biomass across species, model metacommunities self-organize to reproduce well documented patterns including characteristic species abundance distributions, range size distributions and species area relations. Also in agreement with observations, species richness in our model attains an equilibrium despite continuous species turnover. Crucially, it is in the neighbourhood of the equilibrium that we observe the emergence of these key macroecological patterns. Biodiversity equilibria in models occur due to the onset of ecological structural instability, a population-dynamical mechanism. This strongly suggests a causal link between local community processes and macroecological phenomena.

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