Browsing by Author "Corcoran, Derek"

Now showing 1 - 6 of 6
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    A Comparison of the Maximum Entropy Principle Across Biological Spatial Scales
    (2019) Cofre, Rodrigo; Herzog, Ruben; Corcoran, Derek; Rosas, Fernando E.
    Despite their differences, biological systems at different spatial scales tend to exhibit common organizational patterns. Unfortunately, these commonalities are often hard to grasp due to the highly specialized nature of modern science and the parcelled terminology employed by various scientific sub-disciplines. To explore these common organizational features, this paper provides a comparative study of diverse applications of the maximum entropy principle, which has found many uses at different biological spatial scales ranging from amino acids up to societies. By presenting these studies under a common approach and language, this paper aims to establish a unified view over these seemingly highly heterogeneous scenarios.
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    Alteration of coastal productivity and artisanal fisheries interact to affect a marine food web
    (2021) Isidora Avila-Thieme, M.; Corcoran, Derek; Perez-Matus, Alejandro; Wieters, Evie A.; Navarrete, Sergio A.; Marquet, Pablo A.; Valdovinos, Fernanda S.
    Top-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a top-down force can shorten and destabilize food webs, while effects driven by climate change can alter the bottom-up forces of primary productivity. We assessed the response of a highly-resolved intertidal food web to these two global change drivers, using network analysis and bioenergetic modelling. We quantified the relative importance of artisanal fisheries as another predator species, and evaluated the independent and combined effects of fisheries and changes in plankton productivity on food web dynamics. The food web was robust to the loss of all harvested species but sensitive to the decline in plankton productivity. Interestingly, fisheries dampened the negative impacts of decreasing plankton productivity on non-harvested species by reducing the predation pressure of harvested consumers on non-harvested resources, and reducing the interspecific competition between harvested and non-harvested basal species. In contrast, the decline in plankton productivity increased the sensitivity of harvested species to fishing by reducing the total productivity of the food web. Our results show that strategies for new scenarios caused by climate change are needed to protect marine ecosystems and the wellbeing of local communities dependent on their resources.
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    Bird Communities in Coastal Areas. Effects of Anthropogenic Influences and Distance From the Coast
    (2022) Graells, Giorgia; Celis-Diez, Juan L.; Corcoran, Derek; Gelcich, Stefan
    Urbanization effects have been studied all over the world, documenting impact in species richness, abundances and changes in species communities. Birds have been broadly used as study models. In general, urbanization affects birds, reducing species richness, especially in the urban core, and increasing species richness in areas with intermediate levels of disturbance, such as suburbs. Urbanization also changes species assemblages depending on urban characteristics and resources available, creating habitats for different species. Even when more than half of the cities in the world are on the coast, the effects of urbanization on habitat use of terrestrial and marine birds in coastal urban environments has received little attention. We hypothesized that coastal cities would present different bird diversity in modified marine areas and modified inland areas as terrestrial and marine ecosystems coexist. We predict that modified marine areas will have higher species richness than modified inland areas and natural marine areas. For bird assemblages, we expect to find similar species compositions between sites with similar habitat characteristics more than closeness. We compare habitat use of marine and terrestrial avifauna in the human-modified coastal city of Valparaiso, Chile, characterized by a range of urban developments within city boundaries. We specifically compare corrected bird abundance in six different possible habitats for birds, according to distance to the coast, and human influence. Bird counts (50 m fixed radius) were conducted in winter and spring of 2019. Bird species richness and abundances, corrected by the probability of detection, were estimated. Additionally, species composition and occupancy of bird species in those habitats were calculated. Results show that coastal urban cities can provide different habitats for bird species. Modified inland habitats differ from semi-natural inland habitats and from the modified beaches in species richness and species composition. Environmental heterogeneity in coastal cities seems to allow the coexistence of marine and terrestrial bird species, showing differences in species richness and bird assemblages for marine-inland environments and natural- modified habitats. Results highlight the need to consider these factors for urban planning in order to conserve bird diversity in coastal urban areas.
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    Extent, configuration and diversity of burned and forested areas predict bat richness in a fire-maintained forest
    (2021) Blakey, Rachel V.; Webb, Elisabeth B.; Kesler, Dylan C.; Siegel, Rodney B.; Corcoran, Derek; Cole, Jerry S.; Johnson, Matthew
    Context Fire transforms, fragments and sometimes maintains forests, creating mosaics of burned and unburned patches. Highly mobile animals respond to resources in the landscape at a variety of spatial scales, yet we know little about their landscape-scale relationships with fire. Objectives We aimed to identify drivers of bat richness in a landscape mosaic of forested and burned areas while identifying spatial scales at which bat richness was most strongly related to extent, configuration, and diversity measures of landscape-level habitat. Methods We used multi-species hierarchical occupancy modelling to relate bat richness to landscape variables at 10 spatial scales, based on acoustic data collected in the Sierra Nevada, United States. We also assessed redundancy among landscape variable type (extent, configuration, and diversity) and between focal patch types (forested and burned). Results Bat richness was positively associated with heterogenous landscapes, shown by positive associations with pyrodiversity, extent and mean area of burned patches, burned and forested edge density and patch density and relationships were generally consistent across scales. Extent of forest cover and burned areas were highly correlated, but configuration and diversity of these patch types diverged. Conclusions Bat communities of our study area appear to be largely resilient to wildfire and adapted to more heterogenous forests and shorter-interval fire regimes that likely predominated before the fire suppression era.
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    NetworkExtinction: An R package to simulate extinction propagation and rewiring potential in ecological networks
    (2023) Ávila Thieme, María Isidora; Kusch, Erik; Corcoran, Derek; Castillo, Simón P.; Valdovinos, Fernanda S.; Navarrete C., Sergio; Marquet, P. A.
    Earth's biosphere is undergoing drastic reorganization due to the sixth mass extinction brought on by the Anthropocene. Impacts of local and regional extirpation of species have been demonstrated to propagate through the complex interaction networks they are part of, leading to secondary extinctions and exacerbating biodiversity loss. Contemporary ecological theory has developed several measures to analyse the structure and robustness of ecological networks under biodiversity loss. However, a toolbox for directly simulating and quantifying extinction cascades and creating novel interactions (i.e. rewiring) remains absent. Here, we present NetworkExtinction—a novel R package which we have developed to explore the propagation of species extinction sequences through ecological networks and quantify the effects of rewiring potential in response to primary species extinctions. With NetworkExtinction, we integrate ecological theory and computational simulations to develop functionality with which users may analyse and visualize the structure and robustness of ecological networks. The core functions introduced with NetworkExtinction focus on simulations of sequential primary extinctions and associated secondary extinctions, allowing user-specified secondary extinction thresholds and realization of rewiring potential. With the package NetworkExtinction, users can estimate the robustness of ecological networks after performing species extinction routines based on several algorithms. Moreover, users can compare the number of simulated secondary extinctions against a null model of random extinctions. In-built visualizations enable graphing topological indices calculated by the deletion sequence functions after each simulation step. Finally, the user can estimate the network's degree distribution by fitting different common distributions. Here, we illustrate the use of the package and its outputs by analysing a Chilean coastal marine food web. NetworkExtinction is a compact and easy-to-use R package with which users can quantify changes in ecological network structure in response to different patterns of species loss, thresholds and rewiring potential. Therefore, this package is particularly useful for evaluating ecosystem responses to anthropogenic and environmental perturbations that produce nonrandom and sometimes targeted, species extinctions.
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    Reconstructing ecological networks with noisy dynamics
    (ROYAL SOC, 2020) Freilich, Mara A.; Rebolledo, Rolando; Corcoran, Derek; Marquet, Pablo A.
    Ecosystems functioning is based on an intricate web of interactions among living entities. Most of these interactions are difficult to observe, especially when the diversity of interacting entities is large and they are of small size and abundance. To sidestep this limitation, it has become common to infer the network structure of ecosystems from time series of species abundance, but it is not clear how well can networks be reconstructed, especially in the presence of stochasticity that propagates through ecological networks. We evaluate the effects of intrinsic noise and network topology on the performance of different methods of inferring network structure from time-series data. Analysis of seven different four-species motifs using a stochastic model demonstrates that star-shaped motifs are differentially detected by these methods while rings are differentially constructed. The ability to reconstruct the network is unaffected by the magnitude of stochasticity in the population dynamics. Instead, interaction between the stochastic and deterministic parts of the system determines the path that the whole system takes to equilibrium and shapes the species covariance. We highlight the effects of long transients on the path to equilibrium and suggest a path forward for developing more ecologically sound statistical techniques.