Suchergebnisse

Received: 1 July 2014 / Revised: 13 November 2014 / Accepted: 4 December 2014 / Published online: 11 December 2014 ; Recent research has shown that interactions between species with different functional traits can promote forest ecosystem processes. In the context of climate change, understanding whether species interactions in mixed-species ecosystems can improve the adaptation of these ecosystems to extreme climatic events is crucial to developing new management strategies. In this study, we investigated the impact of species interactions on the sap flux density of three Mediterranean tree species (Quercus faginea, Pinus nigra and Pinus sylvestris) during a summer drought. Measurements of foliar carbon isotopic composition (δ 13C) were also conducted on the same trees. The decline in transpiration during drought was the greatest for P. sylvestris and the least pronounced for Q. faginea. For P. nigra and Q. faginea, the decrease in transpiration as the drought progressed was lower when these species where interacting with another tree species, particularly with P. sylvestris. In contrast, the decrease for P. sylvestris was higher when this species was interacting with another species. Differing drought effects were consistent with the δ 13C values. We showed that the identity of the species present in the direct neighbourhood of a given tree can differentially influence water availability and water-use of these three co-existing Mediterranean tree species during a summer drought. Our findings suggest that species interactions play an important role in modulating the response of tree species to drought. Favouring tree species diversity in this region does not seem to be systematically beneficial in terms of soil water availability and water-use for all the interacting species. ; A.F. was supported by JAE-PREDOC from CSIC and co-funded by the European Union (Fondo Social Europeo). ; The research leading to these results was conducted within the FunDiv EUROPE project and has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant agreement No 265171. ; Peer reviewed

Modelling species interactions in diverse communities traditionally requires a prohibitively large number of species-interaction coefficients, especially when considering environmental dependence of parameters. We implemented Bayesian variable selection via sparsity-inducing priors on non-linear species abundance models to determine which species interactions should be retained and which can be represented as an average heterospecific interaction term, reducing the number of model parameters. We evaluated model performance using simulated communities, computing out-of-sample predictive accuracy and parameter recovery across different input sample sizes. We applied our method to a diverse empirical community, allowing us to disentangle the direct role of environmental gradients on species intrinsic growth rates from indirect effects via competitive interactions. We also identified a few neighbouring species from the diverse community that had non-generic interactions with our focal species. This sparse modelling approach facilitates exploration of species interactions in diverse communities while maintaining a manageable number of parameters. ; Funding Agencies|NSF EPSCoRNational Science Foundation (NSF)NSF - Office of the Director (OD) [EPS-2019528]; Australian Research CouncilAustralian Research Council [DP140100574]; VetenskapsradetSwedish Research Council [2017-05245]; European Social FundEuropean Social Fund (ESF) [RYC-2017-23666]; Ministerio de Economia y CompetitividadSpanish Government; Deutsches Zentrum fur integrative Biodiversitatsforschung Halle-Jena-Leipzig [FZT 118, 02548816]

Biodiversity data and databases are usually taxonomic specific (e.g. HerpNet, FishNet2, etc.), although there are cases of regional, non-taxa specific, biodiversity databases. And some biodiversity databases are inclined toward a functional category, such as invasive species. While it is critical to know of the existence and taxonomy of the many biological species of the world, a logical next step is to catalogue the linkages, or interactions, between and amongst the species. These types of data occur in an ecosystem context, culling a subset of many species from many taxa to form the species assemblages and communities and the resulting interactions between them that make up the species interaction network. Toward this end the Gulf of Mexico Species Interactions (GoMexSI) database, which is an application of GloBI, is endeavoring to assemble, extract, upload, and serve all of the recorded species interaction data for the Gulf of Mexico. To do this we are dependent on the interoperability of various biodiversity databases such as EOL (Encyclopedia of Life), NCBI (National Center for Biotechnology Information), WoRMS (World Register of Marine Species), etc to provide name resolution for detection of invalid species names. Using these data, GoMexSI takes advantage of the existing infrastructure of GloBI to integrate, link, and disseminate these data using various formats and methods. In addition, the relationship with GloBI negates the need to hire informatics staff, thus reducing costs. Data from GoMexSI is shared with scientists, and educators through GoMexSI's Wordpress based webpage. While GloBI is solely dependent on contributed datasets from scientists willing to share their data, GoMexSI expends a lot of effort harvesting species interaction data from published and unpublished resources, although contributed databases and datasets are accepted. The data extraction and editing process is very time consuming and costly. And funding sources for data extraction and editing are limited, making it difficult to maintain the effort. Much of the data in GoMexSI comes from theses and dissertations (25% of references), while other sources include peer reviewed literature, government technical reports, and conference proceedings. The GoMexSI project has focused on cataloguing predator/prey interactions of the Actinopterygii and Chondrichthyes, but recently began adding predator/prey interaction data on marine mammals, sea and shore birds, sea turtles, molluscs, and crustaceans to the database. Much time and effort has been devoted to developing standards for biodiversity data in order to record these data in a consistent way (i.e. Darwin Core). One of the key goals of the GoMexSI project from the outset has been to provide data standards for species interaction data where none existed previously. As we continue to work through the predator/prey interaction data of different taxa we are constantly confronted with new problems and issues in recording the data in a standard way. These include the description of predator and prey life history stages, description of prey parts, methods of length measurements, conversion of common names to scientific names, designation of locations, basis of prey identification, diet analysis methods, and others. Currently GoMexSI has 89,209 lines of data representing 2,146 unique interactor, gleaned from 172 references. Future plans for GoMexSI call for the addition of host/parasite, commensal, amensal, and mutualistic interaction data. In addition, we plan to include stable isotope data for Gulf species, as they serve as an integrated record of past interactions. We have shared our data collection methods and spreadsheets with the US Marine Mammal Commission in their effort to create a diet database for marine mammals. We are currently assisting Centro Interdisciplinario de Ciencias Marinas (CICIMAR) in La Paz Mexico to construct a species interaction database similar to GoMexSI for the Baja California (Gulf of California).

Based on graph theory studies this book seeks to understand how tropical species interact with each other and how these interactions are affected by perturbations in some of the most species-rich habitats on earth. Due to the great diversity of species and interactions in the tropics, this book addresses a wide range of current and future issues with empirical examples and complete revisions on different types of ecological networks: from mutualisms to antagonisms. The goal of this publication is not to be only for researchers but also for undergraduates in different areas of knowledge, and also to serve as a reference text for graduate-level courses mainly in the life sciences

Abstract
ContextAnthropogenic landscape modification and fragmentation result in loss of species and can alter ecosystem function. Assessment of the ecological value of urban reserve networks requires baseline and continued monitoring. However, depending on the desired indicators and parameters, effective monitoring can involve extensive sampling that is often financially or logistically infeasible.
AimsWe employed a low-intensity, mixed-detector survey design to monitor the small-mammal community across a network of 53 fragmented forest preserves (225 sites) in a highly urbanised landscape in the Chicago metropolitan area from August to October, 2009–2012.
MethodsWe used a sequential process to fit single-season occupancy and pairwise co-occurrence models for six common small mammal species to evaluate habitat associations and interspecific interactions.
Key resultsShrew species and meadow voles occurred more often in open canopy-associated habitats, whereas occupancy was greater for eastern chipmunks, grey squirrels and white-footed mice in closed-canopy habitats. Habitat associations were complicated by negative pairwise interactions, resulting in reduced occurrence of meadow voles when predatory short-tailed shrews were present and lower occupancy rates of white-footed mouse when chipmunk competitors where present. White-footed mice co-occurred with short-tailed shrews, but detection of white-footed mice was lower when either eastern chipmunks or short-tailed shrews were present, suggesting that densities of these species could be inversely related.
ConclusionsWe found evidence for both habitat segregation and interspecific interactions among small mammal species, by using low-intensity sampling across the reserve network. Thus, our sampling and analysis approach allowed for adequate assessment of the habitat associations and species interactions within a small-mammal community.
ImplicationsOur findings demonstrated the utility of this monitoring strategy and community as bioindicators for urban-reserve networks. The approach described holds promise for efficient monitoring of reserve networks in fragmented landscapes, critical as human population densities and urbanisation increase, and we discuss how adaptive sampling methods could be incorporated to further benefit conservation efforts.

In this paper, the interplay among four population species is offered. The system consists of two competitive prey, predator and super predators. The application of the hypothesis of the Sotomayor theorem for local bifurcation around every equilibrium point is adopted. It is detected that the transcritical bifurcation could occur near most of the system's equilibrium points, while saddle-node and pitchfork bifurcation can not be accrued at any of them. Further, the conditions that guarantee the accruing Hopf bifurcation are carried out. Finally, some numerical analysis is illustrated to confirm the analytical results.