About: Ecological network is a(n) research topic. Over the lifetime, 2029 publication(s) have been published within this topic receiving 86604 citation(s).
01 Feb 2005-Ecological Monographs
Abstract: Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.
01 Sep 1953-The American Naturalist
Abstract: In recent years the attention of experimental evolutionists has been increasingly directed toward polymorphism as furnishing desirable plasticity to a species. In particular, attention has been directed toward polymorphism with a known genetic basis. The best studied case is that of two alleles showing balanced polymorphismn: that is, the heterozygote has a higher adaptive value in a certain environment or range of environments than either homozygote. Such balanced polymorphism is the only way a pair of alleles can remain in equilibrium within a single environment (or ecological niche), if we ignore mutation pressure and migration from the outside. Onthe other hand, it would seem that the existence of several ecological niches, with one allele favored in one niche and the other allele favored in another, might increase the possibilities for attainment of equilibrium with both alleles present in substantial proportions. Recently the question arose of whether it was in fact possible to have equilibrium without the heterozygote being superior to both homozygotes in any single niche. It is shown below that under certain assumptions the answer is yes. The model here proposed is as follows: Let there be alleles A and A' with gene frequencies of q and 1 q respectively, and let mating be at random over the whole population, so that the initial zygotic frequencies are q2AA, 2q(1 -q)AA'j and (1 q)2AA'. After fertilization the zygotes settle down at random in large numbers into each of the niches, and are thereafter immobile. There is then differential mortality ending with a fixed number of individuals in each niche. After selection the relative frequencies of AA, AA', and A'A'will be Wjq2:2q(1 ~-q):Vj(1 -q)3 in niche 1, W2q2:2q(1-q):V2(1 -q)a in the second niche, etc., where W1l and V1 are the adaptive values of AA and A'A'individuals relative to AA'in the i-th niche. We need consider only intra-niche comparisons and not the absolute viabilities in the different niches. If we disregard drift and consider only the force of selection, the absolute number of survivors in the different niches is also irrelevant and we may work with the numbers cl, where ci is the proportion of the total survivors to be found in the i-th niche, and =ci = 1. To complete the model, we suppose that at the time of reproduction the survivors leave the niches, and that mating is at random in the entire population. If we denote by q'the frequency of A in this mating popu-
Topics: Ecological niche (74%), Environmental niche modelling (69%), Niche segregation (68%) ...read more
Abstract: In natural communities, species and their interactions are often organized as nonrandom networks, showing distinct and repeated complex patterns. A prevalent, but poorly explored pattern is ecological modularity, with weakly interlinked subsets of species (modules), which, however, internally consist of strongly connected species. The importance of modularity has been discussed for a long time, but no consensus on its prevalence in ecological networks has yet been reached. Progress is hampered by inadequate methods and a lack of large datasets. We analyzed 51 pollination networks including almost 10,000 species and 20,000 links and tested for modularity by using a recently developed simulated annealing algorithm. All networks with >150 plant and pollinator species were modular, whereas networks with <50 species were never modular. Both module number and size increased with species number. Each module includes one or a few species groups with convergent trait sets that may be considered as coevolutionary units. Species played different roles with respect to modularity. However, only 15% of all species were structurally important to their network. They were either hubs (i.e., highly linked species within their own module), connectors linking different modules, or both. If these key species go extinct, modules and networks may break apart and initiate cascades of extinction. Thus, species serving as hubs and connectors should receive high conservation priorities.
13 Aug 2010-Science
Abstract: Research on the relationship between the architecture of ecological networks and community stability has mainly focused on one type of interaction at a time, making difficult any comparison between different network types. We used a theoretical approach to show that the network architecture favoring stability fundamentally differs between trophic and mutualistic networks. A highly connected and nested architecture promotes community stability in mutualistic networks, whereas the stability of trophic networks is enhanced in compartmented and weakly connected architectures. These theoretical predictions are supported by a meta-analysis on the architecture of a large series of real pollination (mutualistic) and herbivory (trophic) networks. We conclude that strong variations in the stability of architectural patterns constrain ecological networks toward different architectures, depending on the type of interaction.
Topics: Ecological network (59%)
01 Feb 2013-Biological Reviews
Abstract: Predicting which species will occur together in the future, and where, remains one of the greatest challenges in ecology, and requires a sound understanding of how the abiotic and biotic environments interact with dispersal processes and history across scales. Biotic interactions and their dynamics influence species' relationships to climate, and this also has important implications for predicting future distributions of species. It is already well accepted that biotic interactions shape species' spatial distributions at local spatial extents, but the role of these interactions beyond local extents (e.g. 10 km2 to global extents) are usually dismissed as unimportant. In this review we consolidate evidence for how biotic interactions shape species distributions beyond local extents and review methods for integrating biotic interactions into species distribution modelling tools. Drawing upon evidence from contemporary and palaeoecological studies of individual species ranges, functional groups, and species richness patterns, we show that biotic interactions have clearly left their mark on species distributions and realised assemblages of species across all spatial extents. We demonstrate this with examples from within and across trophic groups. A range of species distribution modelling tools is available to quantify species environmental relationships and predict species occurrence, such as: (i) integrating pairwise dependencies, (ii) using integrative predictors, and (iii) hybridising species distribution models (SDMs) with dynamic models. These methods have typically only been applied to interacting pairs of species at a single time, require a priori ecological knowledge about which species interact, and due to data paucity must assume that biotic interactions are constant in space and time. To better inform the future development of these models across spatial scales, we call for accelerated collection of spatially and temporally explicit species data. Ideally, these data should be sampled to reflect variation in the underlying environment across large spatial extents, and at fine spatial resolution. Simplified ecosystems where there are relatively few interacting species and sometimes a wealth of existing ecosystem monitoring data (e.g. arctic, alpine or island habitats) offer settings where the development of modelling tools that account for biotic interactions may be less difficult than elsewhere.