Pattern of species occurrence in detritus-based communities with variable connectivity (original) (raw)
Deterministic processes vary during community assembly for ecologically dissimilar taxa
Nature communications, 2015
The continuum hypothesis states that both deterministic and stochastic processes contribute to the assembly of ecological communities. However, the contextual dependency of these processes remains an open question that imposes strong limitations on predictions of community responses to environmental change. Here we measure community and habitat turnover across multiple vertical soil horizons at 183 sites across Scotland for bacteria and fungi, both dominant and functionally vital components of all soils but which differ substantially in their growth habit and dispersal capability. We find that habitat turnover is the primary driver of bacterial community turnover in general, although its importance decreases with increasing isolation and disturbance. Fungal communities, however, exhibit a highly stochastic assembly process, both neutral and non-neutral in nature, largely independent of disturbance. These findings suggest that increased focus on dispersal limitation and biotic intera...
Journal of Sea Research, 2014
In ecology understanding variation in connectivity is central for how biodiversity is maintained. Field studies on dispersal and temporal dynamics in community regulating processes are, however, rare. We test the short-term temporal stability in community composition in a soft-sediment benthic community by determining among-sampling interval similarity in community composition. We relate stability to in situ measures of connectivity (wind, wave, current energy) and rates of dispersal (quantified in different trap types). Waves were an important predictor of when local community taxa are most likely to disperse in different trap-types, suggesting that wave energy is important for connectivity in a region.
Dispersal and persistence: Population processes and community dynamics
Folia Geobotanica, 2000
If we look at plant cover at a certain site, we can observe that it is made up of a number of species of different size and form, conferring a certain structure to the vegetation cover. If we compare two sites, we invariably see differences in structure and species composition. These differences are repeated across a hierarchy of scales: at the local scale, the regional scale and ultimately at the continental scale. By comparing structure and species compositions across a larger number of sites, a statistical pattern emerges from the data: some species are found together more frequently than expected and others seem to avoid each other. In fact, these positive and negative associations result in the observation that the species composition of a site is not just a random collection of species but is patterned, resulting in recognizable plant communities.
Community dynamics are governed by two opposed processes: species sorting, which produces deterministic dynamics leading to an equilibrium state, and ecological drift, which produces stochastic dynamics. Despite a great deal of theoretical and empirical work aiming to demonstrate the predominance of one or the other of these processes, the importance of drift in structuring communities and maintaining species diversity remains contested. Here we present the results of a basic community dynamics experiment using floating aquatic plants, designed to measure the relative contributions of species sorting, ecological drift to community change over about a dozen generations. We found that species sorting became overwhelmingly dominant as the experiment progressed, and directed communities towards a stable equilibrium state maintained by negative frequency-dependent selection. The dynamics of any particular species depended on how far its initial frequency was from its equilibrium frequenc...
The role of stochastic processes in producing nested patterns of species distributions
Oikos, 2006
The role of stochastic processes in producing nested patterns of species distributions. Á Oikos 114: 159 Á167. Nestedness has received considerable attention in community ecology and conservation biology from both theoretical and empirical perspectives. This has lead to the creation of various metrics and null models to analyze nested subsets, all of which rely on the random placement of species to assess significance. However, if immigration and extinction are the processes that underlie species distributions on island systems, then null models might be better determined on the basis of randomly placed individuals. Consequently, we examined the effects of species Áabundance distributions (uniform, dominance Ádecay, random Áassortment, and dominance Ápreemption), island Ásize distributions (uniform and linear decrease), and total abundances (128, 256, 512, 1024, 2048, 4096 and 8192) on the degree of nestedness and its significance. Generally, matrices of species presence and absence created from the random placement of individuals were nested significantly according to null models based on the random placement of species. Island size and abundance had less of an effect on nestedness in systems dominated by only a few species than in systems in which abundances were distributed more evenly. Stochastic processes, such as the random placement of individuals, predispose systems to evince patterns of nestedness at the species level, which may account, in part, for the ubiquity of nestedness in nature.
The Co-Distribution of Species in Relation to the Neutral Theory of Community Ecology
Ecology, 2005
Patterns of species co-distribution have often been used to infer the operation of processes such as competition and selection among species. Ecological specialization should create unexpectedly strong species associations, reflected by high positive or negative correlations between species that are adapted to similar or different kinds of site.
Local versus regional processes and the control of community structure
Community Ecology, 2016
The contribution of local (e.g., competition) and regional (e.g., dispersal) processes in the structure of communities remains an unresolved issue. In general, a tendency to assume local processes to be deterministic and regional to be stochastic dominates, although it is challenged. Fortunately, it can be cast as a testable proposition: if correct, the degree of determinism in the final community structure might indicate which process is more prominent in the control of community structure. However, recent findings have also suggested that stochastic patterns can arise from local processes and that dispersal can homogenize communities, which would make them appear deterministic irrespective of the mechanism involved. To evaluate these compet� ing expectations we conducted an experiment where the initial communities had the same composition and species abundances. We hypothesized that if local processes dominate, then arrays of communities will show divergence of community structures whether connected by dispersal or not (i.e., being fully isolated). Alternatively, if regional processes dominate, the dispersal connected communities should converge while isolated ones should not. We found, however, that both groups of experimental communities showed similar patterns of change � a decline in similarity and a tendency to diverge. This suggests that biological interactions, demographic stochasticity, or both, exert noticeable control over community structure such that they reduce simi� larity among replicate communities and diversify their final states. We speculate that these mechanisms enhance potential for species additions, particularly in conjunction with factors such as dispersal and the size of the regional species pool.