Results 261 to 270 of about 566,246 (303)

A Null Model of Morphospace Occupation

American Naturalist, 2005
Progress in understanding the relationship between lineage diversity, morphological diversity, and morphospace dynamics has been hampered by the lack of an appropriate null model of morphospace occupation. In this article, we introduce a simple class of models based on branching random walks (BRWs) for continuous traits.
Marcio R Pie, Joshua S Weitz
exaly   +4 more sources

THE SCHWINGER MODEL ON THE NULL-PLANE [PDF]

International Journal of Modern Physics E, 2007
We study the Schwinger Model on the null-plane using the Dirac method for constrained systems. The fermion field is analyzed using the natural null-plane projections coming from the γ-algebra and it is shown that the fermionic sector of the Schwinger Model has only second class constraints.
Casana, R., Pimentel, B. M., Zambrano, G. E. R.   +2 more
openaire   +3 more sources

Null Models for the Opportunity for Selection

The American Naturalist, 2022
Abstract Crow’s ‘Opportunity for Selection’ ( I =variance in relative fitness) is an important albeit controversial eco-evolutionary concept, particularly regarding the most appropriate null model(s).
Robin S, Waples, Thomas E, Reed
openaire   +2 more sources

The use and limitations of null-model-based hypothesis testing [PDF]

Biology and Philosophy, 2020
In this article I give a critical evaluation of the use and limitations of null-model-based hypothesis testing as a research strategy in the biological sciences.
Mingjun Zhang
exaly   +2 more sources

Null models in network neuroscience

Nature Reviews Neuroscience, 2022
Recent advances in imaging and tracing technology provide increasingly detailed reconstructions of brain connectomes. Concomitant analytic advances enable rigorous identification and quantification of functionally important features of brain network architecture.
František Váša, Bratislav Mišić
openaire   +2 more sources

Comments on Wilson's Null Model

Oecologia, 1987
We agree with several of Wilson's general observations concerning the difficulties and pitfalls of this approach to distributional ecology. We disagree on two of his main points, however. First, he has not correctly discussed our own procedure. Second, the model he has produced contains a serious flaw. Related to this second point, we find his analysis
M E, Gilpin, J M, Diamond
openaire   +2 more sources

Null models for null hypotheses in taxonomy: a test using Scyphozoa

Biological Journal of the Linnean Society, 2021
Abstract Although molecular tools are becoming more important in the delineation of scyphozoan species there is, perforce, a need to substantiate new species definitions using morphological data. Access to type material is often difficult and detailed, raw morphometric data are rarely provided in older type descriptions, which makes ...
Michael K Brown, Mark J Gibbons
openaire   +2 more sources

Null Models in Ecology

Annual Review of Ecology and Systematics, 1983
What determines the particular combinations of species found in biological communities, the number of those species, and their relative abundance? These questions are of perennial interest to ecologists, who often cite the influence of various factors-competition, predation, climate, nutrient availability, and chance dispersal events, to name a few ...
P H Harvey, R K Colwell, J W Silvertown, R M May   +3 more
openaire   +1 more source

A Note on Null Models: Justifying the Methodology

Ecology, 2002
The use of random, or null, models to determine whether species co-occurrences differ from chance expectations is an established technique in community ecology. Several methods have been used to draw conclusions regarding species co-occurrence patterns. We compared a sequential method derived previously with a recently proposed new method.
Bryan Manly, James G. Sanderson
openaire   +1 more source