Dissertation
Partitioning abiotic and biotic contributions to community variation
Doctor of Philosophy (Ph.D.), Drexel University
Dec 2013
DOI:
https://doi.org/10.17918/etd-4366
Abstract
It is well known that both environmental factors and species interactions structure ecological com- munities. To study community composition responses to environmental gradients, ordination and regression techniques are typically employed; however, for studying species interactions, methods primarily rely on analyzing patterns of presence/absence. Each of these types of analyses are carried out independently because there is a lack of unified statistical methods for simultaneous analysis of biotic and abiotic factors influencing community composition. This thesis presents a unified method that enables the removal of environmentally explained variation from species responses so that ap- parent species interactions are not masked or augmented by the abiotic responses, thus partitioning the abiotic/biotic factors. To achieve a unified method, first, species responses to environmental gradients are removed via a multivariate regression procedure. Second, the residual responses, void of environmentally explained variation, are tested for species interactions using a null model. Third, communities identified with significant interactions are summarized by the average pairwise covariation among the member species. The method can be used to test hypotheses about species interactions when environmental gradients are present and it may be used to calculate percentages of variation explained due to abiotic, biotic and unexplained factors. Via a sensitivity analysis, I demonstrate that sufficient detection (95%) and false positive rates (5%) can be achieved under particular site-species ratios, number of environmental gradients, and covariation-to-noise ratios. My method can guarantee a sufficient average false positive rate (5%) for communities with > 60 samples, up to 500 species and influenced by up to 4 environmental gradients.
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Details
- Title
- Partitioning abiotic and biotic contributions to community variation
- Creators
- Steven Daniel Essinger - DU
- Contributors
- Gail L. Rosen (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Electrical (and Computer) Engineering (1970-2026); Drexel University
- Other Identifier
- 4366; 991014632051404721