Quantifying the effects of multiple processes on local abundance: a cohort approach for open populations |
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| Authors: | R.J. Schmitt,S.J. Holbrook,& C.W. Osenberg |
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| Affiliation: | Department of Ecology, Evolution and Marine Biology and the Coastal Research Center, Marine Science Institute, University of California, Santa Barbara, California 93106, USA.,;Department of Ecology, Evolution and Marine Biology and the Coastal Research Center, Marine Science Institute, University of California, Santa Barbara, California 93106, USA.,;Department of Zoology, University of Florida, Gainesville, Florida 32611–8525, USA. |
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| Abstract: | A challenge for species with demographically open populations is to evaluate the relative importance of various processes that together set local abundance. We developed a cohort-based framework for quantifying the influence of an external supply of colonists and subsequent density-independent and density-dependent mortality on local abundance. Two complementary approaches – based on limitation and elasticity – revealed the nature of interactions and nonlinearities among these processes. Data for an Indo-Pacific reef fish were used to document the settler–survivor relationship and to quantify natural variation in settlement. Limitation by density-dependence was two-fold and 20-fold greater than by supply or density-independent mortality, respectively. Elasticity analyses showed that adult abundance was 40% more sensitive to small proportionate changes in supply than in density-dependence. These techniques provide a way to compare across systems, which could enhance our ability to draw general conclusions regarding the processes that shape local abundance of species with open populations. |
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| Keywords: | Abundance density-dependence elasticity analyses recruitment limitation reef fish relative importance |
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