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Quantifying the effects of multiple processes on local abundance: a cohort approach for open populations
Author(s) -
Schmitt R.J.,
Holbrook S.J.,
Osenberg C.W.
Publication year - 1999
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1046/j.1461-0248.1999.00086.x
Subject(s) - abundance (ecology) , density dependence , ecology , relative species abundance , biology , population density , reef , elasticity (physics) , population , demography , physics , sociology , thermodynamics
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.