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Requirements for the spatial storage effect are weakly evident for common species in natural annual plant assemblages
Author(s) -
Towers Isaac R.,
Bowler Catherine H.,
Mayfield Margaret M.,
Dwyer John M.
Publication year - 2020
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.3185
Subject(s) - abundance (ecology) , competition (biology) , intraspecific competition , ecology , storage effect , biology , ecosystem , fecundity , spatial ecology , vital rates , population , population growth , demography , sociology
Abstract Coexistence in spatially varying environments is theorized to be promoted by a variety of mechanisms including the spatial storage effect. The spatial storage effect promotes coexistence when (1) species have unique vital rate responses to their spatial environment and, when abundant, (2) experience stronger competition in the environmental patches where they perform better. In a naturally occurring southwest Western Australian annual plant system, we conducted a neighbor removal experiment involving eleven focal species growing in high‐abundance populations. Specifically, we measured species’ fecundity across a variety of environmental gradients in both the presence and absence of neighbors. For the environmental variables that we measured, there was only limited evidence for species‐specific responses to the environment, with a composite variable describing overstory cover and leaf litter cover being the best predictor of fecundity for a subset of focal species. In addition, although we found strong evidence for intraspecific competition, positive environment–competition covariance was only detected for one species. Thus, positive environment–competition covariance may not be as common as expected in populations of species growing at high abundance, at least when tested in natural assemblages. Our findings highlight the inherent limitations of using natural assemblages to study spatial coexistence mechanisms, and we urge empirical ecologists to take these limitations into account when designing future experiments.