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Abstract:
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Theoretical predictions suggest that adaptive phenotypic plasticity, and induced
defenses in particular, exert a stabilizing effect on ecological systems and increase
the likelihood of species coexistence. Nonetheless, up to now, there is little
empirical support for this hypothesized mechanism of diversity preservation.
We experimentally assessed the effects of induction of plastic morphological
responses triggered by a predator kairomone, on patterns of co-occurrence of two
herbivore populations of rotifers (Brachionus calyciflorus and B. havanaensis) sharing
resources (Chlorella vulgaris) and predators (Asplanchna brightwelli). To our knowledge,
this is the first experimental work conducted at the population level where noninduced
and induced states of same prey species are obtained through manipulating
the level of predator signal. Our objective was to assess the consequences of
induced defenses on the mean population density, population variability, evenness
and likelihood of persistence of competitor populations. Our results show that
induced defenses promote species coexistence through increasing the likelihood of
persistence and evenness of competing populations, over a gradient of resource
availability. |