Ontogenetic specialism in predators with multiple niche shifts prevents predator population recovery and establishment

The effects of ontogenetic niche shifts on community structure and dynamics are underexplored, despite the occurrence of such shifts in the majority of animal species. We studied the form of niche shifts in a predator that exhibits multiple ontogenetic niche shifts, and analyzed how this life histor...

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Bibliographic Details
Published in:	Ecology (Durham) 2014-09, Vol.95 (9), p.2409-2422
Main Authors:	van Leeuwen, A., Huss, M., Gårdmark, A., de Roos, A. M.
Format:	Article
Language:	eng
Subjects:	alternative stable community states animals Community ecology community structure complex life cycle density dependent growth Diet diet shift Ecological life histories Ecology Ekologi Equilibrium Extinction food availability invasion life history Marine ecology Morphogenesis Natural resources ontogenetic niche shift ontogeny piscivores piscivory Population density Population dynamics Population ecology Population growth Predation predator extinction predator-prey dynamics Predators Productivity size-structure mismatch
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Summary:	The effects of ontogenetic niche shifts on community structure and dynamics are underexplored, despite the occurrence of such shifts in the majority of animal species. We studied the form of niche shifts in a predator that exhibits multiple ontogenetic niche shifts, and analyzed how this life history complexity affects the size-structured predator-prey dynamics in the system. The predator represents either an ontogenetic generalist, exhibiting a partial shift to predation (in which case an alternative resource is also available) or an ontogenetic specialist, exhibiting a complete shift (in which case the predator depends entirely on predation). We showed two effects on community dynamics from accounting for a complete niche shift to predation: (1) occurrence of alternative stable community states (coexistence and a prey-only community state) and (2) occurrence of deterministic extinction following initially successful invasion (predators can invade an equilibrium with only prey, but are bound to go extinct after a few generations). Both phenomena are due to the match or mismatch in the timing of predators and suitably sized prey and the growth trajectory of the predator, which is plastic, due to the population feedback on available resources. In the case of persistence without invasion (alternative stable community states), slow growth during the pre-piscivorous life stage is necessary to stay in tune with the prey cycle; in the case of extinction following invasion, slow growth through the pre-piscivorous life stage causes the predator to reach the completely piscivorous stage when there is no prey available to feed upon. Somatic growth rates are directly coupled to food availability, which, in turn, is the result of density-dependent feedbacks in the system. Since they primarily determine these density-dependent feedbacks, the ontogenetic niche shifts in predator life history structure the community to a major extent.
ISSN:	0012-9658 1939-9170 1939-9170