Evol Ecol Res 3: 759-766 (2001)     Full PDF if your library subscribes.

Local extinctions promote co-existence of semelparous and iteroparous life histories

Esa Ranta,1* David Tesar1 and Veijo Kaitala1,2

1Integrative Ecology Unit, Division of Population Biology, Department of Ecology and Systematics, University of Helsinki, PO Box 17, FIN-00014 Helsinki and 2Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, FIN-40351 Jyväskylä, Finland

Author to whom all correspondence should be addressed.
e-mail: esa.ranta@helsinki.fi


We studied the evolution of semelparity (reproducing once per lifetime) and iteroparity (reproducing repeated times in subsequent breeding seasons) using numerical simulations. In particular, we were interested in the conditions enabling long-term persistence of the two strategies in a given population system. Our general approach was to simulate a semelparous and an iteroparous population in a spatially structured system where dispersing individuals link habitable sub-units together. The local dynamics of each sub-unit was subjected to demographic stochasticity. It appears that demographic stochasticity and local extinction processes may enhance the long-term co-existence of semelparity and iteroparity. The key for co-existence of the two life histories is as follows. First, the population is set into a spatially structured context. Second, demographic stochasticity prevents local population dynamics reaching steady-state equilibria and creates strategy-specific local extinctions. These vacancies will be occupied by dispersing individuals of semelparous and iteroparous life histories. Without the joint action of these elements, the co-existence of the two life histories would become impossible.

Keywords: co-existence, Cole’s paradox, iteroparity, life history, semelparity, stochasticity.

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