DOI: 10.5061/dryad.p1n86
title: Data from: Persistence of an extinction-prone predator-prey interaction through metapopulation dynamics

description: In theory, predator-prey pairs with extinction-prone local populations can
 persist through metapopulation dynamics, wherein local populations
 fluctuate asynchronously, occasionally providing dispersers that prevent
 permanent extinction in all patches. A few studies have shown that spatial
 structure can extend predator-prey persistence. However, no studies have
 unequivocally demonstrated the asynchrony among patches, low dispersal
 rates, and rescue effects that prove metapopulation dynamics extend
 persistence. We used a protist predator-prey pair to show that spatial
 subdivision lengthens persistence through metapopulation dynamics. The
 pair comprised the predaceous ciliate, Didinium nasutum, feeding on the
 bacterivorous ciliate, Colpidium cf. striatum. A replicated experiment
 assessed how habitat subdivision affects persistence. Undivided habitats
 were of four volumes: 30, 180, 270, and 750 mt. Subdivided microcosms, or
 ''arrays,'' were groups of nine or 25 linked 30-mL
 bottles (270 or 750 mt total volume). In arrays, predators and prey
 persisted for 130 d (602 prey and 437 predator generations), at which
 point the experiment ended. Predators went extinct in undivided microcosms
 of equivalent volumes within a mean of only 70 d. Predators persisted for
 a mean of just 19 d in isolated 30-mL bottles (equivalent to isolated
 patches of arrays). In a separate experiment, prey were driven extinct in
 four of 15 isolated 30-mL bottles, and persistence times of predators were
 broadly similar. We documented the following hallmarks of metapopulation
 dynamics: (1) asynchronous fluctuations in different subpopulations; (2)
 frequent local prey extinctions and recolonizations; (3) persistence of
 protists in arrays, despite extinction of isolated local populations; and
 (4) rescue effects in predator populations. Other experiments measured
 dispersal rates and the effects on local dynamics of immigrant predators
 and prey, and initial predator : prey ratios. Only a small fraction of
 protists dispersed within a generation, consistent with metapopulation
 dynamics. Immigration of predators increased the frequency of local
 extinctions of prey, and immigration of prey increased the persistence of
 both predators and prey. Higher initial predator:prey ratios decreased the
 persistence of prey in undivided volumes. Although the pair persisted
 regionally in arrays, data indicated that local extinctions of prey were
 common. In array patches, predator:prey ratios were higher and
 predator-prey cycles were shorter than in undivided volumes. Dispersal
 made local dynamics more prone to extinction, yet promoted regional
 persistence because the risk of extinction of distant subpopulations
 became independent.
description: Notes_for_data_archive_2014-11-05Text file (readme) giving a description of the data file fields.array_3x3_replicate_1Densities for an array as described in the readme file.array_3x3_replicate_2Densities for an array as described in the readme file.array_3x3_replicate_3Densities for an array as described in the readme file.array_5x5_replicate_1Densities for an array as described in the readme file.array_5x5_replicate_2Densities for an array as described in the readme file.array_5x5_replicate_3Densities for an array as described in the readme file.Undivided_volumes_270_750Densities for all replicates of 270 and 750 mL undivided volumes as described in the readme file.immigration_experiment_rawDensities for 30-mL bottles as described in the readme file. This includes both control 30-mL bottles in the spatial experiment and extra treatments used in the immigration experiment.