Refuge Dynamics and Metapopulation Dynamics: An Experimental Test

Red scale, an insect pest of citrus, is under control by the parasitoid Aphytis melinus in many areas, and in our study area the interaction appears dynamically stable. The bark on the interior branches and trunk of trees provides a partial refuge for red scale, which are rarely attacked there by the parasitoid. In a grapefruit grove, we carried out a two-way experiment in which we manipulated the refuge population (present or removed) and either left trees connected with the rest of the grove or isolated individual trees with cages to test for metapopulation effects. The experiment ran for 17 mo, encompassing three generations of scale. Scale density in the exterior of refuge-removed trees decreased by about 60%. However, neither removal of the refuge population nor isolation of individual trees increased the temporal variability of the scale population in the exterior or led to drift in population density. Indeed, removal of the refuge population caused a decrease in temporal variability. We conclude that stability in the control population was not maintained by either refuge or metapopulation dynamics. Reduced scale recruitment and density in the exterior of trees lacking a refuge population were associated with increased (i.e., density-dependent) scale survival that did not reflect a change in parasitism.

[1]  Allan Stewart-Oaten,et al.  Estimation of Temporal Variability in Populations , 1995, The American Naturalist.

[2]  Ilkka Hanski,et al.  Metapopulation structure and migration in the butterfly Melitaea cinxia , 1994 .

[3]  L. Scott Mills,et al.  A Useful Role for Theory in Conservation , 1994 .

[4]  S. Walde.  Immigration and the dynamics of a predator-prey interaction in biological control , 1994 .

[5]  William W. Murdoch,et al.  POPULATION REGULATION IN THEORY AND PRACTICE , 1994 .

[6]  Andrew D. Taylor.  Population Variance and Stability: A Response to Horwood , 1993 .

[7]  J. Horwood.  Population Variance and Deterministic Stability Analysis , 1993 .

[8]  W. Wilson,et al.  Mobility versus density-limited predator-prey dynamics on different spatial scales , 1991, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[9]  Michael P. Hassell,et al.  Spatial structure and chaos in insect population dynamics , 1991, Nature.

[10]  R. Luck,et al.  Competition, resource partitioning and coexistence of an endoparasitoid Encarsia perniciosi and an ectoparasitoid Aphytis melinus of the California red scale , 1990 .

[11]  J. Daniel Hare,et al.  Variation in Life History Parameters of California Red Scale on Different Citrus Cultivars , 1990 .

[12]  W. Murdoch,et al.  A Refuge for Red Scale Under Control by Aphytis: Structural Aspects , 1989 .

[13]  William Gurney,et al.  Structured population models: a tool for linking effects at individual and population level , 1989 .

[14]  J. D. Reeve.  Environmental Variability, Migration, and Persistence in Host-Parasitoid Systems , 1988, The American Naturalist.

[15]  D. Yu,et al.  Temperature-Dependent Size and Development of California Red Scale (Homoptera: Diaspididae) and Its Effect on Host Availability for the Ectoparasitoid, Aphytis melinus DeBach (Hymenoptera: Aphelinidae) , 1988 .

[16]  W. W. Murdoch,et al.  Biological Control by the Parasitoid Aphytis melinus, and Population Stability of the California Red Scale , 1986 .

[17]  J. McNair,et al.  The effects of refuges on predator-prey interactions: a reconsideration. , 1986, Theoretical population biology.

[18]  Peter Chesson,et al.  Biological Control in Theory and Practice , 1985, The American Naturalist.

[19]  D. Moreno,et al.  Predictive Year-end California Red Scale (Homoptera: Diaspididae) Orange Fruit Infestations Based on Catches of Males in the San Joaquin Valley , 1985 .

[20]  John W. Tukey,et al.  Data Analysis and Regression: A Second Course in Statistics , 1977 .

[21]  W. Murdoch.  POPULATION REGULATION AND POPULATION INERTIA , 1970 .

[22]  Joseph H. Connell,et al.  A Predator‐Prey System in the Marine Intertidal Region. I. Balanus glandula and Several Predatory Species of Thais , 1970 .

[23]  V. Bailey,et al.  Interaction between hosts and parasites when some host individuals are more difficult to find than others , 1962 .

[24]  P. Debach,et al.  The Role of Weather and Entomophagous Species in the Natural Control of Insect Populations , 1958 .

[25]  A. Nicholson,et al.  The Balance of Animal Populations.—Part I. , 1935 .

[26]  William W. Murdoch,et al.  Regulation of an Insect Population Under Biological Control , 1995 .

[27]  S. Harrison,et al.  Local extinction in a metapopulation context: an empirical evaluation , 1991 .

[28]  Ilkka Hanski,et al.  Metapopulation dynamics : empirical and theoretical investigations , 1991 .

[29]  W. Murdoch,et al.  Predation and Population Stability , 1975 .

[30]  D. Rosen,et al.  Biological Control of Coccids by Introduced Natural Enemies , 1971 .

[31]  S. Fomin.  [Some mathematical problems of biology]. , 1970, Biofizika.