From the Inverse Density-Area Relationship to the Minimum Patch Size of a Host-Parasitoid System
The minimum amount of suitable habitat (MASH) is an important concept in conservation biological control. Two methods for estimating the MASH have been proposed by McCoy and Mushinsky based on an inverse density-area relationship. Using data of the population densities of aphid host-parasitoid-hyperparasitoid collected from wheat fields of different habitat sizes, we argued that the inverse density-area relationship may be an artifact. Significant correlations between population densities and patch sizes from all three trophic levels were found once the population density had been log-transformed. We could not obtain the same results if the population density had not been log-transformed. We estimated that the MASH for the aphid M. avena, S. graminum, A. avenae, A. gifuensis, P. aphidis, and Alloxysta sp. were 246, 246, 479, 495, 949, and 835 m 2 according to the methods of McCoy and Mushinsky. The scale-dependence and the systematic spatial variations of the host-parasitoid interaction suggests that we can achieve an optimal effect of biological control by manipulating the habitat patch sizes, although not based on the inverse density-area relationship. © 2011 The Ecological Society of Japan.