[Minimum amounts of suitable habitat for wheat aphid, parasitoid, and hyperparasitoid in facility-based agricultural landscapes].

Minimum amount of suitable habitat (MASH) is the minimum habitat area that a population requires to persist in a given environmental setting for a long time,being an important aspect of population viability analysis (PVA). In this paper,we estimated the MASH for wheat aphids,parasitoids,and hyperparasitoids in facility-based agricultural landscapes in Yinchuan Plain of Northwest China,based on the relationships between population density and habitat area,and by using regression analysis. It was found that the population density and growth rate were consistently inversely related to area,but the exact mathematical functions varied with different species,especially those at different trophic levels. The MASH values for Macrosiphum avenae,Schizaphis graminum,Aphidius avenae,Aphidius gifuensis,and Pachyneuron aphidis were estimated with a polynormal regression model of density-area relationship,and the results were similar to those estimated from an inverse relationship between population and area. The differences of MASH between trophic levels were significant. It was concluded that these species had different values of MASH,which reflected their different habitat requirements and their differences in body size,migration,trophic position,and habitat quality. For parasitoids,the highest parasitic rates always took place at a spatial scale of 800-1000 m2,which could be considered as the base of aphids control with parasitoids,while the difference of MASH among trophic levels could be used to suppress the pest population.