A novel two-generation approach for understanding the population dynamics of gregarious parasitoids

Abstract

The population density of animals is generally measured as the number of individuals. Here, by using gregarious parasitoids as models, we show that this traditional approach omits one important parameter: the clutch size - body size - fertility correlation. Using this correlation, female gregarious parasitoids deliberately adjust the number of offspring laid in a host, determining not only the number of offspring but also the body sizes and reproductive potentials of those offspring. We propose a new two-generation approach for determining the population density of gregarious parasitoids. Using this new approach, which includes the clutch size - body size - fertility correlation, we show that the same fertility in the F1 generation can cause distinctly different fertility values in the F2 generation, and that, even with the same number of hosts, lower fertility in the F1 generation can cause higher fertility in the F2 generation. Our two-generation approach provides a new perspective for determining the individual fitness levels of gregarious parasitoids with new options for the modelling of parasitoid population dynamics.