Facultative production of multiple-egg clutches in a quasi-gregarious parasitoid: fitness gains for offspring at low developmental temperature

Abstract

In the quasi-gregarious parasitoid wasp Anastatus disparis, a mother may lay more than one egg in a host during a single host encounter. This is conventionally known as self-superparasitism and, since only one adult offspring can complete development on the host, it may represent a waste of eggs and time. However, this behavior may be better described as “multiple-egg clutches,” which differs fundamentally from self-superparasitism and has seldom been addressed. The potential benefits of laying multiple-egg clutches are currently unclear, and we therefore aimed to investigate them in A. disparis. First, our results showed that production of multiple-egg clutches by A. disparis is not due to a lack of discrimination between unparasitized and parasitized hosts, as females preferred to lay eggs in unparasitized hosts. It was also unrelated to the age of the female or her mating status, or to the presence of conspecific females. However, compared to the temperatures of 26 and 32 °C, we observed that the frequency of multiple-egg clutches increased at the temperature of 20 °C. In addition, low developmental temperatures significantly decreased the rate of successful wasp eclosion from hosts in which a single egg was deposited, and this rate was increased by laying multiple-egg clutches. These results suggest that female A. disparis adults produce multiple-egg clutches to increase the probability of obtaining offspring from the host, and may have the ability to regulate oviposition and reproduction strategy based on environmental temperature. Anastatus disparis exhibited an oviposition behavior of facultative production of multiple-egg clutches, which is not due to a lack of host discrimination, or due to the age of the female or her mating status nor the presence of conspecific females. However, our results suggest that A. disparis adults produce multiple-egg clutches when it increased the probability of obtaining offspring from the host, and may have the ability to regulate their oviposition strategy based on environmental temperature.