Phenotypic variation in egg survival in the predatory mite Phytoseiulus persimilis under dry conditions

In this study, we investigated the possibility to select for a strain of P. persimilis adapted to dry conditions. To understand the potential sources of phenotypic variation in egg survival under dry conditions, we tested the effects of genetic and environmental causes of variation in this trait. We compared egg hatching of five P. persimilis populations, under constant as well as variable humidity conditions, at 25°C. The results show no intraspecific genetic variation among the five tested populations in egg hatching under constant and variable humidity conditions. In all five populations, less than 20% of the eggs hatched when they were exposed to constant low (60% RH) humidity conditions. However, when eggs were exposed to successive cycles of low and high humidity, a common pattern observed in the field, significantly higher hatching rates were observed. Under variable humidity conditions, more than 73% of the eggs hatched successfully, even when exposure to high humidity was limited to only 13% of the egg developmental time. Although P. persimilis eggs suffered from a high rate of water loss under constant dry conditions, they were able to compensate for this water loss when exposed to high humidity conditions for a few hours during their development. A decreased biocontrol efficacy of P. persimilis under dry conditions may be explained by a higher egg mortality when relative humidity is constantly low. Yet, when relative humidity exhibits diurnal variations, periods o...
Source: Biological Control - Category: Biology Source Type: research