Unmasking acquisition and allocation variance through environment manipulation

Abstract

To understand how selection affects a population, finding out more about the acquisitional and allocational components of the genetic diversity within it is essential. Studying trade-offs between life-history traits in different environments can reveal differences in the degree of acquisitional and allocational genetic variance within a population. Learning about how selection acts can give us an insight into how adaptation evolves, which is important regarding resistance development against pesticides. My thesis aims to use Helicoverpa armigera moth larvae to quantify the genetic effects of life-history trait trade-offs in different environments to analyze acquisition and allocation patterns within a population. The life-history traits measured was pupal mass, pupal development rate and survival. To manipulate the environment, two different larval diets were used, one rich and one poor, as well as different doses of the microbial biopesticide Bacillus thuringiensis. A half-sibling design was conducted to quantify genetic correlations between the life-history traits. The biopesticide was found to impact both phenotypic covariance and genetic correlations over different environments. Negative genetic correlations were found in the higher doses for pupal mass and development rate in a resource poor environment while in a rich environment the genetic correlations were mostly positive. This indicates that there is allocation variance revealed in high stress environments that might be masked during favorable conditions. Correlations between survival and pupal mass as well as development rate, were mostly centered around zero. Some deviations from zero in both negative and positive directions were found for survival and pupal mass in a rich environment, and survival and development rate in a poor environment. Although, the results for the maximum dose for the survival analyses can be unreliable due to a high number of deaths, there are still interesting patterns in the rest of the treatments worth expanding on. The results show that environment has an impact when it comes to how much of the genetic variance within a population is acquisitional vs. allocational. This is especially important in the context of biopesticide usage and my thesis demonstrates the need for considering environmental impacts and not only genetic diversity when studying adaptation.