Table of Contents
International Journal of Evolutionary Biology
Volume 2012, Article ID 935970, 12 pages
http://dx.doi.org/10.1155/2012/935970
Research Article

Drosophila melanogaster Selection for Survival of Bacillus cereus Infection: Life History Trait Indirect Responses

1Department of Food Science and Technology, University of Nebraska Lincoln, Lincoln, NE 68583, USA
2Department of Statistics, University of Nebraska Lincoln, Lincoln, NE 68583, USA
3School of Biological Sciences, University of Nebraska Lincoln, Lincoln, NE 68588, USA

Received 24 April 2012; Revised 26 July 2012; Accepted 16 August 2012

Academic Editor: Alberto Civetta

Copyright © 2012 Junjie Ma et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

To study evolved resistance/tolerance in an insect model, we carried out an experimental evolution study using D. melanogaster and the opportunistic pathogen B. cereus as the agent of selection. The selected lines evolved a 3.0- to 3.3-log increase in the concentration of spores required for 50% mortality after 18–24 generations of selection. In the absence of any treatment, selected lines evolved an increase in egg production and delayed development time. The latter response could be interpreted as a cost of evolution. Alternatively, delayed development might have been a target of selection resulting in increased adult fat body function including production of antimicrobial peptides, and, incidentally, yolk production for oocytes and eggs. When treated with autoclaved spores, the egg production difference between selected and control lines was abolished, and this response was consistent with the hypothesis of a cost of an induced immune response. Treatment with autoclaved spores also reduced life span in some cases and elicited early-age mortality in the selected and wound-control lines both of which were consistent with the hypothesis of a cost associated with induction of immune responses. In general, assays on egg production yielded key outcomes including the negative effect of autoclaved spores on egg production.