Testing the effectiveness and repeatability of genetic rescue from inbreeding depression in Tribolium castaneum

Lead Research Organisation: University of East Anglia
Department Name: Biological Sciences

Abstract

BACKGROUND: When populations become depleted or isolated, reduced genetic variation can lead to reduced population fitness through inbreeding depression. The environmental circumstances leading to this situation are only likely to increase in the future, and genetic variation is now recognised by the IUCN as a conservation priority. There is therefore a pressing requirement to address research questions in conservation genetics, with a recent high-impact review identifying priorities for understanding the primary phenotypic routes to inbreeding depression, and whether inbred populations can be 'rescued' through the introduction of new genetic variation from related individuals. Problems identified by this review were: (a) wild studies usually failed to control for potential environmental confounds known to influence fitness; (b) for many systems, the specific phenotypic routes to inbreeding depression within 'fecundity' remain unconfirmed, so a wider range of more detailed reproductive trait measures are required; and (c) the potential for outbreeding depression via disruption of local adaptation is an important consideration and therefore assessment to the F2 generation and beyond (when unlinked genes begin recombining) is required. This project aims to overcome these weaknesses using a controlled, multi-generational and replicated experimental approach. THE MODEL: The flour beetle Tribolium castaneum has been successfully employed as a laboratory system for answering questions in evolution and ecology. Our recent experience with this system through a recent NERC project mean we have detailed familiarity with measuring a range of reproductive fitness traits. We also have an established phylogeny for 50 strains at UEA, so we can objectively identify populations with increasingly-distant genetic backgrounds, and assess their relative impact on genetic rescue. Importantly, we have consistent inbreeding depression of reproductive output for 20 replicate inbred populations, by comparison with similarly-bred controls. METHODS: We have two general aims: (1) conduct detailed measurement of a number of potential reproductive fitness traits to identify which are responsible for inbreeding depression, and (2) measurement of the consistency and effectiveness of 'genetic rescue' under different but controlled conditions. (1) Most examples of inbreeding depression occur via disruption to reproduction. We plan to determine whether different reproductive traits are more susceptible to inbreeding depression using 20 inbred replicate populations and 10 non-inbred controls, across 4 increasing inbreeding coefficients. Detailed and replicated measurement of 15 established reproductive fitness traits (from sperm quality and competitiveness to female egg output and larval hatch) will allow assessment of the specific reproductive phenotypes responsible for depression. (2) Genetic rescue might be possible with even small numbers of 'immigrants'. We will assess genetic rescue in our established inbred lines (and non-inbred controls) using introgression of 4 different populations of known genetic relatedness from a previous project. Using a five-fold range of immigration, coupled with monitoring of genotypic spread measured using phenotypic markers, we will be able to establish how much introgression can rescue an inbred population, and how different genetic backgrounds play a role. Importantly, we will monitor across 3 generations, to determine the likely role of outbreeding depression through loss of local adaptation genes that might occur in the second generation. CONCLUSIONS: Our results will inform conservation management programs concerned about inbreeding by (1) allowing targeted screening of susceptible traits, and (2) whether genetic rescue should be instigated according to the choice of immigrant genes and the risk of outbreeding depression. Material from our experiments will be freely available for further genomic analyses.

Publications

10 25 50

publication icon
Gage MJ (2012) Complex sperm evolution. in Proceedings of the National Academy of Sciences of the United States of America

publication icon
Hangartner S (2015) Experimental removal of sexual selection leads to decreased investment in an immune component in female Tribolium castaneum. in Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases

publication icon
Michalczyk L (2011) Inbreeding promotes female promiscuity. in Science (New York, N.Y.)

 
Description We have discovered that genetic rescue from inbreeding depression can be achieved by female mating pattern, suggesting mechanisms that bias fertilisation or sperm use from more compatible males in the context of inbreeding. Then, haven created experimental bottlenecks, we showed that female mating pattern changed in a manner that would allow greater protection from inbreeding through mating more promiscuously.
We have discovered that sexual selection as a result of mating pattern helps populations to purge negative mutation load from the lineages, providing important empirical evidence for why sexual reproduction persists as a widely-employed mechanism to produce offspring.
Exploitation Route To allow basic understanding of the evolution of costly female promiscuity, and to recognise the importance of female mating pattern for protecting the underlying genetic health of a population.
Sectors Environment

URL http://planetearth.nerc.ac.uk/news/story.aspx?id=1067&cookieConsent=A
 
Description To educate the public on what drives the evolution of a diverse array of animal mating patterns across species. To understand the importance of evolved mating patterns for conservation genetics.
First Year Of Impact 2015
Sector Environment
Impact Types Societal

 
Description Explanation of research findings 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Article reached broad scientific NERC audience

More planet earth articles requested
Year(s) Of Engagement Activity 2011,2014,2015
URL http://planetearth.nerc.ac.uk/news/story.aspx?id=1067
 
Description YouTube video 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Film inspired questions and contact

After broadcasting I was contacted online by a number of correspondents
Year(s) Of Engagement Activity 2011
URL https://www.uea.ac.uk/biological-sciences/people/profile/m-gage#researchTab