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Unloading a genetic load: costs of inbreeding and their avoidance in a parasitoid wasp with complementary sex determination

English title Unloading a genetic load: costs of inbreeding and their avoidance in a parasitoid wasp with complementary sex determination
Applicant Mazzi Dominique
Number 115980
Funding scheme Project funding
Research institution Gruppe Angewandte Entomologie Institut für Pflanzenwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Agricultural and Forestry Sciences
Start/End 01.09.2007 - 31.08.2010
Approved amount 240'491.00
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All Disciplines (2)

Agricultural and Forestry Sciences

Keywords (6)

cotesia glomerata; diploid males; extinction; inbreeding avoidance; inbreeding depression; kin recognition

Lay Summary (English)

Lay summary
All known members of the insect order Hymenoptera (comprising wasps, bees, ants and sawflies) have haplodiploid sex determination. Males develop from unfertilized eggs, inherit one set of chromosomes from their mother and are thus haploid. Females develop from fertilized eggs, inherit one set of chromosomes each from both their parents and are thus diploid. Hence, generally, in haplodiploids, males and females differ in the number of chromosome sets. However, owing to a peculiar sex determination mechanism known as single-locus complementary sex determination (sl-CSD), diploid males of biparental origin can occur in some species. Under sl-CSD, gender is determined by the genotype at one locus with multiple alleles. Haploids are always males, while diploids are females when heterozygous, but males when homozygous. As diploid males are often inviable or sterile, they impose a genetic load on populations. The odds that mating partners share an allele at the sex locus, thus leading to the production of diploid male offspring, increase when close relatives mates. Therefore, species with sl-CSD are expected to have evolved mechanisms towards the avoidance of inbreeding.Gregarious parasitoid wasp species (those where multiple offspring from one female develop in a single host) are inherently at risk of inbreeding. The co-existence of life-history characteristics conducive to inbreeding and a sex determination mechanism that may impose a substantial fitness penalty under inbreeding is an evolutionary conundrum, whose resolution may lay in the evolution of behavioural strategies that minimize kin mating.We use the parasitoid wasp Cotesia glomerata as a model species to investigate 1) the magnitude of the costs of the genetic load ensuing from sl-CSD, and 2) the effectiveness of behavioural inbreeding avoidance strategies such as natal dispersal and kin recognition in cutting such costs.Results of our work shall deepen our understanding of how species with a life-history that makes them prone to inbreeding cope with the additional handicap of a peculiar sex determination mechanism. The role of Cotesia glomerata as a representative of a group of organisms including providers of key services as biological control agents and as crop and wildflower pollinators further contributes to the implementation of sustainable ecosystem management, as well as to the increasingly urgent conservation of the diversity and density of hymenopterans.
Direct link to Lay Summary Last update: 21.02.2013

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