Project Details
Projekt
Detecting the genomic imprints of extreme sexual selection - Genetic architecture of SSD and male self-sacrificial traits in a sexually cannibalistic widow spider
Subject Area
Evolution, Anthropology
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 458109219
Recent advances in high throughput sequencing technology offer unprecedented opportunities to unravel the genetic basis of complex traits at reasonable costs. Here we propose to study the inheritance and the genetic architecture of a combination of adaptations that evolved under sexual conflict. The Australian redback spider, Latrodectus hasselti, has become a textbook example for suicidal mating. Courting males perform a spectacular backwards somersault that brings their abdomen directly onto the female chelicerae. This peculiar behaviour invites cannibalism but also prolongs copulation. Curiously, the males can survive injuries during a 1st copulation inflicted by the female by constricting their abdomen. Males secure paternity by breaking off a terminal sclerite of the sperm-transferring embolus inside the female insemination duct, which then functions as a plug. This trait set is part of a monogynous mating system in which males are selected to invest terminally in mating and securing paternity with a single female. Monogyny co-occurs with a male biased sex-ratio and male dwarfism. Interestingly, the redback spider’s sister species L. katipo from New Zealand is distinguished by a very different mating system. Females of L. katipo are neither aggressive nor cannibalistic and the males do not somersault and can mate multiple times. Sexual size dimorphism is also less pronounced. The two species diverged only recently and are known to hybridize and produce fertile offspring. Previous experiments have shown that 3 generations can be raised within a single year. This species pair of black widows is thus ideally suited to unravel the genetic architecture of the evolution of complex mating systems. We plan to crossbreed the two species in the lab to achieve F1 hybrids that will be crossed and backcrossed with males from both paternal species. We will document inheritance and segregation of 4 related mating traits, (i) the somersaulting, (ii) the abdominal construction that helps males survive copulation, (iii) the mating plug and (iv) male adult body size, in the F2 generation. Additionally, we will sequence the target species’ genomes and perform population genomic as well as QTL mapping analysis of the studied mating traits. Finally, we will dissect male brains and compare gene-expression between males that vary in self-sacrificial behaviour. The research project will reveal unparalleled insights into the genetic architecture of traits that evolved rapidly and likely in concert under sexual selection. We will also lay the foundation for multiple further approaches that e.g. incorporate concerted evolution in both sexes and may eventually permit a reconstruction of sexually antagonistic co-evolution in an unusual mating system.
DFG Programme
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