Detecting the genomic imprints of extreme sexual selection - Genetic architecture of SSD and male self-sacrificial traits in a sexually cannibalistic widow spider

高通量测序技术的最新进展为以合理的成本揭开复杂性状的遗传基础提供了前所未有的机会。在这里，我们建议研究的遗传和遗传结构的适应性，在性冲突下进化的组合。澳大利亚红背蜘蛛，Latrodectus hasselti，已经成为自杀性交配的教科书例子。求偶的雄性会表演一个壮观的后空翻，把它们的腹部直接带到雌性的螯肢上。这种奇特的行为会导致同类相食，但也会导致异交。奇怪的是，雄性在第一次交配时，可以通过收缩腹部而免受雌性的伤害。雄性通过折断雌性受精管内的精子转移栓塞的末端片来确保父子关系，然后它就像塞子一样起作用。这种特征集是一夫一妻制交配系统的一部分，在该系统中，雄性被选择用于最终与单个雌性交配并确保父权。一夫一妻制与偏男性的性别比例和男性侏儒症同时发生。有趣的是，红背蜘蛛的姐妹物种L。来自新西兰的katipo以非常不同的交配系统而闻名。女性L。katipo既不好斗也不吃人，雄性不会翻筋斗，可以多次交配。性别大小二型性也不太明显。这两个物种最近才分化，并且已知杂交并产生可育的后代。以前的实验表明，一年内可以饲养3代。因此，这对黑寡妇非常适合解开复杂交配系统进化的遗传结构。我们计划在实验室中对这两个物种进行杂交，以获得F1杂交种，这些杂交种将与来自两个父系物种的雄性进行杂交和回交。 我们将记录4个相关交配性状的遗传和分离，（i）翻筋斗，（ii）腹部结构，帮助男性生存交配，（iii）交配塞和（iv）男性成年人的身体大小，在F2代。此外，我们还将对目标物种的基因组进行测序，并对所研究的交配性状进行群体基因组和QTL定位分析。最后，我们将解剖男性的大脑，比较不同自我牺牲行为的男性之间的基因表达。该研究项目将揭示对性状遗传结构的无与伦比的见解，这些性状在性选择下迅速进化并可能协同进化。我们还将为多种进一步的方法奠定基础，例如将两性的协同进化纳入其中，并最终可能允许在一个不寻常的交配系统中重建性对抗的共同进化。

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.