以谱系地理辅助嗜尸性丽蝇发育历期数据用于PMI推断的研究

Developmental duration data of necrophagous blow fly has great importance in the estimation of post-mortem interval (PMI). However, the developmental data among geographical populations have low reference value. Significant deviation between PMI estimation and actual value could be caused by directly applying developmental data of other geographical populations to a local population of the same species. It is urgent to tackle this barrier for its impact on the accuracy and popularity of inference method. Based on our previous study, Aldrichina grahami exhibits typical necrophagous behavior, broadly geographic distribution with rich genetic diversity. Using methodology of phylogeographic to analysis the genetic divergence between populations, then combing with difference of developmental duration data should make a breakthrough at this problem which shared by necrophagous blow flies. The present project takes A. grahami for research objects, based on the accomplishment of its whole genome sequencing and broad sampling. At first step, we screen out genetic markers using resequencing technology, then analysis difference of genetic diversity among geographical populations using phylogeographic methods. Secondly, we chose resampling regions based on populations clustering results, recapture samples and collect development data for developmental duration model construction, then make comparison on divergence of inter-populations development. We further investigate the variation and relevance at genetic and genotypes level among populations which resulted from adaptation into different environment. Thirdly, we set genetic divergence as coefficient of variation to optimize the developmental duration based late PMI estimation model. It will finally provide theoretical basis for the reference and utility of developmental duration data from different blow fly populations.

嗜尸性丽蝇发育历期数据对晚期PMI推断具有重要意义。但地理种群间发育相关数据缺乏参考性，将异地种群数据套用于同种本地种群可导致PMI结论与实际值出现显著偏差，是当前影响推断方法准确性和普及亟待解决的问题。我们前期研究发现巨尾阿丽蝇嗜尸行为典型，地理分布广泛且种群遗传多态性丰富。借助谱系地理方法分析其种群间遗传分化，结合发育历期差异，有望突破嗜尸性丽蝇的这一共同难题。本项目以该蝇为研究对象，在已完成其基因组测序及广域采样的基础上：1）通过重测序技术筛选遗传标记，以谱系地理方法分析地理种群间遗传多态性差异；2）依据种群聚类结果选取样本补采地，补采样本并以发育数据建立发育历期模型，比较种群间发育差异，进而分析种群间为适应不同生境而在遗传和表型水平发生的改变及其相关性；3）以遗传差异为变异系数，优化基于发育历期数据的晚期PMI推断模型。最终为嗜尸性丽蝇种群间发育历期数据的参考和利用提供理论依据。

嗜尸性丽蝇发育历期数据对晚期PMI推断具有重要意义。但地理种群间发育相关数据缺乏参考性，将异地种群数据套用于同种本地种群可导致PMI结论与实际值出现显著偏差，是当前影响推断方法准确性和普及亟待解决的问题。前期研究发现巨尾阿丽蝇嗜尸行为典型，地理分布广泛且种群遗传多态性丰富。借助谱系地理方法分析其种群间遗传分化，结合发育历期差异，有望突破嗜尸性丽蝇的这一共同难题。本项目在前期研究基础之上，开展以下几方面工作，1）通过重测序技术筛选遗传标记，以谱系地理方法分析地理种群间遗传多态性差异；2）依据种群聚类结果选取样本补采地，补采样本并以发育数据建立发育历期模型，比较种群间发育差异，进而分析种群间为适应不同生境而在遗传和表型水平发生的改变及其相关性；3）以遗传差异为变异系数，优化基于发育历期数据的晚期PMI推断模型。 .项目进展期间由于疫情原因，地理种群补采工作受到一定程度影响，但申请人对研究方案及时调整，保障了项目的整体有序开展。目前已完成巨尾阿丽蝇幼虫各龄期、蛹期发育转录组测序，结合全基因组数据，进行了全面分析和深入挖掘，得到以下几方面重要结果，（1）构建了11个嗜尸性行为相关特征基因库，为后续基因功能研究提供了大量备选基因；（2）构建可用于死亡时间推断的趋势表达基因簇2个，筛选出可用于幼虫龄期鉴定的特征库4个；（3）完成了国际上首个交互式嗜尸性蝇类组学专题数据库，已上线试用版，功能模块和系统开发在进一步优化中。.同时，基于对巨尾阿丽蝇嗜尸性行为机制的思考，完成了该蝇种触角蛋白质组和嗅觉转录组的解析工作，并通过行为学实验进行了验证，鉴定出影响嗜尸性行为的嗅觉关键基因用于后续研究。除此之外，申请人还对嗜尸性昆虫肠道微生物、尸体VOCs、嗜尸性甲虫的多样性和种群差异等方面进行了初步探索，为嗜尸性昆虫的整体化、系统化研究打下了基础。.相关成果已陆续发表，更多数据仍在进一步整理和撰写中。

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