2017-08-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/648616摘要：新種形成的遺傳機制一直是演化學研究的主題。異域種化模型認為物種經過隔離而形成，因此基因組內不同區域的分化程度應該是相當均值的。而根據種化基因交流假說，基因組內與物種形成有關的基因會因為天擇的干預不易在兩物種間交換。在其它基因可以交流的情況下，前述區域會在基因組內形成相對歧異度較大的區段或稱為。然而種化過程中，在天擇的影響下如果基因組內部突變率或是基因互換率有差異，即便沒有基因交流，也會造成不同區域分化程度的差異。因此問題在於如何區別基因組內的分化不均值性是由基因交流所造成。種化基因交流模型具體的指出基因組內與種間差異有關的基因會有較大程度的分化，而異域種化模型則沒有這樣的推測。本研究預計整合族群分化以及與物種性狀有關的遺傳學研究來探討基因交流在物種形成時所扮演的角色。我們首先會以模式物種黑腹果蠅進行先期研究。黑腹果蠅的兩個品系，Z and M，有不同的交配行為，而影響這些行為的基因主要在體染色體。因此我們預測Z/M 兩品系果蠅的體染色體比性染色體要有較大的分化。此外過去研究發現薜荔與愛玉小蜂小蜂因為不同生活環境，而有不同的溫度適應。我們預測兩者之間與能量產生有關的基因比起其他的基因會有較大的分化。<br> Abstract: The genetic details of how new species arise have been major topics of evolutionary research. Allopatricmode speciation considers that all genes between two species were diverged at the same time, thus geneticdifferentiation across the genomes between two species should be homogenous. An alternative model ofspeciation with gene flow presumes that the loci involved in reproductive isolation or ecologicalspecialization would result in strong selection against their introgression between species, leading toheterogeneous pattern or “genomic islands” of differentiation in the genome. Nevertheless, level ofdivergence between two species can be heterogeneous in the absence of gene flow, if some biologicalprocesses, including variation in local mutation and recombination rates and selection, have been involved.The problem is whether the observed heterogeneous landscape of genomic differentiation can be explainedsolely by a combination of several biological processes, or gene flow has to be invoked. Speciation with geneflow specifically predicts that genomic regions with elevated divergence will contain genes responsible forspecies isolation, whereas other models make no such prediction. This proposal aims to test the speciationwith gene flow model by integrating studies of population differentiation with genetic studies of phenotypesresponsible for species distinction.We first conduct a pilot study on model organism, Drosophila melanogaster. The genes responsible forbehavior differences between two races, Z and M, are majorly mapped on autosomes. Thus, we expectautosomal loci exhibit greater divergence than X-linked loci. We next test this hypothesis on fig wasps.Jelly-fig wasp, Wiebesia pumilae, which is the pollinator of endemic fig tree, Ficus pumilae var. awkeotsangor jelly fig, and creeping-fig wasp, pollinator of F. pumilae var. pumila or creeping fig. From previousstudies, two fig wasps are separated by different altitudes of their host figs, > 800 m for jelly fig and < 500 mfor creeping fig. While two wasps show different temperature adaptations related to their different livingenvironments, gene flow between them is observed. Therefore, we should expect to see the elevateddivergence in the genetic regions responsible for energy production and metabolism. The divergence in therest of genome would be homogenous because of constant gene flow.