尖葉楓與台灣紅榨槭種間的基因漸滲與氣候之關聯

Abstract

物種間的雜交能增加物種對於新環境的適應潛能。在此研究中我利用基因組尺度的遺傳資料檢驗兩個高度分化的楓屬物種間的雜交與天擇，並驗證跨越不同環境下的適應。我從全台灣跨越高低海拔的採集這兩個遺傳上有分化的尖葉楓(Acer caudatifolium)與台灣紅榨槭(A. rubescens)，共271個個體，利用multiple shotgun sequencing所獲得的3281個單一核甘酸多型性檢驗物種間的基因漸滲。族群結構分析與演化模型都指出尖葉楓與台灣紅榨槭間有次級接觸和基因漸滲。基因組-環境相關性分析則顯示這兩個物種在環境上分化。在3281個SNP中有16個SNP是在種間高度分化、與環境因子相關且有基因漸滲的。然而根據CCA的結果卻顯示遺傳混雜的個體並沒有分布在不同於親本的環境。從這些結果指出在高度分化的兩個物種也能有基因漸滲的可能，但大多被物種間的屏障所限制。然而尖葉楓與台灣紅榨槭間的基因漸滲沒有辦法證明與異質環境的適應之間的相關性。

Interspecific hybridization may enhance the capacity of species to adapt to novel environment, and selection not only promote adaptive introgression but also act to maintain species boundaries. In this study, I used genome-wide estimates of admixture and selection to examine the introgression between two genetically differentiated Acer species, and testing adaptation across heterogeneous environments. Introgression was examined for 271 individuals of Acer caudatifolium and A. rubescens collected from Taiwan island spanning from low altitude to high altitude using a panel of 3281 single nucleotide polymorphisms with multiple shotgun sequencing. Both the population structure and demographic model point to secondary contact model and introgression between Acer caudatifolium and A. rubescens. Genome-wide environment association analyses show they are ecologically differentiated. 16 of the 3281 SNP are high divergence, associated with environment factor and introgressed. However, results of CCA show that genetic admixture individuals of sink species do not show the same environmental similarities with source species. These results indicate that high divergence SNPs may introgression between two genetically differentiated species but most were restricted by species boundary. Introgression between A. caudatifolium and A. rubescens were failed to find association with adaptation across heterogeneous environments.