台灣芭蕉適應環境的遺傳結構之探究

The genetic architecture of environmental adaptation for the past, present, and future of Musa itinerans

陸政鉞(Cheng-Yueh Lu)

指導教授 ： 李承叡

國立臺灣大學/生命科學院/植物科學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903254

摘要

遺傳結構與其對應的效應值向來是演化生物學的研究核心。冰河時期和亞洲大陸間斷相連的台灣恰為絕佳地點進行該類研究，因其不僅具有大陸族群的既有變異，更有因應新環境被保留的新生突變。此研究著眼於野生種香蕉──台灣芭蕉，並利用生態基因體學的方法檢視其過去至未來的適應進程。遺傳組成與環境因子的顯著相關顯示台灣芭蕉存在在地適應現象，且新生突變與既有變異此二者遺傳結構貢獻不一。數量上，既有變異普遍較新生突變為多；而對於雨量相關的氣候因子，效應值則以新生突變為大，且當該因子相對於中國大陸地區為一嶄新的氣候時，此現象尤為明顯。我們亦著眼於台灣芭蕉未來的適應現象，雖未發現氣候變遷傾向保留任一遺傳結構，但透過物種分布模型與效應值的結合，揭露了適存族群潛在的滅絕風險。此研究不僅演示了遺傳結構──既有變異與新生突變──的適應軌跡，且透過不同模型的整合，指出台灣西南部為台灣芭蕉的易危區域。

關鍵字

效應值 ； 在地適應 ； 既有變異 ； 新生突變 ； 滅絕風險

並列摘要

Genetic architecture of adaptation has been the central focus to evolutionary biology, and effect sizes thereof have been investigated from theory to empirical studies. Taiwan is a perfect place to explore such synthesis of the genetic basis and effect size where standing variations (SV) and new mutations (NM) were established through the recurring connection to East Asian continent at glacial periods. Here, we center on a wild banana Musa itinerans that distributes along altitudinal and latitudinal gradients in Taiwan, and assess the adaptive course from the past to the future. Significant genetics-environment association indicates local adaptation where the assortment of SV and NM contributes differently. While SV are dominant in number, NM exert larger effect size in precipitation-related climates, especially for those novel to mainland China. Under anthropogenic climate change, both SV and NM have no inclination to retain in the future. Incorporation of effect size into species distribution modeling unveils the indiscernible extinction risk of apparently fitting populations. Our results demonstrate the trajectories of adaptive SV and NM, and identify southwestern Taiwan as the most vulnerable region with the integration of universal and locally differential responses of M. itinerans.

並列關鍵字

effect size ； local adaptation ； standing variation ； new mutation ； extinction risk

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