台灣油杉之族群遺傳及適應性演化

Abstract

台灣油杉（Keteleeria davidiana var. formosana Hay.）屬松科植物，為台灣特有種。前人研究指出族群間斷分布容易導致族群間基因交流受阻，以至於族群間分化程度逐漸增加，於演化歷程中可能趨於形成在地適應性(local adaptation)之物種，甚至可能發生異域種化(allopatric speciation)的現象。台灣油杉分布於本島之兩端，呈現間斷分布。本研究目的為探討台灣油杉族群間遺傳分化情形，是否因棲地環境明顯差異而產生在地適應性演化。本研究使用擴增片段長度多態性 (amplified fragment length polymorphism, AFLP)的分子標記，共使用12組引子擴增，獲得465個有效條帶。依據STRUCTURE結果可將台灣油杉分為2個歸群。分析族群結構時發現台灣油杉南北部族群間具有顯著遺傳分化，台東大武30林班及41林班也具有顯著分化現象。族群間基因交流與地理距離呈現顯著正相關。中性檢測，發現台灣油杉族群內共有27個偏離中性演化的基因座，其中有11個與環境因子呈現顯著關連性。經連鎖不平衡之檢測，發現台灣油杉族群內具有不同的連鎖區域，推測台灣油杉可能受到地理距離與分歧型天擇的影響，產生不同的適應性演化，族群基因組已有分化現象。

Keteleeria davidiana var. formosana (Pinaceae) is endemic to Taiwan. K. davidiana var. formosana distributed disjunctly in rocky ridges of northern and southern tips of Taiwan. Therefore, this species may provide as an invaluable material for the study of allopatric speciation in plants. Therefore, the main purpose of this study is to understand the patterns of genetic diversity and the spatial genetic structure of this species and formulate the fundamental information of widely separated northern and southern populations of this species by using Amplified fragment length polymorphism (AFLP). A total of 465 bands were detected by the 12 AFLP primer sets. According to the results of STRUCTURE and AMOVA, populations were clustered into two groups, northern and southern groups. Moreover, isolation by distance test showed that the differentiation is between populations associated with geographic distances. We also found population DO and EO differentiated significantly in southern group. Through the outlier-detected methods, we found 27 loci which deviated from neutral evolution, of which 11 showed significant association with environmental factors. The detection of different linkage disequilibrium patterns in the K. davidiana var. formosana populations, indicating different linkage blocks within each population. We speculated that the differentiation among K. davidiana var. formosana population may be effected by geographic distances and differential selective pressures among habitats, which would promote adaptive evolution.