黑皮旗魚在太平洋及東印度洋之族群遺傳結構和族群變動史

Abstract

黑皮旗魚是一種棲息於熱帶、亞熱帶及溫帶水域的世界性魚種。儘管本種在漁業上有其重要的經濟價值，但此物種之族群結構在某些海域所知甚少，特別是在擁有最高漁獲量的太平洋及漁獲量逐年增加且面臨過漁的印度洋。在台灣本地市場可採集到粗或細鱗兩種形態特徵的黑皮旗魚。利用粒線體DNA序列長度為1140個鹼基對的細胞色素b和905個鹼基對的控制區域進行親緣關係分析(phylogenetic analysis)，發現兩種不同外型的黑皮旗魚係屬於同一物種。本研究共採集183個太平洋和印度洋樣本，其中包括三個太平洋採樣區，東太平洋54個標本，西北太平洋56個標本，南中國海40個標本;一個印度洋採樣區33個標本，以粒線體DNA之控制區域分析，發現這些黑皮旗魚皆為同一個演化支(clade)-遍在演化支(ubiquitous clade)。目前太平洋和印度洋的黑皮旗魚資源分別由兩個區域性漁業管理組織（中西太平洋漁業委員會WCPFC及印度洋鮪魚委員會IOTC）來管理。本研究利用粒線體DNA中的細胞色素b和控制區域分析太平洋和東印度洋黑皮旗魚的族群結構，結果發現固定指標(ΦST)、分子變異的階層分析(AMOVA)和分子變異的空間分析(SAMOVA)皆支持黑皮旗魚在東印度洋和太平洋間無族群分化的現象，故而應屬於單一系群。所有東印度洋和太平洋黑皮旗魚皆擁有高的基因型歧異度和低的核甘酸歧異度。中性測試、分佈落差(pairwise mismatch distribution)和貝氏天際線分析(Bayesian skyline analysis)皆顯示東印度洋和太平洋黑皮旗魚在0.3至0.74百萬年前遭遇快速族群擴張。 本研究顯示太平洋和東印度洋的黑皮旗魚為單一系群，此項發現對往後該資源之評估研究提供非常重要的資訊，將有助於該黑皮旗魚資源之進一步保育管理與永續利用。

Blue marlin (Makaira nigricans) is a species that inhabits tropical, subtropical, and temperate waters worldwide. While blue marlin is economically important for fisheries, there are regions in this species’ distribution where little is known about its population structure. This is especially true in the Pacific Ocean, which yields the largest catch of blue marlin, and in the Indian Ocean, where catch has increased consistently over the years and the area is commonly overfished. Sampled Taiwan local market blue marlin shows two morphological characteristics of thick or thin scales. Phylogenetic analysis for taxonomy by mitochondrial DNA (mtDNA) cytochrome b (cyt b) (1140 bp) and control region (CR) (905 bp), these two morphological characteristics of the blue marlin belong to the same species. A total of 183 blue marlin was collected from three Pacific localities, eastern Pacific (EP) (n= 54), western North Pacific (WNP) (n= 56), and South China Sea (SCS) (n= 40) and one Indian Ocean locality (EI) (n= 33), analysis of mtDNA CR revealed that these are both of the ubiquitous clade. Currently blue marlin in the Pacific and Indian Oceans are managed as two distinct management units (the Western and Central Pacific Fisheries Commission [WCPFC] and the Indian Ocean Tuna Commission [IOTC]). This study investigated the genetic structure of blue marlin population inhabiting the Pacific and eastern Indian Oceans based on mtDNA cyt b and CR sequence variation. The results of pairwise ΦST, hierarchical analysis of molecular variance (AMOVA), and spatial analysis of molecular variance (SAMOVA) all support that there is no population differentiation among eastern Indian and Pacific blue marlin, thereby the population are comprised of a single stock. All eastern Indian and Pacific blue marlin possess high haplotype diversity (h) and low nucleotide diversity (π). Neutrality tests, pairwise mismatch distribution, and Bayesian skyline analysis all indicate that eastern Indian and Pacific blue marlin have undergone a rapid population expansion on the order of 0.30 to 0.74 million years ago. This study demonstrates that blue marlin in the Pacific and eastern Indian Oceans constitute a single genetic stock, which provides very important information for stock assessment purpose and for further conservation and sustainable utilization of this resource.