鼠尾鱈科魚類（鱈形目：鼠尾鱈科）聚焦於奈氏鱈屬之親緣關係及分類研究

Abstract

鼠尾鱈科是多樣性和豐富度很高的一科深海真骨魚（包括27個屬共計372種）。牠們主要分布在熱帶和亞熱帶海域，尤其是印度-西太平洋地區（包括23個屬共計126種）。而其中五個屬，奈氏鱈屬、庫隆長尾鱈屬、軟首鱈屬、凹腹鱈屬和梭鱈屬因爲其外觀的相似性，而被認為是源自於共同祖先。早期的分子親緣關係研究受限於涵蓋的種類及基因標記的數量，推斷出的親緣關係不夠完整或是不夠具有可信度，導致五個屬及其他屬之間的演化關係未得到解決。奈氏鱈屬是鼠尾鱈科中第三大的屬，包含 54 種物種且多樣性仍未完全被探知。其特徵為具有發達的眶下架和吻兩端的特化鱗片。目前總共有 25種奈氏鱈分布在印度-西太平洋地區。 本研究第一部分使用了新構建的多基因資料集並利用之去測試了五個相似屬之間的演化關係。在研究結果發現，總共有10個鼠尾鱈科的屬為單系群。而縱使上述提及的五個屬形態上相似，分子結果顯示五個屬並不能形成一個單系群，並發現了梭鱈屬與其外觀差異極大的單長尾鱈屬互為姊妹群。此外，本研究發現奈氏鱈屬跟庫隆長尾鱈屬能形成一個單系群，證明了兩個屬的演化相關性，然而兩個屬皆不是單系群，因此建議不再將庫隆長尾鱈視為一個有效屬名。 在第二部分裡，本研究使用綜合分類學的分析方法，探討了印度-西太平洋地區奈氏鱈屬種間層級的多樣性。利用粒線體細胞色素c氧化酶亞基1（COI）資料及進行物種界定並提出初步的物種假設，並使用了形態學、生物地理資訊等其他標準來驗證推斷的物種。在對16個形態種進行了98個樣本的檢查後，最終在確定了20個潛在物種，其中有10個型態種來自於印度-西太平洋地區，表明了奈氏鱈屬存在的隱藏多樣性。本研究在大鱗奈氏鱈種團和長棘奈氏鱈種團中發現了五個隱蔽種，並指出原始奈氏鱈與科氏奈氏鱈的同種性，建議將科氏奈氏鱈視為原始奈氏鱈的同種異名。總體來說，本研究有效地利用分子證據闡明了五個形態相似的屬的演化關係，並為奈氏鱈屬的分類學，尤其是分布在印度-西太平洋地區的物種提供了新的見解。

Macrouridae represents the most dominant teleost fish family in terms of species diversity and abundance in the world's deep oceans, especially from the tropical and subtropical regions. This family, commonly known as grenadiers, rattails, or whiptails, currently comprises 372 valid species in 27 genera. From the Indo-West Pacific (IWP) region, 126 species in 23 genera are found. Five particular genera within the family (Nezumia, Kuronezumia, Malacocephalus, Ventrifossa, and Lucigadus) share similar morphological features and were thought to descent from a common ancestor. The early molecular phylogenetic studies of the Macrouridae were mostly based on limited number of taxa and fewer gene markers. The inferred phylogeny was either incomprehensive or weakly or non-supported, leading to the evolutionary relationships among the five morphologically resembling genera and other genera unresolved. One of the genera, Nezumia, is the third largest genus of the family Macrouridae comprising 54 valid species but its taxonomy has never been throughout studied. The Nezumia species are featured by a well-developed suborbital ridge and tubercle-like scales in the snout. Twenty-five currently recognized Nezumia species are present in the IWP region. In this study, I firstly used a newly constructed multigene dataset to test the evolutionary affinity among the five morphologically resembling genera of the Macrouridae. The inferred phylogeny recovered ten sampled macrourid genera as monophyly. The results also show that these five genera together do not form a monophyletic group and reject thus the hypothesis regarding their closer relationship based on morphology. Instead, I uncover the sister group of Lucigadus is Haplomacrourus, a genus with a distinct feature in the appearance from Lucigadus and its resembling genera. All of the representative taxa from Nezumia and Kuronezumia together still form a monophyletic group, indicating their evolutionary affinity. However, neither of the genera appears to be monophyletic. Herein, I propose that the name “Kuronezumia” is no longer a valid genus name. Secondly, the species-level diversity of Nezumia occurring in the IWP region was explored using the integrated approach in taxonomy. Here, the species delimitation analyses based on the constructed mitochondrial cytochrome c oxidase subunit 1 (COI) gene dataset were conducted to suggest the primary species hypothesis. Other criteria such as the morphology and biogeographic information, were also used to validate the inferred species. A total of 20 species were finally inferred based on the examination of 98 samples in 16 morpho-species among which 10 morpho-species were from IWP region. This finding indicates a presence of hidden diversity of Nezumia species. The five potential new cryptic species were especially discovered in two IWP species groups, Nezumia propinqua group and the Nezumia spinosa group. My results also support the conspecificity of Nezumia coheni and Nezumia proxima, suggesting placing Nezumia coheni in the synonymy of Nezumia proxima. Overall, this study effectively utilized molecular evidence to elucidate the evolutionary relationships of the five morphologically similar genera and provide new insights into the taxonomy of the Nezumia, especially the species occurring in the IWP region.