鰟鮍科魚類的親緣關係與一可能推動鰟鮍物種多樣性的演化機制

Abstract

鰟鮍為小型的鯉超科魚類，因其與淡水二枚貝的共演化使其有相當吸引人注意的演化歷程。在此研究中，我們採用了粒線體和核基因序列的變異資訊並依密碼子鹼基位置（codon position）設定後，採用最大似然法與貝葉斯法分析，提出了一個較完善的鰟鮍科魚類物種間的親緣關係樹形圖。分析中包含了41個物種、9個亞種、以及三個尚未描述的物種。我們的發現支持鰟鮍科魚類為一單系群。但目前對鰟鮍魚類分類所採用的三個屬，其中兩個並非單系群。鰟鮍魚類可被分為六個演化支。這些演化支依據他們之間的演化關係與重新評估形態特徵後，可進一步視為六個不同的屬。我們提出以五個屬／演化譜系：鰟鮍屬（Rhodeus）、鱊屬（Acheilognathus）、田中鰟鮍屬（Tanakia）、副田中鰟鮍屬（Paratanakia）、偽鰟鮍屬（Pseudorhodeus），以及一個包含五個目前被歸在鱊屬物種的未命名屬的修正屬級分類處理。利用本研究所建立的親緣關係樹形圖，我們可以更進一步的探討與鰟鮍魚類相關的系統分類、物種鑑定、以及生物地理等演化議題。 異域種化與對二枚貝寄主偏好的轉變都被提出作為鰟鮍物種分化的主要原因。本研究亦藉由研究兩親緣相近但表現不同婚姻色的副田中鰟鮍亞種（Paratanakia himantegus himantegus 和 P. h. chii）其棲息地環境光譜與其視覺光譜關係，我們推論出感覺推動物種形成機制也可能促進了鰟鮍魚類的多樣性。

Bitterlings are extremely interesting evolutionarily due to their unusual reproductive behaviors and their coevolutionary relationships with freshwater mussels. In this study, we provide the most comprehensive phylogenetic reconstruction of species relationships of the group based on partitioned maximum likelihood and Bayesian methods using DNA sequence variation of nuclear and mitochondrial genes on 41 species, 9 subspecies and three undescribed species. Our findings support the monophyly of the Acheilognathidae. Two of the three currently recognized genera are not monophyletic and the family can be subdivided into six clades. These clades are further regarded as genera based on both their phylogenetic relationships and a reappraisal of morphological characters. We present a revised genus-level classification for the Acheilognathidae with five genera/lineages: Rhodeus, Acheilognathus (new constitution), Tanakia (new constitution), Paratanakia gen. nov., and Pseudorhodeus gen. nov. and an unnamed clade containing five species currently referred to as “Acheilognathus”. Using our new phylogenetic framework, we discuss the evolution of the Acheilognathidae relative to classification, taxonomy and biogeography. Allopatric speciation and switches in mussel host preference have been suggested to be the main factors of bitterling diversification. By studying the correlation between the photic conditions of the habitats and the visual spectra of two closely related bitterlings (Paratanakia himantegus himantegus and Paratanakia himantegus chii) with different male nuptial colorations, we conjecture that the semsory drive speciation may also promote the diversity of bitterling fishes.