論文發表人：林秀瑾（加州大學聖地牙哥分校海洋生物所博士班）
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多數的生物都存在有隨著地理位置的種內遺傳變異，這個現象甚至出現在具有漂浮期而能助長遺傳物質交換的海洋魚類身上，藉由比較出現在同地域不同物種的類緣地理學，我們可以了解該生物的演化史以及其與歷史環境的互動。因為擁有多樣棲地及海洋特徵，包含加州灣的東太平洋是一個絕佳研究礁岩魚類演化史的海域。管魚尉魚是一類極有可能因其閉索性生活史而呈現種內變異的礁岩魚類，我們的遺傳研究結果顯示一種加州灣特有的管魚尉魚種Acanthemblemaria crockeri 實際上是兩個被分隔許久且獨立演化的新種，而且它們僅僅在La Paz 海域被３０公里的距離所分隔。然而，此分隔位置並沒有在另一個同地域的姊妹種A. macrospilus中發現，此魚種雖也發現兩個獨立演化的新種，其地理上的分隔線卻是在加州灣和墨西哥西南部之間。該二魚種不但擁有相似的棲地選擇，生活史及攝食偏好，更被相同的海洋環境所環繞，這顯著不同的遺傳變異現象透露除了以上因素之外的可能分隔機制。
Nearly all taxonomic groups exhibit genetic differences across their geographical distributions. This is true even in groups such as marine fishes which have a pelagic larval dispersal (PLD) stage that often facilitates gene flow. Comparison of phylogeography among sympatric species is widely used for examining the evolutionary history of organisms as well as how that history is related to present-day and historical environments. The Tropical Eastern Pacific, including the Gulf of California, is an ideal region for studying this issue in reef fishes because of possible habitat barriers and oceanographic features. Chaenopsids are a lineage of reef fish with restricted life-history traits and thus great potential for resolving evolutionary enigmas. One Gulf of California endemic chaenopsid species, Acanthemblemaria crockeri, shows two reciprocally monophyletic lineages with deep divergence (HKY+I distance = 11.9% for COI) separated by a 30 km gap north of the La Paz region. However, a closely-related and co-occurring species, A. macrospilus, shows no divergence within the Gulf based on either COI or D-loop. Instead, the Gulf and southern Mexico populations of A. macrospilus are reciprocally monophyletic lineages (HKY+I distance = 15.3% for COI) separated by the Sinaloan Gap. Acanthemblemaria crockeri and A. macrospilus have similar habitat preferences, life history and feeding habits. In addition, they are exposed to similar physical oceanographic features in the area of sympatry. Their significantly different genetic patterns suggest factors other than life history or oceanography may underlie their phylogeographic patterns.
