中華珈蟌族群之地理分化與保育研究

Abstract

為探討中華珈蟌 (Psolodesmus mandarinus) 三亞種親緣關係及翅色地理變異，本研究利用分子、形態與行為等方法整合分析並據此提出保育策略。首先，由細胞核與粒線體基因親緣分析結果，日本八重山族群 (即黑岩亞種 subspecies kuroiwae) 與台灣族群 (包括北台亞種 subspecies mandarinus與南台亞種 subspecies dorothea) 隸屬不同進化支序。在粒線體基因上，台灣產者又分為東部與西部分子支序。東部分支皆屬南台亞種個體，西部分支則包括北台與南台二亞種個體。由於台灣西北部族群遺傳多樣性較低，且大部分個體與南部共享一常見單倍型，因此北台亞種可能是南台亞種向北拓殖所形成之亞種。其次，利用翅痣形態測量分析，日本八重山族群 (即黑岩亞種) 與台灣族群 (包括北台與南台亞種) 可正確鑑別。往昔以翅色區分台灣產北台與南台亞種，經翅色與緯度的迴歸分析結果，翅色在北台灣為漸變形式，並無法有效釐清二亞種與其分布。反之，雌蟲翅面積在北緯24.19度 (約位於台灣中、北部交接處) 有一間斷變化，此緯度與現行區分二亞種分布範圍的北緯24.33度接近。由於屬於生活史性狀之一的雌蟲翅面積與翅色特徵的變化皆在北台灣，故兩者可能形成共同適應複合體，以適應北台灣不同選汰環境。第三，野外族群生殖配對行為研究結果顯示，台灣產北台與南台亞種雌蟲對雄蟲誇示翅色皆有相同偏好，因此無法單以雌蟲翅色偏好之性選汰解釋二亞種翅色差異。由於生活史性狀與翅色特徵僅在北台灣族群形成共同適應複合體，推論二亞種雌蟲相同翅色偏好應有不同適應度。即北台灣北台亞種雌蟲對誇示翅色偏好，可符合生活史與翅色之共同適應複合體，故翅色可由透翅型逐漸轉變為誇示翅色型。反之，台灣中、南部之南台亞種雌蟲翅色偏好並無法符合此適應性，故仍維持原有透翅型。最後，本研究強調中華珈蟌為台灣與八重山地區唯一特有屬豆娘，其翅色進化又是生物多樣性教育良好案例，也可作為溪流生態與氣候暖化之生物指標，後續需發展生態遊學相關計畫，達到研究、保育與資源永續利用之三贏目標。

To investigate the phylogenetic relationship and geographical variation of wing color among the Psolodesmus mandarinus three subspecies, a combination of molecular, morphological, and behavioral approaches was used to guide this research and develop the conservation strategies. Firstly, the molecular phylogenetic analysis of nuclear and mitochondrial genes revealed considerable divergence between Yaeyama’s populations (subspecies kuroiwae) and Taiwanese populations (included subspecies mandarinus and dorothea). Furthermore, two mitochondrial lineages (east and west) existed in Taiwan. The eastern Taiwan lineage included these individuals belonging to dorothea, and the western Taiwan lineage included both dorothea and mandarinus. Because of the genetic diversity of mitochondrial gene was much lower in northwestern Taiwan region and two subspecies shared a common haplotype, it is probable the populations of manadrinus were derived from the northward expansion of dorothea populations. Secondarily, Yaeyama’s populations (kuroiwae) and Taiwanese populations (mandarinus and dorothea) could be exactly discriminated by the morphometrical analysis of wing pterostigma. Previous studies reported the wing color differences between mandarinus and dorothea, our results illustrated that the wing color traits gradually changed across the populations in northern Taiwan. It would be hard to discriminate two subspecies and determine the distribution limits. In contrast, the female wing size shifted dramatically at 24.19 degree (between central and northern Taiwan) which was close to the current criteria (24.33 degree) for dividing two subspecies. Because of both the wing color trait and female wing size changed across the populations of manadrinus in northern Taiwan, it is probable these traits may form co-adapted trait complexes and to cope with a different selection regime in northern Taiwan. Thirdly, the field observations of mating behavior in mandarinus and dorothea populations demonstrated that two subspecies possessed the same kind of female preference for exaggerated male coloration. Thus, the differentiation of wing color trait could not be interpreted only by using sexual selection. If the wing color trait and life history trait formed co-adapted trait complexes in northern Taiwan, the fitness of female preference would be difference between mandarinus and dorothea. Because of the positive fitness effect in female preference for mandarinus populations, wing color traits gradually changed across the northern Taiwan. On the contrary, the negative fitness effect in female preference for dorothea populations, the hyaline wing is maintained by a combination of sexual selection and natural selection. Finally, Psolodesmus is the only one endemic genus of damselflies in Taiwan and Yaeyama. The variety of wing color provided an ideal explanation case for biodiversity education. It also could be used as a biological indicator for monitoring stream ecosystem and global warming. Above all, we suggested developing an educational and recreational program for pursuing the goals of research, conservation and sustainable utilization.