- 學位論文
臺灣陽明山向天池鰓足類（甲殼亞門：鰓足綱）的生物多樣性、幼體發育及溫度對其生活史特徵的影響
Diversity, larval development and temperature influence on life history traits of branchiopod species (Crustacea: Branchiopoda) in Siangtian Pond of Yangmingshan, Taiwan
摘要
陽明山國家公園西側向天池中，有三種共域、共存的大型鰓足類動物，包括一種豐年蝦（鵠沼枝額蟲，已知學名為Branchinella kugenumaensis (Ishidawa, 1895)）及兩種蚌蝦（學名尚未確定），本論文主旨乃探究其生活史模式與生態棲位分化機制。首先以電子顯微技術（包括卵、幼體、成體之SEM相片）及粒線體DNA序列（包括12S、16S、COI三種探針），進行形態與分子之比對，發現向天池中的兩種蚌蝦分別與日本真湖蚌蟲（Eulimnadia braueriana Ishikawa, 1895）和日本貓眼蚌蟲（Lynceus biformis (Ishidawa, 1895)）近似，然而兩兩之間存有些許的表型變異與遺傳差異（第二、三章）。其中，向天池真湖蚌蟲為新種（Eulimnadia sp. nov.），而向天池貓眼蚌蟲（Lynceus biformis）與日本同種。然後針對此三種共域之大型鰓足類動物，進行生活史特徵（如：最早孵化時間、最早性成熟時間、最長壽命、體長成長曲線、存活曲線、性別比例、窩卵數等）之測量與觀察，包括實驗室養殖（第四、五章）與野外調查（第六章），並檢視溫度對生活史策略的影響。結果發現，新種真湖蚌蟲為性比4.5%的雄暨同體型動物，對溫度的適應性在三者中最廣（如：15、20、25、30oC），並展現對溫度的生殖適應策略。高溫下（如：25、30oC），雄性個體性成熟顯著遲緩，傾向由雌雄同體以自體受精的方式完成有性生殖；低溫下（如：15、20oC），除了自體受精外，雄性個體與雌雄同體同步性成熟，兩者可藉異體受精而產生基因多樣性較高的卵。相較之下，鵠沼枝額蟲偏好低溫（如：15、20、25oC），為雌雄異體的兩性動物，性比平均值53.1%，尤其雄性個體較雌性個體早兩日性成熟，推測其雄性個體之間具有激烈的生殖競爭壓力。貓眼蚌蟲和鵠沼枝額蟲一樣為雌雄異體的兩性動物，然而性比平均值9.1%，且雌雄同步性成熟的現象，推測其雄性之間的有性生殖競爭較鵠沼枝額蟲舒緩。最後，比較這三種共域鰓足類動物之生態棲位分化的機制，雖然鵠沼枝額蟲與新種真湖蚌蟲的體長成長率皆隨溫度上升而增快，然而，高溫下可自體受精的生殖方式，使新種真湖蚌蟲的族群成長率在高溫下明顯增加，展現優於鵠沼枝額蟲的溫度適應力與高溫優勢。至於貓眼蚌蟲，由於其對溫度沒有明顯偏好，且難以在實驗室中培養，推測其生活史策略可能受其他因子影響。
並列摘要
Three large branchiopods, including one fairy shrimp (Branchinella kugenumaensis (Ishidawa, 1895)) and two clam shrimp species (without confirmed species names updated), co-inhabit in Siangtian Pond, Yangmingshan National Park, Taipei, Taiwan. This dissertation is aimed to explore their life history patterns and nich differentiation mechanisms. First of all, I identified the two clam shrimp species using SEM photography (including eggs, nauplii, and adults) and three mitochondrial DNA markers (i.e. 12S, 16S, COI). The morphological and molecular evidences showed that both clam shrimps in Siangtian Pond were very similar to the Japanese Eulimnadia braueriana Ishikawa, 1895 and Lynceus biformis (Ishidawa, 1895), while showed some phenotypic variations and genetic distances (Chapter 2 and 3). These two species were confirmed as Eulimnadia sp. nov. and Lynceus biformis. Next, I observed and measured life history traits (i.e. earliest hatching time (EHT), earliest maturation time (EMT), maximum lifespan (MLS), grwoth curve of body length, survival curve, sex ratio, clutch size, etc.) of these three sympatreic large branchiopods, either in aquacutural setting (Chapter 4 and 5) or in field (Chapter 6), and tried to explore the temperature effect on its life history strategies. I found Eulimnadia sp. nov. was an androdioecious animal with sex ratio of 4.5%. It adapted to wider temperature range (e.g. 15, 20, 25, 30oC) with reproductive flexibility. At higher temperature (e.g. 25, 30oC), male matured significantly slower than hermaphrodite, and only hermaphroditic eggs were quickly produced by selfing. However, at lower temperature (e.g. 15, 20oC), male matured with no significant difference than hermaphrodite and gonochoric eggs (with presumably higher genetic diversity) were reproduced in addition to hermaphroditic eggs. Branchinella kugenumaensis was dioecious with sex ratio of 53.1%. It adapted to lower temperature (e.g. 15, 20 and 25oC) than Eulimnadia sp. nov. with strong male-male competition since male matured signigicantly two days earlier than females. Lynceus biformis was another dioecious branchiopod in Siangtian Pond with smaller sex ratio as 9.1% compared to B. kugenumaensis. Its male and female matured with no significant difference, making lower male-male competition than B. kugenumaensis. Finally, I tried to explore the niche differentiation mechanisms through temperature-dependent life history performances among these three sympatric branchiopods. Both B. kugenumaensis and Eulimnadia sp. nov. grew faster with temperature-dependent manner, Eulimnadia sp. nov. further showed hermaphroditic reproduction and elevated population growth at high temperature, demonstrating its temperature accommodation and thermal superiority. The third species L. biformis was hard to be cultured in laboratory, and its temperature-independent life history characters suggested that this sympatric branchiopod might be influenced by other factors in addition to temperature.
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