動物群體繁殖(communal breeding)現象廣泛分佈在不同類群動物，可以由適應性機制(adaptive approach)及副產品機制(by-product approach)去解釋其形成與功能。根據兩個機制的論述，有許多假說相繼被提出以了解群體生殖之發生，但對大部份物種類群（哺乳類及鳥類除外）來說，這種群體生殖是否具任何適應性的價值迄今還是未被探索及未知的。本研究計畫擬以三年時間，利用竹筒可以被操作之特性，在野外設計五個實驗(觀察及操作實驗)，結合DNA 分子遺傳標記技術，分別深入探討艾氏樹蛙兩種群體生殖的形成、機制及功能。艾氏樹蛙在生殖時期會出現兩種不同群體生殖的現象，第一種是兩批卵先後產在竹壁上，之後蝌蚪共存於水池，野外發生率為5%; 第二種是水池有一批蝌蚪(約3-4 週大)時，另一批卵被產在竹筒內壁上，形成兩批不同時期的子代共存於同一個竹筒中，其野外發生率為40%。第一年利用野外實驗，檢測第一種群體生殖對卵存活及孵化率的影響，來探討和低發生率(5%)的關係; 同時檢測是否真菌為密度制約死亡 (density-dependent mortality)之主因。接著，利用分生標記分析兩批卵是否為護卵雄蛙所產，以確認第一種群體生殖是副產品機制(by-product approach)所造成的可能性。然後再探討利用這種群體生殖策略的個體是否和親子關係不確性 (uncertainty of paternity)有關。第二及三年在竹林添加有水竹筒或製作成對 (有或無蝌蚪)的有水竹筒，探討第二種群體生殖是否為適應機制(adaptive approach)所造成。接著探討群體生殖是否對卵的存活、孵化率及蝌蚪的存活、變態率有正面的影響，從而推測形成的可能機制。本計畫是第一個去探討具有親代撫育蛙類群體生殖現象的研究。在實驗過程充分利用艾氏樹蛙特殊生殖習性和竹筒可以容易被操作的優點，檢測群體生殖的相關理論，並配合利用分子生物標記，提出新的假說去探討群體生殖形成的機制及和親代撫育相互影響的關係，預期研究成果對群體生殖領域提供不同生活史特徵物種的比較之用外，也對相關議題的研究有重要的貢獻。 Communal breeding is a common phenonemon that taxonomically widespreads among animals. To date, there are two approaches (adaptive or by-product) to explain the types and functions of communal breeding, within which many hypotheses have been postulated. However, the adaptive value of this behavior in the vast majority of cases (except for mammals and birds) remains unclear and to be evaluated. Here I propose a three-year project in which I will design five experiments (observational and manipulated studies), coupled with genetic analyses using molecular markders, to study the formation, mechanisms, and function of communal breeding of Kurixalus eiffingeri. Kurixalus eiffingeri has two types of communal breeding: one is when an egg clutch is laid in a egg-occupied stump, and two clutches hatch simultaneously; whereas the other is when an egg clutch is laid in a tadpole-occupied stump where tadpoles are 3-4 weeks old. The occurrence rate of these communal breeding is 5 and 40%, respectively. In the first year, I will study the survival and hatching rate of eggs in communal nests in relation to low occurrence rate. I will also evaluate whether the fungal infection explains the density–dependent mortality of eggs in communal nests. In addition, I will analyze the genetic relationship between double clutches and attending male to assess whether this communal breeding can be explained by the by-product approach which relates to the uncertainty of paternity of attending males. In the second and third years, I will use manipulated studies (stump supplementation and stump-pairing setting) to assess whether the second type of communal breeding can be explained by the adaptive approach and has beneficial effects on the egg survival and hatching and tadpole survival and metamorphic rate. These results will be helpful to unveil the possible casual mechanisms of communal breeding. This proposed project is the first to study the communal breeding of frogs with parental care. Using the unique features of reproductive behavior of K. eiffingeri and the manipulability of bamboo stumps, coupled with molecular markers, I could not only test many hypotheses that have been proposed to explain the occurrence of communal breeding in K. eiffingeri, but also postulate new hypotheses that derived from the my results. I expect the results of this study could provide critical information on the communal breeding with different life history attributes and make important contribution to the general understanding of communal breeding.
