艾氏樹蛙雄性親代撫育行為及生殖策略之研究

Abstract

本論文研究主題是艾氏樹蛙雄蛙親代護卵的行為生態及護卵期間的雄蛙生殖策略之研究。護卵行為是指親代在產完卵後，一段時間內會駐留於卵塊附近的行為，艾氏樹蛙的護卵工作皆是由雄蛙執行。根據野外觀察資料顯示，在有卵的竹筒中，護卵的頻率約27%。雄蛙夜間護卵頻率(約35%)較白天頻率(約20%)高。此外，護卵頻率隨卵的發育期越後期而顯著降低，但與卵數則沒有顯著相關。雄蛙在竹筒護卵期間，有1/3的時間在執行以腹部主動濕潤卵的行為，推測與防止卵乾燥有關。但雄蛙護卵頻率與卵最後的孵化率沒有顯著相關，推測可能其他生態因子，如：氣候及微棲地的環境因子對孵化率也有影響。而護卵頻率的估算也可能有誤差，因此，關於雄蛙護卵功能的探討需要進一步的實驗證實。 在艾氏樹蛙夜間活動觀察中，發現有雄蛙在護卵的同時一邊鳴叫吸引雌蛙，且在同一個竹筒獲得第二窩的卵。對雄蛙來說，邊護卵邊鳴叫應該可以降低因為執行親代撫育而降低交配機會的損失。然而，相較於沒有護卵的雄蛙，絕大多數艾氏樹蛙雄蛙在護卵在期間，會明顯降低鳴叫頻率。而野外也只有發現3.9%的竹筒會有兩窩不同時期的卵。因此，大多數艾氏樹蛙雄蛙並不會採用在護卵並同時鳴叫以吸引配偶的生殖策略。我們利用微隨體為分子遺傳標記，檢測三個竹筒中，護卵雄蛙與兩窩不同發育期的卵之親子關係。其中兩個竹筒的結果顯示，兩窩不同發育期的卵之父親皆是護卵的雄蛙，但應是屬於不同雌蛙的後代。其中一個竹筒的結果則發現，護卵的雄蛙是後產卵的那窩的卵之父親，但較早產卵的那一窩，有部分卵是不屬於護卵的雄蛙的子代，而兩窩卵也應是屬於不同雌蛙的後代。這樣的結果顯示雄蛙在護卵的同時鳴叫，應是吸引到不同的雌蛙在同一竹筒產卵。雄蛙這樣的生殖策略，可能會造成有兩個雌蛙餵食同一竹筒的蝌蚪之親代照顧。而同一發育期的卵不屬於一個父親的子代，則推測可能是一雌多雄的假交配型式造成。由於本論文中微隨體的解析力尚有不足，因此，需要進一步的遺傳分析來確認親子關係。

The objective of this dissertation was to assess the parental care and reproductive strategy in male Chirixalus eiffingeri (Anura: Rhacophoridae). Combining field observations and genetic analyses, I studied the behavioral pattern of egg attendance and the reproductive strategy of male C. eiffingei while attending egg clutches. Egg attendance in C. eiffingeri was exclusively performed by males and the attendant frequency was 27%. Attendant frequency followed a distinct diel pattern that male attended clutches more at night than in the daytime. Furthermore, attendant frequency decreased with developmental stages of embryos, suggesting that the male attending behavior played a crucial role for early development of the embryos. Field observations confirmed that male frogs actively moisturized egg clutches using the abdominal region, and this presumably is to prevent desiccation of egg clutches. The lack of significant relationship between hatching rate and frequency of egg attendance suggests that embryonic survival of C. eiffingeri is more than a function of egg attendance, and some factors such as climate and characteristics of microhabitats, may also influence the survivorship of embryos. Most male C. eiffingeri substantially reduced the frequency of calling while egg attending. A low frequency of bamboo stumps containing multiple clutches found in the field suggests that continuing calling during egg attendance is not routinely adopted by male frogs. However, some attending males did obtain another mating during egg attendance through continuous calling which resulted in multiple clutches. The results from two cases suggest that the two egg clutches in the same bamboo stump were sired by the attending male with two different females, but in one case where two egg clutches in a bamboo stump were most likely sired by at least two male (including attending male) with two different females. These results suggest a possibility of complicated interactions between the two females and offspring.