斯文豪氏攀蜥與黃口攀蜥間型態與資源分配之研究

Abstract

論文的第一部份採用單變數以及多變數的統計方法來檢驗斯文豪氏攀蜥與黃口攀蜥的雌雄兩性在下列身體部位上絕對以及相對長度的差異：體長、尾長、頭長、頭寬、前肢長、後肢長、最長指長以及最長趾長。結果顯示，雄性斯文豪氏攀蜥在所有身體部位的絕對長度皆較雌蜥為長，但將體型大小的效應排除之後，發現雄蜥的頭長與頭寬在比例上較雌蜥為長，但體長以及四肢長度卻皆較雌蜥短。黃口攀蜥的雌蜥與雄蜥則只在最長指與最長趾的絕對長度上有顯著差異，雄蜥的手指較長，而雌蜥的腳趾較長。去除體型的影響之後，黃口攀蜥雄蜥仍然具有相對較長的手指，但雌蜥除了具有相對較長的腳趾外，也具有相對較長的體長。在兩物種之中，某些身體部位相對長度的差異是來自於雌雄個體在該部位發育上的速度不同，而另一些身體部位相對長度的差異卻是因為初始比例就不相同，而這種初始比例上的差異又被相同的成長速度給保留了下來。斯文豪氏攀蜥的雌雄二形性可以被性擇以及天擇解釋。雄蜥演化出在比例上較大的頭，可能是因為這個特徵能夠增進雄蜥的打鬥能力，因而對領域的防衛與取得產生貢獻；雌雄兩性在四肢比例上的差異無法被停棲環境上的差異所解釋，我們猜測四肢比例上的差異會造成雌雄兩性在避敵行為上有差異；雌蜥在比例上較長的身體則可能是為了容納體內的卵而演化出的特徵。 論文的第二部分探討兩物種間的資源分配以及兩組生態與形態間的關係：相對四肢長度與停棲環境、頭部尺寸與獵物尺寸。相對四肢長度與停棲環境間的對應僅在黃口攀蜥種內獲得支持： 黃口攀蜥的雌性與雄性在停棲高度與停棲表面寬度上沒有顯著差異，其相對四肢長度也沒有差異，與理論預測相符。雄性斯文豪氏攀蜥停棲高度較雌性為高，利用的停棲表面較寬，但其相對四肢長度卻較雌蜥為短。相對四肢長度與停棲環境的對應關係在種間比較時消失了，推測可能是因為斯文豪氏攀蜥頭部較大，因此四肢必須相對縮短以使重心貼近能夠貼近停棲表面，增加穩定性。頭部尺寸與獵物尺寸的對應關係部論在種內或種間都沒有獲得支持。雖然頭部尺寸有顯著差異，食性重疊度卻非常高。雄性斯文豪氏攀蜥與黃口攀蜥在日活動週期、停棲環境、以及食性方面非常類似。且根據野外觀察，打鬥行為在野外較常發生在不同種的雄性個體之間。因此我們推論兩物種在實驗樣區內可能在領域上發生競爭。我們需要更進一步的研究，例如比較共域與非共域族群之型態與資源利用、在共域族群中移除其中一物種與在非共域族群中加入另一物種，並觀察後續變化等，以徹底釐清兩物種在生態上的關係。

The first part of this thesis describes sexual dimorphism in size and shape in two Japalura lizards, J. swinhonis and J. polygonata xanthostoma. Univariate and multivariate statistics were applied to test interesexual differences in size and shape of the following body parts: body length, tail length, head width, head length, forelimb length, hindlimb length, length of the longest finger, and length of the longest toe. The results showed that male J. swinhonis were larger in size of all body parts. After the effect of body size was accounted for, males had proportionately longer and wider heads, shorter body lengths and limbs. Male and female J. polygonata xanthostoma, on the other hand, differed only in the size of the longest finger and toe, with males larger in finger length and females larger in toe length. After the effect of body size was accounted for, males still had longer fingers, and females had longer toes and body lengths. Via the examination of allometric patterns of both species, shape dimorphism was found to result either from different growths trajectories or an initial difference in proportion maintained by identical growth patterns between the two sexes. Sexual dimorphism in J. swinhonis could be explained in the context of sexual and natural selection. Prominent heads of male lizards were likely to be the consequence of sexual selection to enhance fighting ability, and longer bodies of females might evolve for accommodation of eggs. Sexual dimorphism in limb shape suggests that the two sexes might have different behavioral response to predators. The second part of this thesis investigates resource partitioning between the two species and two ecomorphological relationships: relative limb lengths vs. perch habitat and head size vs. diet. The correspondence between relative limb lengths and perch habitat was only found intraspecifically in J. polygonata xanthostoma: males and females did not differ in perch habitat and relative limb lengths. The matching between relative limb lengths and perch habitat disappeared interspecifcally, which may be explained by biomechanics. The correspondence between head size and diet was not found both intra- and interspecifically. Feeding niche overlap was high between male and female J. swinhonis and J. polygonata xanthostoma despite significant differences in head sizes. The similarity of perch habitat, diet, and daily activity patterns between male J. swinhonis and J. polygonata xanthostoma, with the fact that antagonistic behaviors were observed more often between heterospecific males, suggested that males of the two species might compete over territories. To clarify their ecological relationships, comparisons of morphology and resource use between different populations, and experimental manipulations involving addition and removal in either allopatric or sympatric populations are required as the next steps.