以物種分布模式預測台灣北部兩種攀蜥的共域區並檢視形態置換現象

Abstract

形態置換假說：當形態相似的物種共存於同一群聚時，同一物種於共域區的族群會在一個或多個形態上產生分化。透過形態上差異的增加，可降低對於限制性資源的種間競爭強度。斯文豪氏攀蜥(Japalura swinhonis)與黃口攀蜥(Japalura polygonata xanthostoma)皆有分布在台灣北部地區。這兩個同屬種有相似的外觀型值與生態習性，但在巨觀棲地上有所差異。我使用兩物種在巨觀棲地上有所差異的變數建構各物種的分布模式，預測兩物種的潛在共域區，並由潛在共域區的資訊選擇樣區檢視兩物種的形態置換現象。物種分布模式的結果顯示對這兩個物種出現機率影響最大的兩項因子分別是到人為土地利用密集區的距離以及森林面積，同時預測的結果讓我得以確認四個共域區作為後續檢視形態置換現象之用。對相同物種而言，四個共域區中有三個發現其與鄰近的非共域區在頭部相關的外觀型值顯著的變小。分析結果也發現對共域區內的族群而言，與咬合力有關的外觀型值在確實有發現明顯的形態置換現象；但與最大衝刺速度較有相關的外觀型值在共域區的種間差異反而降低了。形態置換現象可能同時受到種間競爭與天敵捕食壓力的影響，因而降低兩物種在共域區的種間差異。

Character displacement hypothesis states: when species with character similarity coexist in the same community, the population in sympatric location would displace in one or more characters. The increased differences in character space would reduce the strength of inter-specific competition for limited resources. Both Japalura swinhonis and Japalura polygonata xanthostoma occur in northern Taiwan. The two congeners have similar morphology and ecology, yet different macro-habitats. I applied species distribution model to identify environmental features that describe their differences in macrohabitat use, and predict the potential contact zone of the two species. Then use the latter to examine the pattern of character displacement. The results of species distribution modeling showed the distance to human-use area and total area of forest contribute the most to the distribution of the two species. The models allowed me to successfully locate four main regions of species coexistence. I found evidence for character displacement in most sympatric locations of Japalura swinhonis and Japalura polygonata xanthostoma. In four of the sympatric locations I surveyed, three of them showed significant intra-specific differences in their morphology between sympatric and allopatric locations. The head related parameters were consistently smaller for both species. While inter-specific difference of bite force related characters were greater in the sympatric than allopatric locations, characters related to sprint speed were more similar in the sympatric locations. Character displacement may be effect by inter-specific competition and predation risk in sympatric location, therefore, the characters related to sprint speed would be more similar.