日本樹蛙鳴叫特徵和外部形態特徵的地理變異

Abstract

日本樹蛙（Buergeria japonica）廣泛分布在琉球群島和台灣，為橫跨不同島系之間的兩棲動物，模式標本產於琉球群島北部的奄美大島。近年研究指出，日本樹蛙族群在島間具有高度的分化，且台灣島內也並非單系群，顯示日本樹蛙族群的分類地位有重新檢視的必要。聲音及外部形態是蛙類繁殖與物種辨識重要的依據，因此本研究利用這兩組特徵進行日本樹蛙族群間地理變異的檢測。總共分析來自琉球群島和台灣，共17個族群的宣示叫聲以及13個族群的外部形態特徵。使用卡方檢測和廣義線性混合模型（GLMM）檢測鳴叫聲在地區間的差異，並使用主成份分析濃縮19個外部形態特徵，接著根據過去利用遺傳訊息建立的親緣關係樹進行判別分析，尋找最佳的分群方式，並根據分群結果利用GLMM進行不同單系群間的差異性檢測。結果顯示，日本樹蛙的叫聲由短鳴叫和長鳴叫所組成。台灣東部和西南地區具有一種其他地區未曾記錄到的長鳴叫類型；而這些族群短鳴叫的鳴叫時間和鳴叫分貝上升時間也比其他地區短促。另外，台灣西北地區的主頻率則比其他地區來的高。利用形態特徵進行判別分析的結果也顯示，分群為台灣東部和西南地區（台灣群），和琉球群島及台灣西北地區（日本群）兩個單系群時具有最佳的判別正確率，且台灣群在頭部特徵上顯著的大於日本群。綜合以上結果和前人的遺傳訊息，皆顯示日本樹蛙有一個形態不易辨識，但叫聲明顯分化的隱蔽種存在。

Delimitating species is a central concern in evolutionary biology, taxonomy, and biological conservation. Acoustic and morphological traits play key roles in frogs, especially in species recognition and reproduction. Buergeria japonica is widely distributed from Ryukyu Archipelago to Taiwan. Recent studies indicated the extremely high genetic differentiation with non-monophyletic relationship among populations in Taiwan, which revealed the necessity to reevaluate the taxonomic status of this species across their distributional range. In this study, we sampled advertisement calls from 17 localities and morphology from 13 localities across Ryukyu and Taiwan to examine the variation among populations. By analyzing their advertisement calls, we found an exclusively unique type of long call occurring in the southwestern and eastern populations in Taiwan. Moreover, these populations also represent faster call duration and shorter call rise time compared to those from the other regions. On the other hand, the dominant frequency in the northwestern populations in Taiwan was higher than the others. Morphological measurements with discriminant analysis indicated that the species should be separated into two forms, which correspond to Taiwanese clade (the southwestern and eastern populations in Taiwan) and Japanese clade (Ryukyu and the northwestern populations in Taiwan) defined by mitochondrial sequences. Principal component analysis showed that traits on the head from Taiwanese clade are significantly higher than the other. These results indicated that there is a cryptic species in Taiwan, which represents different acoustic signal but with similar morphology from B. japonica sensu stricto.