Pfingstl Tobias, Baumann Julia
Institute of Zoology, University of Graz, Universitaetsplatz 2, 8010, Graz, Austria.
Exp Appl Acarol. 2017 Jun;72(2):115-131. doi: 10.1007/s10493-017-0149-3. Epub 2017 Jun 20.
The intertidal oribatid mite species Alismobates galapagoensis and Litoribates caelestis occur on the archipelago of Galápagos. To test for morphological variation between populations of different islands, a comprehensive morphometric study was performed. Four A. galapagoensis populations from the islands Bartolomé, Isabela, Santa Cruz and San Cristobal, as well as two L. caelestis populations from Bartolomé and Santa Cruz were investigated. The L. caelestis populations did not show any significant differences whereas the A. galapagoensis populations exhibited clear divergences indicating speciation. Differences in overall size of A. galapagoensis apparently followed a gradient from East to West, with specimens from San Cristóbal being the largest and individuals from Bartolomé and Isabela being the smallest. Apart from size, significant shape differences were found in the epimeral region and females showed stronger variation among islands than males. The degree of morphological divergence seems to correlate with geographic distance, i.e. populations from islands located closer to each other showed fewer differences than populations from distant islands. Based on this correlation we suggest that transport between islands has happened mainly by drifting on ocean currents.
潮间带甲螨物种加拉帕戈斯阿利氏甲螨（Alismobates galapagoensis）和天体滨甲螨（Litoribates caelestis）分布于加拉帕戈斯群岛。为了测试不同岛屿种群之间的形态差异，开展了一项全面的形态测量学研究。对来自巴托洛梅岛、伊莎贝拉岛、圣克鲁斯岛和圣克里斯托瓦尔岛的四个加拉帕戈斯阿利氏甲螨种群，以及来自巴托洛梅岛和圣克鲁斯岛的两个天体滨甲螨种群进行了调查。天体滨甲螨种群未显示出任何显著差异，而加拉帕戈斯阿利氏甲螨种群则表现出明显的差异，表明存在物种形成。加拉帕戈斯阿利氏甲螨的整体大小差异显然呈现出从东到西的梯度变化，圣克里斯托瓦尔岛的标本最大，而巴托洛梅岛和伊莎贝拉岛的个体最小。除了大小之外，在腹节区域发现了显著的形状差异，并且雌性在岛屿之间的变异比雄性更强。形态差异程度似乎与地理距离相关，即来自彼此距离较近岛屿的种群比来自遥远岛屿的种群差异更小。基于这种相关性，我们认为岛屿之间的迁移主要是通过洋流漂流发生的。
