Dean W R J, Bond W J
FitzPatrick Institute, University of Cape Town, 7700, Rondebosch, South Africa.
Botany Department, University of Cape Town, 7700, Rondebosch, South Africa.
Oecologia. 1990 Jun;83(3):388-391. doi: 10.1007/BF00317565.
Few studies of island biogeography have been made on islands in which the time of insularization is precisely known. We tested the effects of island formation on ant species diversity in a man-made lake in South Africa, to determine whether island effects are detectable after only 16 years of insularization. The number of ant species observed at trap-line censuses on islands was significantly correlated with island size (r=0.608; P<0.05) and ant species diversity was generally low compared with similar mainland habitats. Mean species number for all islands, including landbridge islands, was 5.5±3.3 species, and on mainland sites was 7.9±2.85 species. Island effects were more marked on islands <20 ha, which had a mean of 3.3±2.5 species per island. Species number on islands was inversely related to densities of the aggressive Anoplolepis custodiens and A. steingroeveri. These two species were only patchily distributed on mainlands, but these ants were nearly ubiquitous on small islands. Several lines of evidence suggest that this single species domination may be responsible for island effects. Island sites also differed in the number of ant species in different trophic groupings, tending to have fewer granivorous species than the mainland sites, but species in other diet groups were similar in both island and mainland habitats. We conclude that there have been marked changes in the ant faunas on islands smaller than 20 ha apparently due to changes in abundance of the dominant ant species. However, the causes of these changes are unknown.
很少有关于岛屿生物地理学的研究是在岛屿形成时间精确已知的岛屿上进行的。我们在南非的一个人工湖中测试了岛屿形成对蚂蚁物种多样性的影响，以确定在岛屿形成仅16年后是否能检测到岛屿效应。在岛屿上的陷阱线普查中观察到的蚂蚁物种数量与岛屿面积显著相关（r = 0.608；P < 0.05），并且与类似的大陆栖息地相比，蚂蚁物种多样性总体较低。包括陆桥岛在内的所有岛屿的平均物种数为5.5±3.3种，而大陆地点的平均物种数为7.9±2.85种。岛屿效应在面积小于20公顷的岛屿上更为明显，这些岛屿每个岛屿平均有3.3±2.5种蚂蚁。岛屿上的物种数量与具有攻击性的卡氏织叶蚁和斯氏织叶蚁的密度呈负相关。这两个物种在大陆上只是零星分布，但在小岛上这些蚂蚁几乎无处不在。几条证据表明，这种单一物种的主导地位可能是造成岛屿效应的原因。岛屿地点不同营养类群中的蚂蚁物种数量也有所不同，与大陆地点相比，食谷物种往往较少，但岛屿和大陆栖息地中其他食性类群的物种相似。我们得出结论，显然由于优势蚂蚁物种数量的变化，面积小于20公顷的岛屿上的蚂蚁动物群发生了显著变化。然而，这些变化的原因尚不清楚。
