Ecological factors promoting biodiversity in Lakes BBTM

比瓦湖、贝加尔湖、坦噶尼喀湖和马拉维湖分别是独特的淡水环境，拥有丰富的特有物种。在这些湖泊中，坦噶尼喀湖已知多种物种间的合作关系，这种合作关系可能有助于维持栖息地的高生物多样性，这种合作关系在其他高生物多样性的古湖泊中也存在。为了证实这一假设，在贝加尔湖、坦噶尼喀湖和马拉维进行了实地观察。在坦噶尼喀湖，各种慈鲷的种间合作关系越来越多，尤其是为了避免食鳞鱼和食鱼鱼的伤害。马拉维湖和坦噶尼喀湖拥有丰富的丽鱼动物群，这两个湖的鱼类群落在功能组成上是相似的。然而，在马拉维湖，鱼类似乎表现出微弱的种间关系，特别是在合作觅食和合作防御鱼食动物和咬鳍者的观点上。贝加尔湖和琵琶湖的鱼类群落较为简单，没有明显的种间合作关系。因此，后两个湖泊鱼类群落的生物多样性可能主要是通过资源分配的种间关系来维持的。坦噶尼喀湖鱼类群落的生物多样性不仅通过物种间资源分配维持，还通过多种种间合作关系维持。在这一观点下，马拉维湖的情况尚不清楚，需要对马拉维湖进行更详细的调查，以开展古湖泊生物多样性的比较研究。

Lakes Biwa, Baikal, Tanganyika and Malawi are unique freshwater environments with rich endemic species, respectively. Among these lakes, various kinds of cooperative relationship between species are known from Lake Tanganyika, which might promote to maintain a high biodiversity in a habitat, and such interspecific relationship is plausible in other ancient lakes with a high biodiversity. To ascertain this hypothesis, field observations in Lakes Baikal, Tanganyika and Malawi were conducted.In Lake Tanganyika, more and more various cooperative interspecific relationships among cichlid fishes have been found, especially to avoid the harm from scale-eating fishes and piscivorous fishes. Lake Malawi holds a rich cichlid fauna as well as Lake Tanganyika, and the fish communities of these two lakes are similar in their functional composition. In Lake Malawi, however, the fishes seem to show weak interspecific relationship especially in the views of cooperative foraging and cooperative defense against piscivores and fin-biters.In Lakes Baikal and Biwa, the fish communities are more simple without notable cooperative interspecific relationship. Therefore the biodiversity in fish communities in latter two lakes are, probably, maintained mainly by the interspecific relationship of resource partitioning. In contrast, the biodiversity in fish community in Lake Tanganyika is maintained not only by resource partitioning among species but also by various kinds of cooperative interspecific relationship. The case of Lake Malawi is unclear in this view point, and more detailed survey in Lake Malawi is necessarry to develope the comparative study of biodiversities in ancient lakes.