Ecological factors promoting biodiversity in Lakes BBTM

琵琶湖、贝加尔湖、坦噶尼喀湖和马拉维湖是独特的淡水环境，分别拥有丰富的地方物种。在这些湖泊中，物种之间的各种合作关系是已知的坦噶尼喀湖，这可能会促进维持一个栖息地的高生物多样性，这种种间关系是可能的，在其他古老的湖泊与高生物多样性。通过对贝加尔湖、坦噶尼喀湖和马拉维湖的实地观察，发现坦噶尼喀湖慈鲷科鱼类之间存在着越来越多的种间合作关系，特别是为了避免鳞食性鱼类和食鱼性鱼类的危害。马拉维湖和坦噶尼喀湖拥有丰富的慈鲷动物群，这两个湖泊的鱼类群落在功能组成上相似。马拉维湖鱼类群落的种间关系较弱，尤其是在合作觅食和合作防御鱼类和咬鳍类方面，贝加尔湖和琵琶湖鱼类群落结构较为简单，种间关系不明显。因此，后两湖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。与此相反，坦噶尼喀湖鱼类群落的生物多样性不仅是通过物种间的资源分配来维持的，而且还通过各种合作的种间关系来维持。马拉维湖的情况在这一观点上是不清楚的，需要在马拉维湖进行更详细的调查，以开展古代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.