Numerical analysis on the dynamics of communities for sessile colonial animals

通过模拟聚集性苔藓动物的生态，对空间竞争进行了定量估计，并构建了空间竞争模型。起初，硬底上没有苔藓虫。苔藓虫的幼虫每天以相同的数量随机定居在底部。幼虫很快就会长成动物园。根据物种和大小，动物园的数量会随着时间的推移而增加。这团状的动物被称为蚁群。当动物园相互接触时，就会发生空间竞争。竞争表现为一只动物园比另一只动物园过度生长。在这种情况下，我假设过度生长的极限值由物种对和两个物种的大小比例表示。当大小比大于极限值时，一个物种的生长超过其他物种。过度生长的动物会被杀死，而这一物种就会占据过度生长的区域。空间继续随着时间的推移而填满，并达到完全覆盖的区域。模拟在此状态下完成。结果表明：尽管种群参数和竞争参数是相同的，但由于幼虫随机落底，模拟实验之间的差异较大。这意味着，如果重复数很少，则可能出现与真实结果相反的结果。在对峙系统中，两个物种的盖度平均相等，在平赢系统中也是如此。但在对峙系统中，盖度的变化比均匀输赢系统中的小。竞争物种的覆盖度在极限值的1处发生灾难性的变化。即使是弱物种也占据了相当大的空间，如果有强物种以弱物种抑制竞争物种，如所描述的间接影响。物种数从3增加到10，物种盖度的相对差异有减小的趋势。

I estimated quantitatively space competition of which model was constructed by simulating the ecology of encrusting colonial bryozoans. At first, there is no bryozoa on the hard bottom. Larva of bryozoans settle randomly by the same number on the bottom every day. The larva grow to zooids soon. Zooids increase in their numbers with time according to the species and the size. The clump of zooid is called as the colony. When zooids contact each other, the space competition occurs. The competition expressed as over-growth of one zooid over the other zooid. In this case, I postulate the limiting value of over-growth which is expressed by the species pair and the size ratio of two species. When the size ratio becomes larger than the limiting value, the one species grows over the other species. Over-grown zooids are killed and the one species occupy thus over-grown area. The space continues to fill with time and reached to completely covered area. The simulation finishes in this state. The results were as follows :There is fairly large variation between simulation experiments owing to random settling of larva to bottom, even though population parameters and competition parameters are the same pattern. This means that if the number of repeats is small, the contrary result to true one is possible.The covers of two species in stand-off system are equal in average, and the same is true in even win-loss system.However, the variation of covers is smaller in the stand-off system than in even win-loss system.The coverage of competing species change catastrophically on 1 of the limiting value.Even weak species occupy fairly large space, if there is strong species which suppress the competing species with weak one, as described as the indirect effect.Increasing in species number from 3 to 10, there is a trend that the relative difference in covers of species decreases.