海藻群落における遷移のメカニズム

概要

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Early successional species (ESS) occupy most open spaces on rocky shores due to the abundance of their reproductive cells in the water. Late successional species (LSS) also invade these open spaces but occupy a smaller space because of the small number of their reproductive cells in the water. Within a few days, however, most of the settled reproductive cells and their germlings are lost, and ESS occupy most of the open space. There is little evidence that ESS modify the environment or inhibit the invasion of LSS. In most cases, ESS exist alternately with LSS. In some places, this alternation of species does not occur and ESS dominance continues.A model of this system has been proposed. The “survival rate model” suggests that the mortality and the ratio of reproductive cells of both species governs whether the alternation from ESS to LSS occurs or not. We show that the relationship between the ratio of reproductive cells of LSS to ESS, r, and the ratio of mortality of LSS to ESS, m, is very important for determination of succession in algal community. If ESS occupy 1/(r+1) of area, when more open space becomes available, ESS will occupy m/(r+m) of that new area. When r is constant and m becomes smaller, the spece occupied by ESS becomes smaller. So succession occurs when m is larger than 10-1×r. However, when the mortality rates of ESS decrease and the value of m is r or more, ESS are dominant.
社団法人日本水産学会の論文