兩群落的比較在生態上是一個常見的問題，想要了解其不同之處，利用指標來探討兩群落之相似度是方法之一，Morisita指標即為一量度兩群落相似程度的指標。過去討論相似度之範圍僅限於兩個群落，本文將此相似性指標推廣至三個群落，提出了兩個新的指標值及其估計量，使Morisita指標可以應用的範圍更為寬廣。
文中先回顧了幾種常見的相似性指標之發展，包括Jaccard指標、Sørensen指標、Lennon指標以及Morisita指標，再呈現將Morisita指標推廣後之新指標及其所衍生的兩個估計量，分別為漸近不偏估計量與最大概似估計量，推導出估計量之偏誤情形，並嘗試用三種方法-拔靴重抽法、漸近近似法與摺刀法來估計其估計量之變異程度。
為了解其估計結果，本文模擬了在改變樣本數大小以及共同種類數的情況下，觀察此兩種指標之估計量的表現情形，並建議在不同情形下所適用估計量，最後將此結果應用在實例上。

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