Which is not true regarding keystone species?

A. Keystone species can be mutualists with other species.
B. Keystone species are often rare individuals in a community.
C. Keystone species are most likely to be commensalists.
D. Keystone species can be highly lethal to several species in a community.
E. Keystone species may interact with only a single other species.

The correct option is (c), which is (keystone species are most likely to be commensalists). Statement (c) Keystone species are most likely to be commensalists is not true regarding keystone species, as their roles are dynamic and significant within ecosystems, unlike the suggestions in this statement.

Explanation:

The correct option is (c), which is (keystone species are most likely to be commensalists). The statement that is not true regarding keystone species is (c) Keystone species are most likely to be commensalists. The term keystone species is used to describe a species whose effect on its ecological community or ecosystem is disproportionately large compared to its abundance.

An example is Pisaster ochraceus, the intertidal sea star, which has a significant impact on mussel populations and thereby affects the entire community structure and biodiversity.

Keystone species can have various roles, including mutualists, predators, or herbivores, but saying that they are'most likely' to be commensalists does not accurately reflect their dynamic roles within ecosystems.

In contrast, there are examples of keystone species, like the banded tetra, that contribute essential nutrients to their ecosystems, highlighting their influential ecological roles.