Ecology: Biology of Interaction. IV-14. Amensalism and Neutralism

IV-14. Amensalism and Neutralism Amensalism, or a relationship in which one population experiences an unfavorable influence from another, while the other is unaffected by it, is an extreme case of competition. Such relationships arise when one of the competitors turns out to be significantly stronger than the other. A large tree shades the grass at its base, hardly feeling the adverse effects of this grass. A phenomenon called "red tide" is common in tropical oceans. Dinoflagellates (Dinoflagellata), planktonic armored flagellate single-celled organisms, accumulate a toxin that suppresses competitors and protects them from predators. When these algae become numerous, the water turns red and becomes dangerous for most living organisms, including fish and benthic fauna. We mentioned that one type of population relationship is neutralism – relationships in which populations do not affect each other. This means that the two populations seem not to exist for each other. Can such a phenomenon occur when we are talking about two populations inhabiting the same ecosystem at all? Strictly speaking, no. Every organism consumes resources, dissipates energy, changes the environment, and thus, at least to a small extent, affects all organisms living with it. However, this influence can be very small – below a certain threshold, after which it is not worth considering. In view of this, neutralism is not the absence of influence between two populations, but a situation where this influence can be neglected. And in what case will the interaction between two populations within the same ecosystem be minimal? When there are no direct links between populations, when they belong to different food chains, each of which is well-regulated. Probably, the centipede Geophilus (Geophilomorpha sp.), which feeds on small invertebrates in the detritus food chain, and the forest dormouse (Dryomys nitedula), which feeds on fruits and insects in the tree canopy, have very little effect on each other (Fig. IV-14.1). Fig. IV-14.1. Do the dormouse and the geophilid affect each other? They do, as they participate in the matter cycle in the ecosystem, somehow change plant productivity, etc. But when studying this ecosystem, the influence of these animals on each other can be neglected.