Introduction

Abstract

In cases of moderate temperature and sufficient rainfall, Earth’s land areas are green due to coverage by forests. A forest is composed of varied plant species and provides diverse microhabitats for various animals and fungi. Each plant species harbors a specific insect fauna on its leaves and a specific fungal flora on its roots. Moreover, the biodiversity of a forest is determined by the diversity of associations in which plants participate. A rare mycoheterotrophic plant growing in a sacred place in a pristine forest, for example, is simultaneously a symbol of the plant diversity therein and of the complexity of the underground network of plant roots and mycorrhizal fungi. When two organisms intimately interact, the interaction occasionally becomes mutual through evolution even if the interaction is initially antagonistic.