Germination patterns in three terrestrial orchids relate to abundance of mycorrhizal fungi

Abstract

Summary The spatial distribution of plants, which is often generated by patterns of seed recruitment, is an important determinant of population dynamics, especially for orchids with seeds that must be exposed to appropriate mycorrhizal fungi. We compared the distribution and abundance of target mycorrhizal fungi detected in the soil using DNA‐based molecular techniques and germination in seed packets of Goodyera pubescens, Liparis liliifolia and Tipularia discolor. We further examined Tulasnella spp. associated with G. pubescens to determine whether areas with abundant host fungi resulted from multiple genets of the same species or from a single widespread fungal genet. We found that target fungi were more likely to be detected using soil DNA assays than by seed germination. Based on soil DNA, fungi were more widespread than suggested by seed germination, which most often reflected the presence of abundant mycorrhizal fungi in the soil. Fungi were more likely to be abundant close to established orchids. Established plants of G. pubescens that were < 50 cm apart associated with a single abundant fungal genet, while those > 50 cm apart associated with multiple fungal genets. Synthesis. This study demonstrates the importance of using multiple methods to detect the distribution and abundance of target fungi and suggests that fungal ‘hot spots’ may be keys to the dynamics of orchid populations.