Mycorrhizal Status of Obligate and Facultative Epiphytic Ferns in a Valdivian Temperate Forest of Patagonia, Argentina

Abstract

Arbuscular mycorrhizae (AM) influence the growth, morphology and fitness of the plant species they colonize. Despite the abundance and importance of epiphytes in forest dynamics, little is known about AM in these plants. Abundant epiphytes are present in the Valdivian temperate forests of South America, where ferns are one of the most important components of the epiphytic vascular flora. The aim of this work was to analyze the occurrence of AM in sporophytes of obligate and facultative epiphytic fern species in a Valdivian temperate forest of Patagonia, Argentina. We examined the roots of 10 epiphytic fern species. Roots of 66 sporophytes were collected from tree trunks and branches between 0.5 and 2 m height above the ground and were stained by using a modified Phillips and Hayman (1970) method. Of the 10 species examined in the present study two were found to be obligate epiphytes, six were facultative epiphytes and two could not be classified because few individuals were found. Most of them lacked AM structures, except for seven Hymenophyllum sporophytes which were rooted in soil and possessed scarce knobby hyphae and structures similar to coils and vesicles. Abundant dark septate fungi were observed within the cortex of all samples. The absence of AM in epiphytes may be explained by different ecological or taxonomic reasons, but in this study we suggest that root morphology may be an important factor influencing mycorrhizal behavior in ferns.