Mycorrhizae in Hawaiian Pteridophytes: Occurrence and Evolutionary Significance

Forty‐five percent of the Hawaiian pteridophyte flora were examined for mycorrhizae. Vesicular‐arbuscular mycorrhizae were present in 66 of the 89 species examined. Nonmycotrophy was significantly higher in Hawaiian pteridophytes than in non‐Hawaiian pteridophytes. The highest mycorrhizal colonization occurred in the leptosporangiate families Dicksoniaceae, Dryopteridaceae, and Lindsaeaceae. Mycotrophy was lower in the eusporangiate families. Substrate strongly influenced the presence of mycotrophy. Mycorrhizae were present in 83% of terricolous species, in 86% of epilithic species, in 55% of epiphytic species, and absent from aquatic species. A phylogram of pteridophyte families is constructed incorporating the intensity of mycorrhizal colonization as one criterion for classification.