DISTRIBUTION AND DISPERSAL OF XYLARIA ENDOPHYTES IN 2 TREE SPECIES INPUERTO-RICO

Xylaria species are common endophytes in tropical plants. It is not kn own, however, whether transmission of Xylaria occurs horizontally or v ertically, whether individual Xylaria strains have wide host ranges or are host-specific, or how they are dispersed. We compared frequency o f Xylaria endophytes in leaves and seeds of two tree species in Puerto Rico, Casuarina equisetifolia (Australian pine) and Manilkara bidenta ta (ausubo). These trees were chosen because they differ markedly in m orphology, habitat, distribution, and origin. In C. equisetifolia Xyla ria was significantly more frequent in leaves than in seeds. Xylaria w as isolated from seeds of trees in inland parks, but never from seeds of trees growing on beaches. This suggests that vertical transmission of Xylaria may be possible but is not necessary for infection. In M. b identata, Xylaria was isolated from 97% of leaves but was never isolat ed from seeds, suggesting that transmission is entirely horizontal. Se edlings raised in a greenhouse far from other M. bidentata trees had a level of Xylaria infection as high as seedlings in the forest, sugges ting that inocula can come from other sources and endophytic strains a re not host-specific.