Mycorrhizal status of the genus Carex (Cyperaceae)

The Cyperaceae have generally been considered nonmycorrhizal, although rece nt evidence suggests that mycotrophy may be considerably more widespread am ong sedges than was previously realized. This study surveyed 23 species of Carer occurring in upland and wetland habitats in northeastern Illinois. My corrhizal infection by arbuscular fungi was found in the roots of 16 specie s of Carer and appears to occur in response to many factors, both environme ntal and phylogenetic. While some species appear to be obligately nonmycorr hizal, edaphic influences may be responsible for infection in others. In fi ve of the seven Carer species that were nonmycorrhizal, a novel root charac ter, the presence of bulbous-based root hairs, was identified. The taxonomi cally patchy distribution of the distinctive root hair trait suggests that these structures may have evolved several times within the genus. Evidence of multiple independent origins of the root hair trait lends support to the hypothesis that root hairs represent an adaptation to nonmycotrophy. Altho ugh taxonomic position does seem to be of importance in determining the myc orrhizal dependence of sedges, the pattern may be a patchwork of both mycor rhizal clades and clades that have adapted to the nonmycorrhizal state.