Isotria

Abstract: cL DNA sequences, nuclear ribosomal ITS DNA sequences, morphology, and combined evidence. All these matrices produced patterns that agree on the broader Phylogenetic relationship within the clade. Duckeella is sister to all Pogoniinae, South American species of Cleistes are monophyletic, Pogonia is monophyletic and part of a larger clade of temperate taxa (Isotria, Pogonia, and Cleistes divaricata) from North America and Asia. The structure of the cladograms and the high levels of bootstrap support strongly indicate that the genus Cleistes is paraphyletic. The disjunction between tropical South American and temperate North American taxa as well as the disjunction between Pogonia ophioglossoides in eastern North America with P. minor and P. Japonica in eastern Asia are best explained by speciation following a northward longdistance dispersal and subsequent northwestward migration via Bering land bridges in the Tertiary. This phylogenetic study adds an additional herbaceous example to the growing list of plants that demonstrate this classical biogeographic pattern.

Abstract: Introduction The genus Cleistes Rich. ex Lindl. (Orchidaceae: Vanilloideae: Pogoniinae) comprises about 30 species distributed throughout Central and South America. According to Cameron & Chase (1999) and Pansarin et al. (unpubl. res.), Cleistes is paraphyletic. The North American species C. divaricata and C. bifaria are closer to the North American Pogoniinae genera Isotria and Pogonia than to the Central and South American Cleistes. The Central and South American species of Cleistes form a natural group (Cameron & Chase 1999). They are found in several habitats including disturbed areas on road margins, "campo limpo" (open grasslands), "campo sujo" (grassland with shrubs), "cerrado" (wooded savanna), "vereda" vegetation (wet grassland) in the Central Plateau, "restinga" (open seashore vegetation on sandy soil), sandy rocky soils or among rocks in "campos rupestres" (vegetation of rocky outcrops), marshy areas and "campos de altitude" (high mountain grasslands). This new species, Cleistes pusilla, was found while preparing a taxonomic revision of the genus Cleistes.

Abstract: The management of endangered or threatened plant species is difficult if protocols are not developed to propagate species for the purpose of restoration or the enhancement of existing populations. The management of endangered and threatened orchids is especially difficult because of the obligate interactions between orchids and orchid mycorrhizal fungi. Isotria medeoloides is a federally threatened forest-dwelling orchid species with a wide distribution in eastern North America. Seeds have not been successfully germinated and current management is based primarily on using subcanopy thinning to increase light in areas where monitoring demonstrates that populations are declining. We report the results of long-term monitoring efforts, canopy thinning, and orchid mycorrhizal fungus abundance studies at two locations in Virginia. The declining populations responded positively to the experimental and natural thinning of the canopy. At one site, the response was the result of understory canopy thinning. At the second site, the response was due to the natural death of a canopy tree. In light of the dramatic increase in fungal abundance following death of the canopy tree, we propose the Fungal Abundance Hypothesis as an additional approach to the management of endangered plant species. The removal of canopy trees in or adjacent to Isotria populations results in an increase in dead belowground biomass (i.e., roots of the dead canopy tree) that provides substrates for microbial growth, including orchid mycorrhizal fungi, that benefit Isotria.