FITNESS IMPACTS OF MYCOHETEROTROPHY IN CORALLORHIZA STRIATA (ORCHIDACEAE), PINUS PONDEROSA (PINACEAE), PSEUDOTSUGA MENZIESII (PINACEAE), AND TOMENTELLA FUSCOCINEREA (THELEPHORACEAE)
Anita Enriquez, D. Lee Taylor.
University of New Mexico, Albuquerque, NM.
Mycorrhizal symbioses are ubiquitous in the plant kingdom and impact the growth, community composition, and responses to stress and climate change of vegetated terrestrial ecosystems. All mutualistic symbioses are susceptible to cheating that can produce a range of evolutionary impacts including disintegration of the symbiosis. While most plants make their own food by photosynthesis, some plants have evolved mechanisms that allow them to parasitize fungi for their energetic needs. The fitness impacts of this relationship, mycoheterotrophy, are unknown. Corallorhiza striata is an obligately mycoheterotrophic orchid that possesses no chlorophyll and must interact with a fungus. This fungus, Tomentella fuscocinerea, forms mycorrhizae with surrounding trees, the ultimate source of the carbon used by the orchid. The fungus provides the orchid with carbohydrates and minerals; however, the relationship is unreciprocated and possibly detrimental to the host fungus and the linked tree. We will compare the abundance of fungi and tree growth in systems with and without C. striata. Pinus ponderosa and Pseudotsuga menziesii will be germinated in rhizotrons and inoculated with the accommodating fungus cultured from C. striata rhizomes. Half of the seedlings will receive viable C. striata seeds while the other half will receive seeds sterilized by autoclaving. Understanding the impact of cheating can shed new light on mycorrhizae, the most abundant symbiosis on land.