TEMPORAL AND SPATIAL VARIATION IN ALKALOID LEVELS IN Achnatherum robustum, A NATIVE GRASS INFECTED WITH THE ENDOPHYTE Neotyphodium STANLEY H. FAETH, 1, * DALE R. GARDNER, 2 CINNAMON J. HAYES, 1 ANDREA JANI, 1 SALLY K. WITTLINGER, 1 and THOMAS A. JONES 3 1 School of Life Sciences, Arizona State University, PO Box 874501 Tempe, AZ 85287-4501, USA 2 USDA<ARS Poisonous Plant Research Laboratory, 1150 East 1400 North, Logan, UT 84341, USA 3 USDA<ARS Forage and Range Research Laboratory, Utah State University, Logan, UT 84322, USA (Received August 5, 2005; revised October 4, 2005; accepted October 12, 2005) Published Online March 23, 2006 Abstract—The native North American perennial grass Achnatherum robus- tum (Vasey) Barkworth [= Stipa robusta (Vasey) Scribn.] or sleepygrass is toxic and narcotic to livestock. The causative agents are alkaloidal mycotoxins produced from infections by a systemic and asexual Neo- typhodium endophyte. Recent studies suggest that toxicity is limited across the range of sleepygrass in the Southwest USA. We sampled 17 populations of sleepygrass with varying distance from one focal population known for its high toxicity levels near Cloudcroft, NM, USA. For some, we sampled individual plants twice within the same growing season and over successive years (2001–2004). We also determined infection levels in each population. In general, all populations were highly infected, but infection levels were more variable near the focal population. Only infected plants within populations near the Cloudcroft area produced alkaloids. The ergot alkaloid, ergonovine, comprised the bulk of the alkaloids, with lesser amounts of lysergic and isolysergic acid amides and ergonovinine alkaloids. Levels of all alkaloids were positively correlated among individual plants within and between growing seasons. Infected plants that produced no alkaloids in 1 yr did not produce any alkaloids within the same growing season or in other years. Levels of alkaloids in sleepygrass populations declined with distance from the Cloudcroft population, although infection levels increased. Infected plants in populations in northern New Mexico and southern Colorado produced no alkaloids at all despite 100% infectivity. Our results suggest that only specific 0098-0331/06/0200-0307/0 # 2006 Springer Science + Business Media, Inc. 307 Journal of Chemical Ecology, Vol. 32, No. 2, February 2006 ( #2006) DOI: 10.1007/s10886-005-9003-x * To whom correspondence should be addressed. E-mail: s.faeth@asu.edu