There are 11 species of mistletoes in the genus Tristerix (Loranthaceae) endemic to the Andes in South America (1,2). Tristerix verticillatus (Ruiz & Pav.) Barlow & Wiens is distributed on the east side of the Andes from Bolivia to Argentina at high elevations (>1,500 m). On the west side of the Andes, it is only found in Chile where it occurs at low to high elevations (50 to 3,000 m). Along its range, the mistletoe parasitizes more than 25 species, mainly Anarcadiaceae and Rhamnaceae. In February of 2007, it was observed to be parasitizing Schinus fasciculatus (Griseb.) I.M. Johnst. (Anacardiaceae) at two locations in the Sierra de San Luis, Argentina. One location was 6 km south of Las Chacras on Route 31 (32°35′56″S, 65°47′6″W, elevation 1,185 m) and the other was 12 km north of El Trapiche on Route 9 (33°1′21″S, 66°4′11″W, elevation 1,260 m). At these localities, the mistletoe was in full flower and parasitized only one host species, S. fasciculatus. No mortality associated with infection by this mistletoe was observed at either location. Specimens of the mistletoe were collected from both locations and deposited at the Centro Regional Universitario Bariloche Herbarium (BCRU), Río Negro, Argentina. To our knowledge, this is the first report of a Tristerix sp. outside the Andes and extends the eastern distribution of the genus by ≈270 km and also of S. fasciculatus serving as a host for T. verticillatus since previous collections were from other species of Schinus.
References: (1) G. C. Amico et al. Am. J. Bot. 94:558, 2007. (2) J. Kuijt, Syst. Bot. Monogr. 19, 1988.
