A new species of Cuscuta (Convolvulaceae) from Michoacán, Mexico MIHAI COSTEA 1 ,IGNACIO GARCÍA RUIZ 2 , AND MARK WELSH 1 1 Department of Biology, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada; e-mail: mcostea@wlu.ca; e-mail: marcuswalby@hotmail.com 2 CIIDIR-IPN Michoacán, Justo Sierra 28 /Apdo. postal 109, Jiquilpan, Michoacán, C.P. 59510, Mexico; e-mail: igarciar2001@yahoo.com.mx Abstract. A new species, Cuscuta cotijana, is described and illustrated from the Trans-Mexican Volcanic Belt in northwestern Michoacán, Mexico. The species is most closely related to Cuscuta jalapensis, C. mitriformis, C. rugosiceps and C. lin- dsayi, from which it differs by the large spur-like projections on the outer calyx lobes and the ovoid to conical capsule with a small intrastylar aperture. Key Words: Michoacán, Mexico, Convolvulaceae, Cuscuta, Cuscuta cotijana, morphology. Cuscuta (dodder) comprises about 180 spe- cies of holoparasitic herbs with leaves reduced to minute scales; their stems are yellow to orange, filiform, trailing or dextrorsely twining, and attached to the host by numerous small haustoria (Costea & Tardif, 2006). Over 80% of the species belong to the subgenus Grammica, which is the most complex infrageneric taxon of Cuscuta, characterized by separate styles and globose stigmas (Yuncker, 1932; Stefa- nović et al., 2007). More than one third of the dodder species (69) were described between 1921 and 1961 by Truman George Yuncker (Meurer-Grimes, 1989). The boundaries of some of these species have been questioned in recent years (e.g., Beliz, 1986; Gandhi et al., 1987; Beliz, 1993). Our research within several clades of subgenus Grammica has shown that in most cases, Yuncker’ s species correspond to monophyletic entities that are recognizable by their morphological and molecular make-up (Costea et al., 2005, 2006a, b, c; Stefanović et al., 2007). Our preliminary results towards a monograph of the genus indicate that there are at least 15 to 20 new species that need to be described from North and South America to better reflect the diversity within this genus. Cuscuta is largely undercollected in México, Central America, and South America. One new species from northern Michoacán, México, is proposed in this paper, and efforts are under- way to find collaborators and resources neces- sary to reach other geographical areas that might also harbor new species. The morphology of seeds and pollen was shown to be important for the taxonomy of Cuscuta (Costea et al., 2005, 2006a, b, c). Pictures were taken with the scanning electron microscopes Hitachi S-570 and LEO 1530 FE- SEM at 15 KV. Samples were coated with 30 nm gold using an Emitech K 550 sputter coater. Terminology regarding the micromor- phology of flowers, seeds, capsules, and pollen was described in Costea et al. (2006a). Cuscuta cotijana Costea & I. García, sp. nov. Type: Mexico. Michoacán: Mun. Cotija, Los Gallineros, ca. 1900 m, 19 Apr 1991, I. García Ruiz & A. Olmos 3289 (holotype: CIMI; isotypes: IEB, IBUG, NY, UCR, WLU). (Figs. 1, 2) Cuscutae mitriformi, C. rugosicipiti, C. jalapensi et C. lindsi maxime similis, sed distincta projecturis amplis calcariformibus in lobis externis calycis et capsulis ovoideis vel conicis aperturis intrastylaribus parvis; ab C. mitriformi et C. rugosicipiti differt calyce quam tubo corollae breviore; ab C. jalapensi et C. lindsi differt floribus majoribus atque lobis corollae ac calycis auriculatis. Brittonia, 60(3), 2008, pp. 235–239 ISSUED: 30 September 2008 © 2008, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A.