Phaseolus macvaughii A. Delgado (2000: 414) [clade B; sect. Falcati Freytag].

TYPE: A Delgado et al. 129 (HOLOTYPE: MEXU-200563; ISOTYPES: ANSM-8396, ARIZ-218681, CHAPA, ENCB, IBUG-52725, MICH-1180016, MO-2575900).

The “var. no. 1” of P.micranthus (McVaugh 1987, p. 660) eventually resulted in a new species of the Falcati, with chromosome number 2n = 20 (Mercado-Ruaro & Delgado-Salinas 1998). This annual vine can be recognized by its fibrous narrow taproot, the unique dimorphism in pods and perhaps the smallest flower in the genus (Fig. 9). It grows in tropical dry forest and coastal dry scrub often close to the beach, from sea level up to 300 m. The author found it in 1978 in the dry bed of RÍo Salado in Colima, anticipating some salinity tolerance that was evidenced afterwards (Bayuelo-Jiménez et al. 2002).

Specimens: MEXICO. (northern) Baja California: P Tenorio-Lezama 10857 (ASU-179342). Sinaloa: RS Ferris 5199 (CAS-DS-149866). Jalisco: R Lépiz-Ildefonso 385 (IBUG-208597). Colima: DG Debouck 427 (US-3168522). Michoacán: E Martínez S. 4610 (IBUG-197388). Guerrero: J Acosta-Gallegos 211 (K).