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The geographic and host distributions of Arceuthobium hondurense and A. nigrum (Viscaceae) in southern Mexico and Central America have remained unclear due to difficulties in their identification. This study was conducted to clarify the morphology, phenology, distribution, and host affinities of these dwarf mistletoes. Morphological measurements were made for these species across their geographic distributions and nr ITS sequences were generated and compared from selected populations in Mexico. Although subtle, interspecific differences in plant morphology were found, A. hondurense and A. nigrum can be differentiated by the dimensions of their staminate spikes, staminate flowers, and fruits. Our data also indicated that A. hondurense and A. nigrum were not sympatric. Arceuthobium hondurense is distributed from northern Nicaragua to northern Oaxaca, Mexico and A. nigrum is distributed from Veracruz to northern Durango. Although A. hondurense and A. nigrum flowered in the fall, A. hondurense consistently peaked in September and A. nigrum peaked in October, extending into January in central Mexico. A spring flowering period reported previously for A. nigrum was not observed. Additional information on the host distribution and molecular differences of these dwarf mistletoes is also presented. [ABSTRACT FROM AUTHOR]