Chromosome Numbers of New World Acanthaceae

Meiotic chromosome numbers were determined for 36 species representing 15 genera of Acanthaceae from Jamaica, Mexico, and Panama. Chromosome numbers of 21 species are reported for the first time including the initial reports for two genera, Oplonia (n = 21) and Streblacanthus (n = 18). Based on chromosome numbers and morphological characters, three distinctive groups of New World Justicieae: Odontoneminae are delimited. A primitive basic number of x = 7 is probable for the family. The Acanthaceae are a large, pantropical fam- ily that has only recently begun to receive con- centrated systematic analyses at both floristic and monographic levels. The proportionally large number of acanthaceous genera, includ- ing an abundance of unispecific genera, with respect to the number of species in the family is well documented (Gentry 1973, table 1; Wal- ters 1961). Previous studies of chromosome numbers in American Acanthaceae have been useful both in understanding relationships among genera and in reassessing the status of some of the unispecific genera. This paper is the third in a series of contri- butions on chromosome numbers of New World Acanthaceae. In the previous two papers (Dan- iel et al. 1984, 1990) chromosome numbers were determined for 80 species in 26 genera. Al- though we report chromosome numbers for species from Panama and Jamaica in this paper, our geographic emphasis has been, and contin- ues to be, concentrated on species occurring in Mexico. With more than 350 native and natu- ralized species in some 50 genera representing each of the four subfamilies (Acanthoideae, Mendoncioideae, Nelsonioideae, and Thunber- gioideae) traditionally recognized within the Acanthaceae, Mexico is the major center of di- versity for this family in North and Central America (Daniel, in press a).