Additional Chromosome Numbers of American Acanthaceae

Original meiotic chromosome counts are presented for 39 species in 15 genera of Acanthaceae from Belize, Costa Rica, Ecuador, Mexico, Panama, the United States, and Venezuela. These reports include the first counts for 20 species representing 10 genera of the family, including the first chromosome number documented for the genus Poikilacanthus. Counts for 15 species confirm numbers previously reported for them from different sources. New chromosome numbers are reported in two genera, Carlowrightia (« = 17 in C. pectinata) and Justicia (n = 24 in /. galapagana). New chromosome numbers are also reported in two species of Justicia, J. comata {n = 28) and /. oerstedii (n = 11). Systematic implications of these chromosome numbers are addressed where appropriate. The Acanthaceae are a pantropical family with more than 4,000 species in some 230 genera. Major concentrations of species occur in southeastern mainland Asia, insular Malesia, India, Madagascar, tropical Africa, Brazil, Andean South America, and Mexico-Central America. Studies of phylogenetic relationships within the family are in their infancy. As a result, putative relationships are usually based on Lindau's (1895) outdated but complete classification of the family or Bremekamp's (1965) improved but incomplete infrafamilial classification. Like many other large and predominately tropical families of flowering plants, the Acanthaceae remain poorly known cytologically. Based on the summaries of chromosome counts cited below, chromosome numbers have been determined for approximately 468 species (or less than 12% of total species) in the family. In addition, one or more counts are known for only 67 of the 228 genera of Acanthaceae (i.e., 29%) recognized in Brummitt (1992). Counts have been determined for only a single species in 25 of these 67 genera. During the past 20 years my research has focused on Acanthaceae in North America and Central America, a region in which about 500 species are known to occur These species represent natural occurrences of taxa for three of the four traditionally recognized subfamilies of Acanthaceae (Lindau 1895): Acanthoideae, Mendoncioideae, and Nelsonioideae. Several species of the fourth subfamily, Thunbergioideae, are naturalized in this region. This study is a further contribution toward providing basic cytological information on American Acanthaceae. As in several previous studies on chromosomes of Acanthaceae (Daniel et al. 1984, 1990; Daniel and Chuang 1993), most of the plants studied here are from Mexico and Central America. Previous studies of chromosome numbers of plants from this region have helped to reassess the taxonomic status of some unispecific genera, suggest relationships among genera, and establish probable basic numbers for genera. MATERIALS AND METHODS Between 1982 and 1998, buds and herbarium vouchers of 60 species of Acanthaceae were collected from their native habitats in various countries of the Western Hemisphere. Some plants were grown at the San Francisco Conservatory of Flowers from seeds collected in the field (indicated by "cv" or "gh" following the field collection number). Buds were collected from these plants in the greenhouse and vouchers were made from the cultivated plants. My collection of Justicia galapagana (Daniel s.n.cv) was taken from a greenhouse-cultivated plant grown from seed collected on Santa Cruz Island in the Galapagos Islands (i.e., no collection was made in the field). Floral buds for chromosome studies were fixed in absolute ethanokglacial acetic acid (3: 1) for 24 hours and subsequently washed and stored in ethanol (70%) until analyzed. Anthers were macerated in ferric acetocarmine (1%) and counts were made from microsporocytes in various stages of meiosis. Chromosomes were studied under oil immersion on a phase contract microscope at a magnification of lOOOx. Counts from at least two cells were made for most collections and all counts were verified by at least two persons. Preparations from which counts were obtained were recorded with camera lucida drawings. Voucher spec-