CHROMOSOME NUMBERS OF HAWAIIAN FLOWERING PLANTS AND THE SIGNIFICANCE OF CYTOLOGY IN SELECTED TAXA

Chromosome numbers are reported for 128 species of flowering plants indigenous or endemic to Hawaii, including first reports for 13 genera and 82 species. The special significance of reports for Ilex, Tribulus. KeNsseria, Pisonia, Boerha0ia Jacquemontia, Claoxylon, Lipochaeta, Railliardia, and Dubautia are discussed. The cytological and morphological variation in Railliardia and Dubautia is considered and their treatment as congeners is advocated. The cytogeographic pattern in Dubautia and Railliardia and other factors suggest that the ancestral chromosome number of the Hawaiian tarweeds is n = 14. Their derivation from a western North American progenitor similar to Adenothamnus is considered plausible if not indeed likely. CHROMOSOME NUMBERS have been reported for about 165 (11.4%) of Hawaii's 1,442 species of native flowering plants as enumerated by St. John (1973). The only extensive, general cytological survey of Hawaiian plants is that of Skottsberg (1955). Additional chromosome reports of Hawaiian taxa have resulted from concerted efforts in the genera Bidens (Gillett and Lim, 1970), Pipterus (Nicharat and Gillett, 1970), and Wikstroemia (Gupta and Gillett, 1969). Supplementary stray reports have been made mostly by mainland botanists interested in the Hawaiian representatives of their chosen taxonomic specialties. The most significant recent contribution is Gardner's study of Lipochaeta (1977). The purpose of this paper is to present new data thus far accumulated in an ongoing cytological survey of the flowering plants of Hawaii. Intentional emphasis has been given to the Hawaiian tarweed genera Dubautia and Railliardia. The possible significance of chromosome numbers in these and certain other taxa is discussed below. Chromosome numbers of 160 collections representing 128 species, 80 genera, and 50 families are presented herein. These include first reports for 82 species and 13 genera. This brings the total number of Hawaiian species cytologically determined to about 247 (17.1%). All chromosome numbers reported here are gametic numbers determined by observation of meiotic configurations of microsporocytes. ' Received for publication 6 June 1977; revision accepted 17 August 1977. This study was supported by a Faculty Research Grant from the University of Hawaii. I am very grateful to the many individuals who contributed directly or indirectly to the accumulation of cytological materials for this study, especially Lani Stemmermann. Floral buds for study were preserved and stored in modified Carnoy's fixative (6 chloroform:3 absolute ethanol: I glacial acetic acid; v:v). Anthers were squashed in acetocarmine and slides were made permanent by addition of Hoyer's solution (cf. Beeks, 1955). Voucher specimens of taxa reported on here are deposited at HAW. DISCUSSION-The counts of some of the species reported here (Table 1) are unique or otherwise distinctive enough to warrant their discussion in relation to other reports for the same or related taxa. For example, the counts for Ilex anomala (n = 40), Tribulus cistoides (n = 18), and Keysseria maviensis (n = 27) represent the highest polyploid levels known in these species. Likewise, the first count for Pisonia (n = 68, possibly an octoploid on base 17) reported here is the highest number recorded in the Nyctaginaceae. The second highest number in this family, 2n = 116 (Thombre, 1959), reported for Boerhavia diffusa probably represents a nonaploid since 2n = 26 has also been recorded for the species (Srivistava & Misra, 1966). The Hawaiian representatives of Ilex and Boerha via diffusa (n = 26) are the only tetraploids known in these taxa. Likewise, Hawaiian material of Tribulus cistoides represents the only hexaploids known in that species. The only previous number recorded for T. cistoides is n = 6 (diploid) based on material from Mexico, Colombia and Jamaica (Porter, 1964, 1967). The only previous report for the genus Keysseria is based on K. radicans (n = 18) from New Guinea (Borgmann, 1964). The related genus Lagenophora has been reported to have n = 9 (Arano, 1965). Thus, it appears that Keysseria maviensis is a hexaploid and in this regard it is interesting to note that the Hawaiian material