Chromosome Counts from the Flora of the Juan Fernandez Islands , Chile

Thirty-four chromosome counts are reported from populations in 20 species from Masafuera in the Juan Fernandez Islands, Chile. New species counts are in Abrotanella crassipes (2n = 18), Carpobrotus aequilaterus (n = 9), Coprosma pyrifolia (n = 22), Drimys confertifolia (n = ca. 43), Euphrasia Jormosissima (n = 44), Parietaria debilis (n = 8), and UrticaJernandeziana (n = ca. 11). A new chromosomal level for Hypochoeris glabra (n = 12) also is provided. The taxonomic implications of certain of these counts are discussed. These data help extend chromosomal information for endemic taxa of the archipelago as part ofbroad evolutionary studies on the origin of the vascular plants. This study again emphasizes the absence of aneuploid or euploid chromosomal alterations during speciation within the archipelago. ONE OF THE MOST FASCINATING oceanic archipelagoes of the Pacific is the Juan Fernandez Islands. These small islands lie 600 km west of continental Chile at 33° S latitude. Having never been connected to the mainland, the Juan Fernandez archipelago has been the site of evolutionary diversification of a unique flora. Sixty-nine percent of the species ahd 18 percent of the genera of flowering plants are endemic (Skottsberg 1956), and there also exists one endemic family (Lactoridaceae). To understand patterns and processes of evolution in the endemic flora of the Juan Fernandez Islands, collaborative studies have been carried out in the botanical laboratories of Ohio State University and the University of Concepcion, Chile. One of the emphases of these studies has been the investigation of chromosome numbers to reveal the importance of chromosomal change (i.e., aneuploidy and euploidy) in the evolution of the endemic flora. Two surveys have already been published from material collected on expeditions in 1980 (Sanders et al. 1983) and in 1984 (Spooner et al. 1987). The present paper adds new data regarding the flora of the archipelago from material collected from the younger island, Masafuera, on oUr expedition in 1986. MATERIALS AND METHODS Flower buds were collected in the field, preserved in modified Carnoy's fixative (4 chloroform: 3 absolute ethanol: I glacial acetic acid), transferred to 70% ethanol back in the laboratory, and stored under refrigeration. Slide preparations were made by squashing young florets and examining developing anthers for meiotic divisions in the pollen mother cells. Acetocarmine stain was used and preparations were made semipermanent with Hoyer's medium. One count (for Abrotanella crassipes) was obtained by a squash of cells undergoing mitotic divisions in the developing embryo after fertilization. 1 This work was supported in part by NSF grant BSR8306436. Manuscript accepted October 1989. 2 Department of Biology, Chonbuk National University, Chonju, 560-756, Korea, 3 Department of Botany, Ohio State University, 1735 Neil Avenue, Columbus, Ohio 43210. RESULTS Thirty-four new chromosome counts for taxa growing on Masafuera are listed in Table 1. First counts are reported for seven species: Abrotanella crassipes (Asteraceae), Carpobrotus aequilaterus (Aizoaceae), Coprosma pyri-