CHROMOSOME NUMBERS AND PHYLOGENY IN MELAMPODIUM (COMPOSITAE)

The haplord chromosome numbers of n = 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species of Melampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series of x2 = 9, 10, 11, and 12. Of these four groups of species, the x = 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base in Melampodium. A comparison of morphological and cytological data from the closely related genera, Acanthospermum and Lecocarpus, indicates that the latter are probably on a common base of x = 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.     

CHROMOSOME NUMBERS IN CENCHRUS (GRAMINEAE)

Gametic chromosome numbers are reported for 22 populations representing 6 taxa in the genus Cenchrus. Numbers of n = 17 were obtained for C. incertus M. A. Curtis, C. longispinus (Hack.) Fern., and for the previously unreported C. mitis Anderss. Populations of C. echinatus L. have the number n = 34, and C. myosuroides H.B.K. n = 35. Irregular meiosis was observed in 2 chromosomal races of C. ciliaris L. having numbers of n = 18 and n = ca. 16, respectively.     

CHROMOSOME NUMBERS IN CHEILANTHES AND POLYPODIUM

Six chromosome observations are reported, two being confirmations and four being new counts. Polypodium plesiosorum (from Mexico) shows 37 pairs at meiotic metaphase and thus conforms to past counts of diploid species in this genus. Cheilanthes wrightii (Arizona) has 2n = 58 and is a diploid member of the x = 29 series of that genus. Cheilanthes tomentosa (Alabama) shows 90 units at metaphase of meiosis and approximately the same number during mitosis in the crozier cells. It has 32 spores and our plant is an apogamous triploid. Both Cheilanthes siliquosa (Washington) and C. californica (California) show 30 pairs at meiotic metaphase. Counts on plants identified as C. carlotta-halliae (California) show 30 bivalents and 30 univalents at diakinesis, suggesting that they actually represent allopolyploid backcrosses of C. carlotta-halliae and one of its parents.     

CHROMOSOME NUMBERS AND THEIR SYSTEMATIC IMPLICATIONS IN HAWAIIAN LOBELIOIDEAE (CAMPANULACEAE)

Chromosome numbers are reported for 20 collections of Hawaiian Lobelioideae (Campanulaceae), representing six genera, 13 species, and two interspecific hybrids. All are n = 14. Chromosome numbers are reported for the first time for eight species of Clermontia, Cyanea, Delissea, Lobelia, and Trematolobelia; the report for Delissea is the first for that genus. Additional determinations confirmed previously reported numbers in five other species of Brighamia, Clermontia, and Cyanea. Chromosome numbers are now known for all seven genera and 20 of the 110 species. All accepted counts are n = 14. It is suggested that all Hawaiian Lobelioideae share this number and are paleotetraploid. There is no evidence that the prolific speciation evident among these plants was accompanied by euploid or aneuploid change in chromosome number. The Hawaiian Lobelioideae, particularly the monophyletic lineage of 91 baccate species, offer further support for the generalization that change in chromosome number is an uncommon mode of speciation in insular floras.     

CHROMOSOME NUMBERS IN PLATYSCHKUHRIA RYDBERG (COMPOSITAE) AND THEIR SYSTEMATIC SIGNIFICANCE

Diploid (2n = 12_II), tetraploid, pentaploid, and hexaploid level chromosome numbers are reported for Platyschkuhria Rydb. (Compositae). First reports of accessory chromosomes in the genus are also presented. Known polyploidy in Platyschkuhria is thus far restricted to P. integrifolia (Gray) Rydb. var. desertorum (M. E. Jones) Ellison from south-central Utah. Cytogenetic analysis, using methods and models of Jackson and Hauber (1982), suggests alloploid origins for the tetraploid levels. Diploid and polyploid populations correlate strongly with distinctively different edaphic situations, yet no consistent morphological features were identified that could justify taxonomic recognition of the polyploids.     

NEW BASIC CHROMOSOME NUMBERS FOR GENERA OF NEOTROPICAL FERNS

Chromosome numbers for eight genera of Costa Rican ferns are reported here for the first time. These are: Neurocallis, n = 58; Marginariopsis, n = 35; Dicranoglossum, n = 36; Glyphotaenium, n = 37; Cochlidium, n = 33; Ormoloma, n = 42; Peltapteris, n = 40; and Loxsomopsis, n = 46. Chromosome observations involving several other genera are included: Solanopteris, n = 37; Xiphopteris, n = 32; Hemidictyum, n = 31: Pleuroderris, 2n = 80; Dictyoxiphium, 2n = 80; and Polystichum, n = 41. These numbers are compared to those of genera of presumed taxonomic affinity.     

竹柏染色体数目和形态

本文对竹柏(Podocarpus nagi(Thb.)Zoll.et Moritz.ex Zoll.)的染色体组型进行了初步观察。观察结果:染色体数目2N=29;染色体长度变化在3.32—6.21微米之间;其相对长度的变动范围是5.29—9.90％;臂比表明有6对染色体具有中部着丝点,7对染色体具有近中部着丝点,其中有2个随体。     

CHROMOSOME NUMBERS IN CUPHEA (LYTHRACEAE): NEW COUNTS AND A SUMMARY

The American genus Cuphea with ca. 260 species is extremely diverse with respect to chromosome number. Counts are now available for 78 species and/or varieties, or 29% of the genus. Included in this study are first reports for 15 taxa from Brazil, Cuba, Dominican Republic, Mexico, and Venezuela. Twenty-two different numbers are known for the genus, ranging from n = 6 to n = 54. The most common number in the primary center of species diversity in Brazil is n = 8, which is regarded as the base number of the genus. Two numbers are most common in the secondary center in Mexico, n = 10 and n = 12. Species with n = 14 or higher are considered to be of polyploid origin. Polyploids comprise 46% of the total species counted and appear in 9 of the 11 sections for which chromosome numbers have been reported. Aneuploid species comprise ca. 25% of the genus and are known from 7 of the 11 sections. The two subgenera are not characterized by different chromosome numbers or sequences of numbers. None of the 14 sections are circumscribed by a single chromosome number. Morphological and ecological variability in widespread, weedy species is correlated with differing chromosome numbers in some species whereas in others the chromosome number is stable. Summary of chromosome numbers by taxonomic section is presented. Section Euandra, centered in eastern Brazil, and the largest section of the genus, appears to be chromosomally most diverse. In section Trispermum, characterized by difficult, variable species with intermediate forms, two of the four species studied have polyploid races. Section Heterodon, endemic to Mexico and Central America and comprising most of the annual species of the genus, is best known chromosomally. Chromosome numbers have been counted for 25 of 28 species, and 12 different numbers are reported. The most advanced sections, Melvilla and Diploptychia, with numerous species occurring at higher altitudes, are characterized by high polyploids. Apomictic species occur in sect. Diploptycia. The cytoevolution of Cuphea is complex with frequent polyploid and aneuploid events apparently playing a significant role in speciation in both centers of diversity.     

CHROMOSOME NUMBERS AND THEIR SYSTEMATIC IMPLICATIONS IN LIPOCHAETA (COMPOSITAE:HELIANTHEAE)

Chromosome counts are reported for 71 collections in 14 taxa of Lipochaeta DC. (Compositae) of the Hawaiian Islands. Counts for 13 of the taxa are first reports. Lipochaeta contains diploids, n = 15, and tetraploids, n = 26. Ploidy level is taxonomically significant for recognizing sections, and on the basis of these data, together with morphological and chemical evidence, major realignments of species into the secions of Lipochaeta have been made.     

CHROMOSOME NUMBERS IN BROMELIACEAE

Eighty-three chromosome counts are reported for 72 taxa of the Bromeliaceae. Fifty-eight of these counts are the first known chromosome number reports for their respective taxa. A model of chromosomal evolution in the Bromeliaceae (n = 25) is presented. The model is parsimonious and consistent with existing data on meiotic chromosome numbers within the family and in the closely related Velloziaceae (n = 9). Two hypothesized paleodiploids (n = 8 and n = 9) hybridized to form a tetraploid that in turn hybridized with the n = 8 lineage. The resultant n = 25 is the extant base number for the family. Two alternative hypotheses could explain the unique extant base number (n = 17) for Cryptanthus: 1) Cryptanthus represents the paleotetraploid level, i.e., prior to the second round of hybridization, or 2) the lower number represents the result of a more recent series of aneuploid reductions from n = 25. Given the existence of intergeneric hybrids involving Cryptanthus, aneuploid reduction is the more likely interpretation.     

山茶属植物的染色体数目和核型

本文对已报道的(包括作者的研究)山茶属植物的染色体数目和核型作一简单的讨论,结合地理分布情况,提出由二倍体向多倍体进化可能是山茶属植物进化的一个重要途径。山茶属植物的核型多为Stebbins核型分类的“2A”型,表明山茶属植物是一个较原始的种系。本文中12种的染色体数目和2种的核型为首次报道。     

CHROMOSOME NUMBERS IN THE GENUS ANTHURIUM (ARACEAE) II

Chromosome numbers were determined for 86 Anthurium species. Fifty-one of these were newly determined with counts ranging from 2n = 24 to 66 and 30 being the most common. All known Anthurium chromosome numbers were summarized, and 43 taxonomic changes were made in the previous reports to reflect current taxonomy. In terms of somatic chromosome numbers, the numbers form four polyploid series of 20–40–60, 24–30–48–84, 28–56 and 30–60–90–ca. 124. Paleoaneuploidy, polyploidy and B-chromosomes are basic features of the genus, but subsequent recent aneuploidy is not. The exact nature of chromosome evolution in Anthurium remains to be elucidated.     

SYSTEMATIC SIGNIFICANCE OF CHROMOSOME NUMBERS IN ACMELLA (ASTERACEAE)

Chromosome counts are reported for 372 individuals from 202 populations in 26 taxa of Acmella (Asteraceae: Heliantheae). Chromosome numbers for 15 taxa are first reports. A review of previous counts and the new reports supports a basic chromosome number of 13 for the genus. The results show that polyploidy, sometimes accompanied by hybridization and asexual reproduction, is widespread in Acmella and has contributed to the taxonomic difficulties in the genus. These factors have produced a variable polyploid pillar complex in sect. Acmella. In one taxon in this complex, A. oppositifolia var. oppositifolia, intrataxon and even intrapopulational chromosomal variation has been detected. Morphological studies in conjunction with observations of meiotic pairing suggest that most polyploids are alloploid in origin. The occurrence of polyploidy in 16 of the 27 taxa known chromosomally emphasizes the important role this process has had in speciation within Acmella. Although intrataxon chromosomal variation has limited the taxonomic utility of chromosome numbers, a few examples are presented in which these data have been valuable for separating some pairs of closely related taxa (A. decumbens var. affinis from var. decumbens and A. poliolepidica from A. oppositifolia).     

AMYLASE POLYMORPHISM IN CITRUS AND SOME RELATED GENERA

Amylase polymorphism was studied by electrophoresing crude protein extracts from mature leaves of Citrus and some related genera in polyacrylamide gel slabs. A total of 25 isoenzymes distributed within 2 distinct zones were resolved. Cultivars of C. medica were the least polymorphic with 5 isoenzymes, those of C. paradisi were the most polymorphic with 14 isoenzymes; the other taxa were between these two extremes. Cultivars within species, in general, had no qualitative differences in their isoenzymes profiles with the exception of C. aurantifolia, C. limon, and C. aurantium. Certain isoenzymes showed quantitative differences among taxa. Data provided evidence substantiating the presumed hybrid origin of some taxa. The potential of isoenzyme profiles in taxonomic and genetic studies was discussed.