KARYOTYPE ANALYSIS IN SOME GENERA OF COMPOSITAE. VIII. FURTHER STUDIES ON THE CHROMOSOMES OF ASTER

Huziwara , Y. (Kobe U., Mikage, Kobe, Japan.) Karyotype analysis in some genera of Compositae. VIII. Further studies on the chromosomes of Aster. Amer. Jour. Bot. 49 (2) : 116–119. Illus. 1962.—The karyotypes of 3 Asiatic and 3 American taxa of Aster are reported here for the first time. These are: A. ageratoides subsp. sugimotoi (Kitamura) Kitamura 2n = 36, A. ageratoides subsp. (Taxon AIII) 2n = 72, A. himalaicus C. B. Clarke 2n = 18, A. ericoides L. 2n = 32, A. meritus A. Nels. 2n = 27, A. umbellatus Mill. 2n = 18. Two American taxa, namely, A. meritus and A. umbellatus, are considered to be ancestral taxa which have retained primitive karyotypes similar to those of Asiatic species of Aster.     

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.     

HYBRIDIZATION BETWEEN ASTER AND MACHAERANTHERA AND ITS TAXONOMIC SIGNIFICANCE

A controlled crossing program resulted in the production of four interspecific and three intergeneric hybrids among species of Aster sect. Oxytripolium and Machaeranthera. Meiotic analysis revealed stronger degrees of genome homology in some of the intergeneric hybrids than in some of the interspecific hybrids. The significance of these results to the taxonomy of Aster and Machaeranthera was considered and the result was the transfer of Aster sonorae to Machaeranthera.     

Aster saxicola sp. nov. (Asteraceae,Astereae), a new species from Guizhou,China: evidence from morphological,molecular and cytological studies

Aster saxicola W. P. Li & Z. Li, a new species of Asteraceae from southeastern Guizhou province, China, is described and illustrated based on morphological, molecular and cytological data. Morphological comparisons showed that A. saxicola is similar to A. oliganthus, but can be distinguished from the latter by its purple abaxial surface of the lower and middle cauline leaves, cordate‐ovate basal leaves with strigose hairs, outer three‐seriate phyllaries with purple or purplish apex, 9–14 ray florets and 10–18 disk florets. Phylogenetic analyses based on nrDNA ITS, ETS and plastid trnL–F DNA sequence data support that A. saxicola is a distinct species and belongs to Aster subgen. Aster sect. Ageratoides. Cytological observation shows that the new species is diploid with a karyotype formula 2n = 2x = 18 = 16m + 2sm. The new species should be considered endangered (EN) based on the IUCN red list criteria because of its restricted geographic range.     

CHROMOSOME NUMBERS IN PERITYLE AND RELATED GENERA (PERITYLANAE-COMPOSITAE)

Chromosome numbers are presented for 28 species of the genus Perityle, one putative inter-sectional hybrid, two species of Amauria, one species of Eutetras, and one species of Pericome. For Perityle, initial counts are recorded for 12 species of sect. Laphamia (n = 16, 17, 18, 36, ca. 102) and 11 species of sect. Perityle (n = 11, 12, 13, 16, 17, 18, 19, 34, 51). Chromosome numbers for the two species of Amauria (n = 18) are first reports for the genus. Including the current information, chromosome numbers have been recorded for 37 of the approximately 50 species recognized for Perityle. At least 24 taxa have numbers of n = 17, suggesting a base chromosome number of x = 17 for Perityle.     

CHROMOSOME NUMBERS IN THE COMPOSITAE. IV. NORTH AMERICAN SPECIES,WITH PHYLETIC INTERPRETATIONS

Turner , B. L., W. L. Ellison , and R. M. King . (U. Texas, Austin.) Chromosome numbers in the Compositae. IV. North American species, with phyletic interpretations. Amer. Jour. Bot. 48(3): 216–223. Illus. 1961.—Chromosome counts from 116 different plant populations representing 75 taxa (72 species in 39 genera) are reported. These include the first species counts for the following genera: Actinospermum (x = 19), Baltimora (x =15), Calea (x = ca. 17, 18), Calyptocarpus (x = 12), Hecubaea (x = 17), Lagascea (x = 17), Schistocarpha (x = 8), Melanthera (x = 15), Pectis (x = 12), Perymenium (x = 15), Sanvitalia (x = 8), and Trigonospermum (x = 15). Chromosome counts for Chrysopsis trichophylla (n = 5), Cirsium horridulum (n = 16), Hidalgoa ternata (n = 16,) Tridax balbisioides (n = 10), Tridax trilobata (n = 10), and Verbesina crocata (n =18) differ from the reported basic numbers as determined from other species in these genera. Taxa closely related to Tridax procumbens were found to have the diploid number n = 9, thus establishing the polyploid nature (n = 18) of this widespread polymorphic species. When appropriate, the chromosomal information has been related to systematic problems.     

CHROMOSOME NUMBERS IN THE LEGUMINOSAE. III. SPECIES OF THE SOUTHWESTERN UNITED STATES AND MEXICO

Turner, B. L., and Olin S. Fearing. (U. Texas, Austin.) Chromosome numbers in the Leguminosae. III. Species of the Southwestern United States and Mexico. Amer. Jour. Bot. 47(7) : 603–608. Illus. 1960.—Chromosome counts for 43 species of the Leguminosae from the southwestern United States and Mexico have been reported. These include first reports for 42 taxa of which 16 are for the subfamily Mimosoideae. Olneya tesota (2n = 18) is the only new generic count listed. Chromosome reports of particular significance include a single polyploid count for a North American species of Acacia, as well as diploid and tetraploid counts for closely related taxa in this genus. Four species of the genus Schrankia were found to be diploid with In = 26, indicating a base of x = 13 instead of the x = 8 reported by some previous workers. Leucaena pulverulenta was found to have a diploid count of 2n = 56 indicating a base of x = 14.     

CYTOGEOGRAPHY AND PHYLOGENY OF THE NORTH AMERICAN SPECIES OF VERBENA

Lewis , Walter H., and Royce L. Oliver . (Stephen F. Austin State Coll., Nacogdoches, Texas.) Cytogeography and phylogeny of the North American species of Verbena. Amer. Jour. Bot. 48(7): 638–643. Illus. 1961.—Chromosome numbers of 26 Verbena species in North America, separable into 2 series, are reported. The x = 5 series has no diploid representative, few tetraploids, and numerous widespread hexaploid species, while the x = 7 series has many pandemic diploid species and few tetraploid and hexaploid taxa. When compared with the data available for the South American verbenas, these frequencies and distributions were found to be almost opposite. The origin of the 2 groups from an x = 6 prototype followed by ascending and descending aneuploidy is suggested. Migration via tropical land bridges is proposed to explain the occurrence of both groups in the 2 continents. The following taxa are proposed: subgenus Verbenaca (Schauer) Lewis, and subgenus Glandularia (Gmelin) Lewis.     

EVOLUTIONARY STUDIES OF ATRIPLEX: CHROMOSOME RACES OF A. CONFERTIFOLIA (SHADSCALE)

Atriplex confertifolia (Torr. and Frem.) S. Wats., a species endemic to western United States, occurs as 2n, 4n, 6n, 8n and 10n chromosome races. In the Great Basin, diploids occur altitudinally above the upper levels of Pleistocene lakes; the polyploids are in valley bottoms and sides. Diploids are larger in all respects than tetraploids, hexaploids, and octoploids. Decaploids are the most robust of all. Diploids can be distinguished in early seedling stages by having broader leaves and shorter internodes than polyploids. Polyploid plants are currently produced sporadically in natural populations and appear to be easily generated by unreduced gametes. Most polyploid populations in the Great Basin apparently arose recently and erupted into extensive stands because of the sudden availability of large, relatively uniform domains provided by the disappearance of Pleistocene lakes.     

The use and limits of AFLP data in the taxonomy of polyploid wild potato species in Solanum series Conicibaccata

Solanum sect. Petota (tuber-bearing wild and cultivated potatoes) are a group of approximately 190 wild species distributed throughout the Americas from the southwestern United States south to Argentina, Chile, and Uruguay. Solanum series Conicibaccata are a group of approximately 40 species within sect. Petota, distributed from central Mexico to central Bolivia, composed of diploids (2n = 2x = 24), tetraploids (2n = 4x = 48) and hexaploids (2n = 6x = 64); the polyploids are thought to be polysomic polyploids. This study initially was designed to address species boundaries of the four Mexican and Central American species of series Conicibaccata with AFLP data with the addition of first germplasm collections of one of these four species, Solanum woodsonii, as a follow-up to prior morphological, chloroplast DNA, and RAPD studies; and additional species of series Conicibaccata from South America. AFLP data from 12 primer combinations (1722 polymorphic bands) are unable to distinguish polyploid species long thought to be distinct. The data suggest a complex reticulate history of the tetraploids or the need for a broad downward reevaluation of the number of species in series Conicibaccata, a trend seen in other series of sect. Petota. Separately, through flow cytometry, we report the first ploidy level of S. woodsonii, as tetraploid (2n = 48). The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

TAXONOMIC SIGNIFICANCE OF CHROMOSOME OBSERVATIONS IN CARIBBEAN SPECIES OF LANTANA (VERBENACEAE)

Chromosome numbers and, in most cases, meiotic configurations are provided for 12 taxa and 5 morphological intermediates of Lantana collected in the Bahamas, Dominican Republic, Florida, the Lesser Antilles, Puerto Rico, and Texas. Reported for the first time are Lantana bahamensis, n = 11; L. microcephala, n = 12; L. leonardiorum, n = 11; L. odorata, n = 12; L. reticulata, n = 24; L. subcordata, n = 11; L. urticifolia, n = 11, 22. Numbers differing from previous reports were obtained for L. involucrata, n = 12, 24, and L. trifolia, n = 27. Triploids indicate the natural occurrence of hybridization between diploid and tetraploid taxa. Bivalents are formed regularly, except in the triploids and in morphologically intermediate tetraploids. These reports confirm that Lantana is based on at least two numbers, x = 11 and 12, and that the genus comprises polyploid complexes in each of these basic lines. The polyploids are weedier and more widely distributed than are the diploids. Chromosome numbers and configurations aid in the delimitation of diploid foundation species and in the recognition of naturalized hybrids.     

BIOSYSTEMATIC STUDIES IN THE BOUTELOUA CURTIPENDULA COMPLEX. III. POLLEN SIZE AS RELATED TO CHROMOSOME NUMBERS

Pollen size statistics are presented for 10 closely related species of Bouteloua and relationships between pollen size and chromosome numbers are presented for 13 populations of 5 species and 3 varieties. With 1 exception, all populations of all taxa conformed to a general pattern of pollen size dependent upon chromosome number. Chromosome numbers varied from 2n = 20 to 2n = ca. 103, with several independent aneuploid series. Statistical analyses were made of pollen size as related to chromosome number in the 3 varieties of B. curtipendula. These data showed that tetraploids (2n = 40) of var. tenuis had significantly greater pollen size and coefficient of variation than diploids (2n = 20) of the same variety. Similarly, aneuploids of var. curtipendula with 2n = 45 to 2n = 64 chromosomes had significantly larger and more variable pollen than tetraploids (2n = 40) of the same variety. Highly significant positive regression coefficients were obtained from analyses of chromosome numbers and mean pollen size, and chromosome numbers and coefficient of variation, for var. curtipendula. Regression coefficients for var. caespitosa populations with chromosome numbers over the hexaploid (2n = 60) level were not significant.     

CHROMOSOME NUMBERS IN COMPOSITAE V. ASTEREAE II.

Reports of 100 new chromosome counts are made for the tribe Astereae of Compositae, mostly based on determinations of meiotic material, including first counts for 9 genera and 53 species. Counts are now available for 58 of the approximately 100–120 genera and 431 of the approximately 2000 species in the tribe. Comparisons are made between chromosome number and habit and also between chromosome number and geographical distribution. Species and genera with a basic number of x = 9 are the most abundant. Within different phyletic lines x = 9 is also the most abundant number. On the other hand, many species with x = 4 and 5, belonging to a number of small, largely annual genera, are concentrated in southwestern North America. The low chromosome number in these plants is probably correlated with the dry habitat they occupy, and is most likely a specialized condition.     

CHROMOSOME NUMBERS IN THE COMPOSITAE: COLOMBIAN SPECIES

Chromosome numbers are presented for 76 species belonging to 35 genera of Compositae from Colombia. Thirty-nine species and three genera, Espeletia (x = 19), Steiractinia (x = 14), and Vasquezia (x = 19), are reported for the first time. New base numbers or chromosome series are recorded in Baccharis (B. nitida, n = 25), Calea (C. caracasana, n = 24), and Liabum (L. mega-cephalum, n = 10).     

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.     

A classification of the New World species of Aster (Asteraceae)

In order effectively to list and comment on the results of cytological investigations inAster in a companion paper, a scheme of infrageneric classification is presented which utilizes the basic chromosome number as a pivotal diagnostic character. Reasons are stated as to why, with the exception ofUnamia Greene which is transferred toSolidago, and the commonly recognized generaLeucelene Greene,Machaeranthera Nees andXylorhiza Nutt., none of the segregate genera previously proposed or recorded in the literature is upheld. Instead, these taxa are being given subgeneric or sectional rank. Two additional subgenera are established to accommodate the species groups traditionally placed in “Aster proper,” which are characterized by having basic chromosome numbers ofx = 5 andx = 8, respectively. Altogether ten subgenera of the genusAster, five of them subdivided further into a total of 24 sections, are recognized as having representative species in the New World. All basionyms and type species are listed, and a number of new combinations and status changes are validated in accordance with the International Rules of Botanical Nomenclature. Where known (from literature and personal research), chromosome numbers are recorded for the species.     

CYTOGEOGRAPHIC STUDIES ON NORTH AMERICAN ASTERS. I. RANGE SURVEYS OF VIRGULUS ADNATUS,V. CONCOLOR,V. GEORGIANUS,V. GRANDIFLORUS,V. NOVAE-ANGLIAE,V. OBLONGIFOLIUS,V. PATENS,AND V. WALTERI

Chromosome number determinations from 118 populations of eight species of the aster genus Virgulus are reported for the first time. Based on these counts and literature reports the geographic distributions of diploids and tetraploids in V. concolor, V. novae-angliae, V. oblongifolius, and V. patens have been determined. In the first three species, diploids were widely distributed, while tetraploids were more restricted. In V. patens, diploids were restricted to the southwestern portion of the species’ range, while tetraploids were found throughout the range. Both V. adnatus and V. walteri were found only at the tetraploid level throughout their ranges. Two other species with restricted distributions were consistently found to be high level polyploids: V. georgianus with 2n = 50, V. grandiflorus with 2n = 60. The following new combinations are listed: Virgulus georgianus (Alexander ex Small) Semple; Virgulus subsect. Brachyphylli (Torr. & Gray) Semple; and Virgulus sect. Polyliguli (Semple & Brouillet) Semple.     

THE HYBRID ORIGIN OF ASTER ASCENDENS (ASTERACEAE)

Aster ascendens Lindl. is a rhizomatous perennial of the Great Basin region of the western United States, with a chromosome base number of x = 13. Populations in the southern and western parts of the range are mainly diploid (n = 13) and those in the north and east are mainly tetraploid (n = 26). This species is postulated to be an amphiploid which has resulted from hybridization between the western Cordilleran A. occidentalis (T. & G.) Hook, and the Great Plains species A. falcatus Lindl. Aster ascendens is intermediate between these two species in most morphological traits, but resembles A. occidentalis in ray color and general growth habit, and A. falcatus in the shape of the outer phyllaries. The karyotype of A. ascendens also exhibits a combination of the features found in A. occidentalis and A. falcatus karyotypes. Of the specimens collected for this study, 13% were putative backcrosses of A. ascendens to one of its parent taxa or to a closely related species; this suggests that there is potentially continuing genetic interchange between the species groups that gave rise to A. ascendens.     

INTERSPECIFIC HYBRIDIZATION IN HAPLOPAPPUS AND ITS BEARING ON CHROMOSOME EVOLUTION IN THE BLEPHARODON SECTION

Jackson , R. C. (U. Kansas, Lawrence.) Interspecific hybridization in Haplopappus and its bearing on chromosome evolution in the Blepharodon section. Amer. Jour. Bot. 49 (2) : 119–132. Illus. 1962.—Cytological analyses of interspecific hybrids between H. gracilis (n = 2) and H. spinulosus ssp. australis (n = 8) indicate that ssp. australis is a segmental allotetraploid, derived from past hybridization between 2 taxa with chromosome numbers of n = 4. Analysis of hybrids between H. gracilis (n = 2) and H. ravenii (n = 4), a previously undescribed species, has shown that the chromosome segments of these 2 species are almost completely homologous. Differential contraction is suggested as the explanation for the disappearance in late pachytene of presumed non-homologous segments which were evident in some cells at early pachytene. The pairing relationship of gracilis and ravenii chromosomes at pachytene and later prophase I stages of meiosis indicates that gracilis has evolved from ravenii by an aneuploid reduction process similar to that described for Crepis. The close morphological relationship of the 2 species adds further support to this proposition. Data from the cytological analysis of both interspecific hybrids indicate that x = 4 is the basic chromosome number for the Blepharodon section of Haplopappus.     

THE CHROMOSOME RACES OF ZINNIA JUNIPERIFOLIA

A comparative study of the distribution, habitat, morphology and cytology of diploid (n = 10) and tetraploid races of Z. juniperifolia of the subgenus Diplothrix (COMPOSITAE-Heliantheae) was carried out to elucidate their relationships. There is a positive correlation between chromosome number and many floral and vegetative characters, including pollen size. Chiasmata frequency is about 0.63 and 0.62 per chromosome in the diploid and in the tetraploid respectively. Multivalents are common in the latter. Although attempts to obtain colchicine-induced tetraploids have failed, available morphological, cytological and chromatographic evidence indicate the tetraploid may be of autoploid origin. Alternative ancestries involving other species of the subgenus are discussed. Taxonomically the tetraploid is considered a race of Z. juniperifolia.