Corrected author citation for the combination aster section Biotia (Asteraceae)

The author citation for the combination Aster section Biotia is corrected to: DC. ex Torrey & Gray.     

Aster chusanensis (Asteraceae), a new species from Korea

Asterchusanensis is described and illustrated, and compared with its most closely related species,A. pseudoglehni andA. spathulifolius. This new species differs markedly from the latter two by its unequal inner and outer phyllaries, pubescent stem, leaves, and corolla tube, and ray florets partly in two series.     

Chromosome number determinations in Aster section Conyzopsis (Asteraceae)

Chromosome numbers forAster brachyactis, A. frondosus, andA. laurentianus were determined to be 2n=14. The latter two are the first documented records for these taxa. The basic chromosome number for sectionConyzopsis is confirmed asx=7.     

湖南菊科紫菀属—新种—吉首紫菀

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Floral sex ratios and gynomonoecy in Aster (Asteraceae)

Gynomonoecy is the sexual system in which female and bisexual flowers occur on the same plant. This system has received little attention despite the considerable work on other plant sexual systems in the past few decades. Our study examines one hypothesized advantage of having two flower types on a plant, namely that this arrangement permits flexibility in allocation of resources to male and female reproductive functions. We examined 16 species of Aster (Asteraceae), a genus of gynomonoecious, perennial herbs. Plants in this genus produce heads consisting of a whorl of female flowers around a cluster of bisexual flowers. Among field-grown plants we found no evidence that plant size, date, position of heads, rainfall, or shade influenced the proportion of female flowers. A series of greenhouse experiments likewise revealed no large or consistent effects of light, nutrients, or position of heads on the proportion of ray flowers. While floral ratios proved very stable in the face of environmental and physiological variables, they exhibited significant variation among plants and among sibships in most species. We conclude that the presence of two flower types in gynomonoecious asters is not advantageous in permitting flexibility in allocation of resources to male and female functions. We believe that the advantage of the female flowers in aster heads lies either in reducing pollen-pistil interference or in attracting pollinators.     

Inaccessible Biodiversity on Limestone Cliffs: Aster tianmenshanensis (Asteraceae), a New Critically Endangered Species from China

Aster tianmenshanensis G. J. Zhang & T. G. Gao, a new species of Asteraceae from southern China is described and illustrated based on evidence from morphology, micromorphology and molecular phylogeny. The new species is superficially similar to Aster salwinensis Onno in having rosettes of spatulate leaves and a solitary, terminal capitulum, but it differs by its glabrous leaf margins, unequal disc floret lobes and 1-seriate pappus. The molecular phylogenetic analysis, based on nuclear sequences ITS, ETS and chloroplast sequence trnL-F, showed that the new species was nested within the genus Aster and formed a well supported clade with Aster verticillatus (Reinw.) Brouillet et al. The new species differs from the latter in having unbranched stems, much larger capitula, unequal disc floret lobes, beakless achenes and persistent pappus. In particular, A. tianmenshanensis has very short stigmatic lines, only ca. 0.18 mm long and less than 1/3 of the length of sterile style tip appendages, remarkably different from its congeners. This type of stigmatic line, as far as we know, has not been found in any other species of Aster. The very short stigmatic lines plus the unequal disc floret lobes imply that the new species may have a very specialized pollination system, which may be a consequence of habitat specialization. The new species grows only on the limestone cliffs of Mt. Tianmen, Hunan Province, at the elevation of 1400 m. It could only be accessed when a plank walkway was built across the cliffs for tourists. As it is known only from an area estimated at less than 10 km² and a walkway passes through this location, its habitat could be easily disturbed. This species should best be treated as Critically Endangered based on the International Union for Conservation of Nature Red List Categories and Criteria B2a.     

Data on chromosome numbers in Aster (Asteraceae), with comments on the status and relationships of certain North American species

Chromosome counts are presented for more than 250 populations ofAster representing 56 species and eight spontaneous interspecific hybrids. Species are listed according to the infrageneric classification system presented in the preceding paper which utilizes basic chromosome numbers as the pivotal diagnostic character. Fundamental to the classification is an ecological species concept. The list is augmented by a series of comments on field observations and on the examination of types. Six older names previously placed in synonymy or recognized at an inferior rank are reinstated at the species level:A. brachypholis, A.firmus, A. fragilis, A. longifolius, A. simmondsii andA. tardiflorus. Two taxa included as species in current manuals of the eastern North American flora are reduced in status to subspecies rank underA. cordifolius. Putative hybrid status is assigned to four taxa previously treated and originally published as species:A. × coerulescens (= A. praealtus × A. simplex, A. × interior (= A. simplex × A. tradescantii, A. × maccallae (= A. ciliolatus × A. subspicatus) and A. × subgeminatus (= A. ciliolatus × A. tardiflorus). With new data available, the basic chromosome number ofx = 8 has now been confirmed for all species ofAster sectionHeterophylli, except the Mexican A.coahuilensis.     

Hamata,a new section ofTaraxacum (Asteraceae)

A distinct group of triploid, apomicticTaraxacum species, recognized by blackish green, pruinose involucres and ± hamate lateral lobes, is newly described as sectionHamata. Cytological and morphological investigations have shown a distinctive uniformity among these species which supports this classification. A key to all knownHamata species, illustrations and notes about critical species are given. A new species of the section,T. fusciflorum, is described.     

Bottleneck-induced dissolution of self-incompatibility and breeding system consequences in Aster furcatus (Asteraceae)

Aster furcatus is a rare species with extremely limited genetic variation at isozyme loci. We utilized crossing experiments and seed set data obtained from natural populations to verify that there is also little allelic variation at the self-incompatibility (S) locus. Seed set in several populations was limited by a low number of S-alleles. Associated with a low number of S-alleles in populations was the dissolution of the incompatibility system, manifest by individual variation in self-compatibility, and by complex dominance relationships among S-alleles. Plant self-compatibility was correlated with mean number of ovules per inflorescence. Thus, self-compatibility appeared to be under partial environmental influence. Computer simulations revealed that the shapes of seed set distribution curves of modeled self-incompatible plant populations depend on the number of incompatibility alleles in the populations. By varying the number of S-alleles in modeled populations, we generated seed set distribution curves similar to those of natural populations. Genetic bottlenecks reduce the number of S-alleles and the proportion of compatible matings in populations of multiallelic self-incompatible species. Self-compatible genotypes are at a selective advantage in populations that lack a sufficient number of S-alleles to produce compatible crosses. Aster furcatus appears to be evolving self-compatibility as a result of bottleneck-induced losses of S-alleles.     

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.     

Revision of the dioecious genus chersodoma phil. (Senecioneae,Asteraceae), including a new species and status change

A revision of the dioecious genus Chersodoma (Senecioneae, Asteraceae) recognizes nine species, including a new species, C. deltoidea Sagást. & M. O. Dillon, from northern Peru and a status change for a northwestern Argentine endemic, C. glabriuscula (Cabrera) M. O. Dillon & Sagást. Chersodoma is confined to the Andean Cordillera and is the only dioecious member of the Senecioneae in continental South America. A cladistic analysis of a morphological data set supports the monophyly of the genus and the recognition of two previously established subgenera. Subgenus Chersodoma contains three species (C. argentina, C. candida, C. jodopappa) with greatest diversity in the semi-arid puna of northwestern Argentina and adjacent Bolivia and Chile. Subgenus Diclinanthus B. Nord., contains six species (C. antennaria, C. arequipensis, C. deltoidea, C. juanisernii, C. glabriuscula, and C. ovopedata) with greatest diversity in Peru. A key to Andean genera of Senecioneae is provided. A discussion of species relationships and historical biogeography is presented as suggested by morphological parsimony analysis.     

Genetic diversity and hierarchical population structure of a rare autotetraploid plant,Aster kantoensis (Asteraceae)

We sampled 17 populations of a rare autotetraploid Aster kantoensis (Asteraceae) from three river systems located in central Japan, and studied them for allelic variation at 22 enzyme loci. There was no significant correlation between the actual population size and three genetic diversity parameters, suggesting that the effective population size was very small even for the large populations, i.e., even large populations may still have a high probability of being of recent origin and remain influenced by the founder effect. Compared to other autotetraploid species, the total genetic variation of A. kantoensis is small. The number of alleles and gene diversity of a population were not significantly different among the river systems, although the percentage of polymorphic loci was different. Genetic differentiation among river systems was larger than between populations within the river systems, thereby indicating that gene flow between river systems is small, especially between the Kinu River system and Tama or Sagami River systems.     

Genetic differentiation within and among island populations of the endangered plant Aster miyagii (Asteraceae), an endemic to the Ryukyu Islands

Genetic diversity was examined at 17 putative allozyme loci in 18 populations of the insular endemic plant Aster miyagii (Asteraceae). This species is geographically restricted to only three islands of the Ryukyu Islands and is on the federal list of threatened plants. Genetic differentiation within an island is small, suggesting that gene flow among populations on the same island is sufficiently large to prevent divergence. By contrast, genetic differentiation among islands is large, especially between Amamioshima Island and the other two islands, suggesting that gene flow between the islands is highly restricted. Two unique alleles are nearly fixed in populations on Amamioshima Island, which is the southernmost island of the three. Comparatively, genetic diversity is the smallest on Amamioshima Island. This genetic paucity on Amamioshima Island is probably a result of a population bottleneck at colonization or the small effective population size on this island. Genetic diversity at the species level of A. miyagii is larger than those of the species with a similar life history and of the congeneric widespread species, suggesting that the species has an old origin as an insular endemic species.     

Typification and synonymy of names in Santolina (Asteraceae: Anthemideae) published by Hoffmannsegg and Link

During recent studies in the Santolina rosmarinifolia L. aggregate, nomenclatural problems with the the names S. impressa and S. semidentata published by Hoffmannsegg and Link were revealed. Here, both names are neotypified and S. rosmarinifolia var. cinerea Pau & Merino and S. zamorana Losa are lectotypified. The criteria used to recognise S. impressa and S. semidentata and their diagnostic characters are discussed. Revision of the lectotypes of S. rosmarinifolia var. cinerea Pau & Merino and of S. zamorana Losa suggests that both names are synonyms of S. semidentata. The full synonymy of S. impressa and S. semidentata is provided.     

Dicoma hindana (Asteraceae), a new species from Somalia

Ortíz, S. & Oubiña, J.R. 1995. Dicoma hindana (Asteraceae), a new species from Somalia. - Nord. J. Bot. 15: 187–189. Copenhagen. ISSN 0107–055X.
A new species of the genus Dicoma (sect. Psilocoma ), from Somalia, is described. The characteristics by which it can be distinguished from related species are listed.     

Heliantheae sensu lato (Asteraceae), clades and classification

The interrelationships within theHeliantheae s. lato and the closely relatedEupatorieae are analyzed and discussed. The basis to this discussion is a cladistic analysis of 141 morphological characters (172 apomorphic states) scored for 97 genera. TheHeleniae s. lato, a subgroup of theHeliantheae s. lato, are paraphyletic, and a monophyletic group corresponding largely to theHeliantheae s. str. is recognized. TheEcliptinae sensuRobinson are polyphyletic. TheCoreopsidinae form an ingroup in theHeliantheae s. str. TheTageteae (Pectidinae) and theMadieae (Madiinae) are two separate branches within the helenioid assemblage of taxa.     

Erigeron salmonensis (Asteraceae), a rare new species from Idaho

Erigeron salmonensis, a diploid (n=9) species known only from one location in the Salmon River canyon of Idaho, is described and illustrated. The species appears to be most closely related toE. arenarioides, an endemic of northern Utah.Erigeron salmonensis differs in its long, naked, eglandular peduncles; longer leaves; smaller heads with fewer phyllaries; and longer, fewer ray florets. Federal Endangered or Threatened status may be warranted if additional populations are not discovered.     

Chromosome numbers and evolutionary patterns in the Aster Occidentalis (Asteraceae) polyploid complex of western North America

The 15 species studied have chromosome numbers predominantly based onx=8, and intraspecific polyploidy is frequent. The numbersx=13 andx=18 in two species are hypothesized to represent dibasic alloploidy rather than aneuploidy. The group forms a hybrid complex, with 11 basic diploids thus far discovered and with much morphological variation observed among species at the hexaploid and higher polyploid levels. Both alloploidy and introgression probably contribute to this pattern of variability. The known diploids are assigned to eight species, with the suggestion that further taxonomic division may be warranted as the group becomes better known. Seven recognized species exist only as polyploids. Because of their reticulate relationships, the polyploid populations form an extensively intergading series of morphological types. It is cautioned that excessive taxonomic splitting, based on minor polyploid variants, might lead to an unwieldy and impractical classification for the group.