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Subseries Turnera comprises a polyploid complex with ploidy levels ranging from diploid (2n = 2x = 10) to octoploid (2n = 8x = 40). The use of fluorescent in situ hybridization greatly improved the knowledge of the karyotypes of Turnera species by detecting and mapping rDNA sites. Interspecific variability in the number of sites was detected, but not in correlation with the ploidy level. A chromosome pair with a strong hybridization signal was always visible and this signal corresponded to the secondary constriction detectable by conventional techniques. Genomic in situ hybridization experiments combined with information on meiotic pairing in species and interspecific hybrids revealed that homologies detected by molecular analysis are greater than those detected by chromosome pairing. This suggests that the formation of the allopolyploids could involve species more closely related than previously assumed. Despite the molecular affinity among the genomes, the meiotic pairing is probably controlled by specific genes that restrict homeologous pairing in polyploids.

The genusThlaspi L. s.l. comprises numerous segregate lineages, which have been recognized as single genera. One of these, Microthlaspi, represents one such segregate. It consists of morphologically similar annual species. The species have different ploidy levels (2x, 4x, 6x) and are usually summarized under the designation Thlaspi perfoliatum agg. The assumed ancestral diploid members of the species complex, Microthlaspi granatense (Boiss. & Reut.) F.K. Meyer, Microthlaspi umbellatum (Steven ex DC.) F.K. Meyer, and Microthlaspi natolicum (Boiss.) F.K. Meyer, are restricted to northwestern Africa, southeastern Spain and Turkey, northern Iran, and Lebanon. Microthlaspi perfoliatum (L.) F.K. Meyer is widely distributed all over Europe and shows three ploidy levels. Diploid M. perfoliatum is restricted to Middle Europe, whereas tetraploid and hexaploid M. perfoliatum are distributed all over Europe. Individual plants from 125 natural populations throughout the geographic range were analysed using chloroplast DNA (cpDNA) and nuclear ribosomal DNA (nrDNA) restriction site analysis. Within Microthlaspi, 31 cpDNA restriction site mutations, six nrDNA restriction site variations, and two length mutations in the IGS region of the nrDNA were found, and a molecular phylogeny of the species complex has been derived. Polymorphisms in molecular data partitioned cytotypes of M. perfoliatum. The geographical distribution patterns apparently reflect ancient speciation processes and postglacial vegetation history.Key words: chloroplast DNA, nuclear ribosomal DNA, Microthlaspi perfoliatum polyploid complex, molecular phylogeny, biogeography.

The Antennaria frieseana (Trautv.) Ekman polyploid complex has been evaluated on numerous occasions without concensus to either the taxa that should be included or their proper ranks. The purpose of this phenetic study was to present a taxonomy for the polyploid complex that is not only independent of a knowledge of chromosome number and reproductive biology but that concurrently reflects morphological variation associated with each. The rank of subspecies (A. frieseana ssp. frieseana and A. frieseana ssp. alaskana (Malte) Hultén) was accepted as the most appropriate level of circumscription that satisfied the purpose of the phenetic study and was supported by the analysis. These subspecies differ with respect to the length of the involucre, inner phyllary length, pappus length, corolla length (the latter subspecies being typically smaller than the former), chromosome number, reproductive biology, and (in part) provenance. Antennaria frieseana ssp frieseana is an agamospermous polyploid, represented by pentaploid (2n = 70) and hexaploid (2n = 84) cytotypes. Antennaria frieseana ssp. alaskana is sexual, probably partially agamospermous (tetraploid cytotype), and either diploid (2n = 28) or tetraploid (2n = 56). Key words: Antennaria frieseana, morphological variation, apomicts, sexual, agamospermy.

Taxa included in the Antennaria monocephala DC. polyploid complex were previously circumscribed at the specific, subspecific, or varietal levels without concensus. The purpose of this phenetic study was to construct a taxonomy that not only reflects the presumed evolutionary history of the complex but also presents a taxonomy that is both functional and informative, regardless of an individual's gender or more importantly, the reproductive mode of the population. The rank of subspecies (A. monocephala ssp. monocephala and A. monocephala ssp. angustata (Green) Hultén) was accepted as the most appropriate level of gender independent circumscription that satisfied the purpose of the phenetic study. These subspecies differ with respect to tomentum, chromosome number, reproductive biology, and (in part) provenance. The former taxon, A. monocephala ssp. monocephala, is a sexual diploid (2n = 28); the latter taxon, A. monocephala ssp. augustata, is an apomictic polyploid, with chromosome numbers ranging from tetraploid (2n = 56) to octoploid (2n = 112). In A. monocephala ssp. monocephala the adaxial surface of the basal and cauline leaves is glabrous-strigose, as is the stem. In A. monocephala ssp. angustata the adaxial surface of both basal and cauline leaves is floccose-tomentose, as is the surface of the stem. Key words: Antennaria monocephala polyploid complex, multivariate analyses.

The genus Chaetobromus consists of four, somewhat ill defined species. Morphological merging and the existence of intermediates render the separation of these species difficult. A basic chromosome number of x = 6 for Chaetobromus is substantiated by the presence of diploid specimens. The genus forms a polyploid complex, ranging from diploid to duodecaploid. Polyploidy occurs in the form of segmental alloploidy and occasionally as alloploidy. Meiotic abnormalities, in the form of univalents during metaphase I and anaphase laggards, were observed in some specimens. A cancerous growth form, involving the merging of different cells and the subsequent fusion of their nuclei, has been observed in two specimens, Spies 3366 and CW1. No apparent explanation could be found for this uncontrolled increase in ploidy level during microsporogenesis. Extensive morphological, anatomical, and cytogenetical variation exists in the genus, indicating hybridization and polyploidization. Numerical analysis of morphological data obtained from the specimens studied indicates two groups. Cytogenetic evidence supports the numerical analysis. In an attempt to resolve the contributor species to this polyploid hybrid swarm, attention should be given to the diploid representatives of the putative progenitor species.Key words: Chaetobromus, hybridization, meiosis, numerical taxonomy, polyploidy.

The Eurasian grass, Calamagrostis epigejos (L.) Roth, has been both deliberately and accidentally introduced to North America. Deliberate introductions have usually been destroyed because the plants were weedy and difficult to confine. Introductions at approximately 50 sites, most of them accidental, are documented. While the grass sometimes is the dominant species over several square metres and can out-compete some other weedy species, only at two sites is it known to have spread more than 10 km in a 30-year period. One site is Ontario, Canada, along the road between Espanola and Whitefish Falls, and the other is Liberty State Park in New Jersey, U.S.A. There have been major earth moving projects at both sites so that spread of rhizomes as well as seed dispersal may have been involved. Data analyses of 16 characters used, or possibly useful, in recognizing intraspecific taxa are presented. Taxonomic recognition of C. epigejos as an amphimictic, polyploid complex is discussed. Application of the treatment given by Tzvelev to our data suggests that (i) ssp. extremiorentalis Tzvelev and ssp. macrolepis (Litv.) Tzvelev have each been introduced once into North America; (ii) most specimens in North America belong to ssp. epigejos, ssp. glomerata (Boiss. and Buhse) Tzvelev, or ssp. meinshausenii Tzvelev, but it is not always possible to distinguish among these subspecies with confidence; and (iii) C. epigejos var. georgica (C. Koch) Ledeb., as recognized by Fernald, is probably synonymous with ssp. glomerata. Plants collected from five sites in Ontario had chromosome counts of 2n = 28 + 4B. Plants of C. epigejos ssp. macrolepis from New York were 2n = 42.

The isozymes for 10 enzyme systems were electrophoretically investigated in Stellaria longipes and Stellaria longifolia. Twenty-six isozymes were detected in S. longipes, 21 of which were found in S. longifolia. Twenty-six gene loci were inferred to control these isozymes; 19 were confirmed by selfing and crossing experiments. The intergenic relationships were examined among 34 pairs of genes. The genetic basis of isozymes was documented. Only four pairs of genes are inherited as linkage, and others were confirmed to be inherited independently.

Diploid (2n = 14) and tetraploid (2n = 28) entities in series Eubarbatae of the genus Avena have been found to be genetically closely linked and are regarded as a single polyploid complex. At both ploidy levels the various morphological types are interfertile. Diploids and tetraploids are largely sympatric in their distribution and converge considerably in their ranges of morphological variation. Contacts between diploids and tetraploids are common and blurred morphological boundaries characterize mixed populations.The possibility of gene flow between diploids and tetraploids has been indicated by the behavior of triploid F1 hybrids. Such hybrids have been found to be partially fertile. In their progeny a conspicuous restoration of fertility is apparent: numerous plants of the F2 generation have been stabilized around the tetraploid level, few around the diploid level. In contact areas, triploids can be regarded as efficient bridges of gene flow between the two ploidy levels.The range of variation found at the tetraploid level is fully explicable by the variation present in the diploid races. Tetraploids are therefore regarded to have had an inter-varietal origin, i.e. have evolved from a single genome. They apparently represent an extreme case of bivalentization, where a full shift from an autotetraploid to an allotetraploid meiotic behavior had occurred. Meiotic behavior of the F2 plants also indicate such origin.

The taxonomy of the Trifolium longipes Nutt. complex (Leguminosae) in the western United States is reviewed. This polyploid complex consists of diploid, tetraploid, and hexaploid races having a base number of x = 8. For the most part, each race occupies a distinct geographical area. Keys to the three species recognized in this study and to the 11 subspecies of T. longipes in the restricted sense are provided. For each taxon a description and synonymy are given. Maps of the chromosome races and taxonomic entities are appended.