Extensive chromosome number variation in Aster ageratoides var. pendulus (Asteraceae)

Aster ageratoides var. pendulus, a recently described taxon, is endemic to Mt Hupingshan of north‐western Hunan, China. Field observations and collections were made from the only known population. Root‐tip squashes were used to determine the chromosome numbers of 96 plants and 61 seedlings from the achenes of eight sample plants. The results show that var. pedulus is a swarm of 30 cytotypes with nearly continuous chromosome numbers from 2n = 60 to 2n = 92. Chromosome numbers of 61 seedlings vary from 2n = 61 to 2n = 91, belonging to 18 cytotypes. The chromosome number variation of var. pendulus is highly unusual not only in the A. ageratoides polyploid complex but also in angiosperms. Such an enormous continuous variation of chromosome numbers could have arisen by the combined effect of hybridization, recent origin and high levels of polyploidy. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 378–387.     

Chromosome and genome size variation in Luzula (Juncaceae), a genus with holocentric chromosomes

The present study examines chromosome and genome size evolution in Luzula (woodrush; Juncaceae), a monocot genus with holocentric chromosomes. Detailed karyotypes and genome size estimates were obtained for seven Luzula spp., and these were combined with additional data from the literature to enable a comprehensive cytological analysis of the genus. So that the direction of karyotype and genome size changes could be determined, the cytological data were superimposed onto a phylogenetic tree based on the trnL‐F and internal transcribed spacer (ITS) DNA regions. Overall, Luzula shows considerable cytological variation both in terms of chromosome number (2n = 6–66) and genome size (15‐fold variation; 2C = 0.56–8.51 pg; 547.7–8322.8 Mb). In addition, there is considerable diversity in the genomic mechanisms responsible, with the range of karyotypes arising via agmatoploidy (chromosome fission), symploidy (chromosome fusion) and/or polyploidy accompanied, in some cases, by the amplification or elimination of DNA. Viewed in an evolutionary framework, no broad trend in karyotype or genome evolution was apparent across the genus; instead, different mechanisms of karyotype evolution appear to be operating in different clades. It is clear that Luzula exhibits considerable genomic flexibility and tolerance to large, genome‐scale changes. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 529–541.     

Cytogenetic and molecular characterization of morphologically variable Sisyrinchium micranthum (Iridaceae) in southern Brazil

Sisyrinchium micranthum is native to southern Brazil and shows a wide range of morphological variation in this region. This study was performed to compare individuals of this species in terms of traits such as morphology, chromosome number, meiotic behaviour, pollen viability and genetic diversity using inter simple sequence repeat markers. First, general morphological aspects were evaluated and plants were classified into three morphological categories (CI, CII and CIII) to analyse the cytogenetic and genetic data. Three chromosome numbers corresponding to three ploidies were found: 2n = 2x = 16, 2n = 4x = 32 and 2n = 6x = 48. All morphological types showed regular meiotic behaviour and high meiotic index values and pollen viability. CII is the most frequent in southern Brazil. The most common haploid chromosome number, n = 8, has not been reported previously in this species. The percentage of polymorphic loci ranged from 6.45 to 61.29% for each accession. Molecular and cytogenetic analyses indicate that some S. micranthum accessions may have more than one ploidy. This study represents the first effort to characterize this taxonomically complex species based on cytogenetic and genetic aspects. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 350–364.     

Towards resolving the systematics of Cerastium subsection Cerastium (Caryophyllaceae): a cytogenetic approach

Analyses of mitotic chromosome numbers and nuclear DNA content were performed for 39 populations of 17 perennial Cerastium taxa from south‐eastern Europe. The DNA content ranged from 2C = 2.43 to 8.78 pg, revealing four ploidy levels corresponding to 4x (2n = 36), 8x, 12x and 16x. High‐polyploid cytotypes with a greater range of ploidy (up to 2n = 144) occur mostly in the central mountainous parts of the Balkan Peninsula. The chromosome number was determined for the first time for C. dinaricum (2n = 36 + 1B), C. decalvans subsp. orbelicum (2n = 36), C. decalvans subsp. glutinosum (2n = 36), C. neoscardicum (2n = 144), C. malyi subsp. serpentini (2n = 144) and C. moesiacum s.s. (2n = 144). New chromosome counts were recorded for C. arvense subsp. strictum (2n = 108), C. banaticum subsp. kosaninii (2n = 36) and C. grandiflorum (2n = 36). For the first time, flow cytometry was used to estimate C values for six species (15 taxonomic entities). The intraspecific variation quotient of C values is high, ranging from 1.003 in C. malyi to 1.306 in C. decalvans subsp. decalvans. The variation in chromosome size among both tetra‐ and octoploid members of Cerastium is much more prominent than in most other angiosperm polyploid series. Significant genome downsizing after polyploidization was observed in some investigated taxa. Differences in ploidy levels and monoploid genome size values confirm the taxonomic status of C. decalvans subsp. glutinosum and C. decalvans subsp. leontopodium. The results obtained indicate a possible close relationship between C. banaticum and C. grandiflorum, but not C. arvense. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 182 , 205–224.     

Chromosomal evolution in Pleurothallidinae (Orchidaceae: Epidendroideae) with an emphasis on the genus Acianthera: chromosome numbers and heterochromatin

In this study, we analysed chromosome number variation and chromomycin A₃/4′,6‐diamidino‐2‐phenylindole (CMA/DAPI) banding patterns in 48 species belonging to 12 genera of subtribe Pleurothallidinae (Orchidaceae) in order to understand the chromosome evolution based on recent phylogenetic hypotheses and taxonomic treatments. All species had small chromosomes, with numbers ranging from 2n = 20 in two Specklinia spp. to 2n = 80 in an unidentified Octomeria sp. In Acianthera, the most highly represented genus in this study, a great diversity of chromosome number and pattern of fluorescent bands was observed, showing heterochromatin accumulation in Acianthera section Sicariae subsection Pectinatae. Interspecific ascending and, mainly, descending dysploidy were the main mechanisms of chromosome number evolution in subtribe Pleurothallidinae. For Pleurothallidinae, x = 20 is suggested as the basic chromosome number, the same suggested for the related subtribe Laeliinae and for the whole tribe Epidendreae. The Brazilian species of the mega‐genus Stelis had chromosomes with small amounts of heterochromatin and chromosome numbers based on x₂ = 16. These are generally divergent from those reported for Andean and Meso‐American species, but in agreement with the monophyletic hypothesis proposed for Stelis spp. with a Brazilian Atlantic distribution. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 102–120.     

Comparative phylogenetic analysis reveals long‐term isolation of lineages on the Three Kings Islands,New Zealand

We have used comparative phylogenetic analysis to infer the age and biogeographical origins of the Three Kings Islands insect fauna, an archipelago only 56 km off the northern tip of New Zealand. We densely sampled six insect lineages (five Coleoptera, Brachynopus latus, Brachynopus scutellaris, Tarphiomimus spp., Epistranus lawsoni, and Syrphetodes spp., and one Phasmatodea, Pseudoclitarchus sentus) throughout New Zealand and sequenced mitochondrial DNA to assess phylogenetic relationships and determine ages of haplotype lineages on the Three Kings Islands. We recovered two biogeographical patterns. The first pattern was seen in three taxa, B. latus, Syrphetodes spp., and E. lawsoni, which had sister group relationships between the Three Kings and the adjacent North Cape region at the very northern tip of New Zealand. The second pattern, inferred in P. sentus, B. scutellaris, and Tarphiomimus spp., was where Three Kings lineages had sister groups that were widespread throughout most or all of New Zealand. The divergence dates, estimated using a range of previously estimated substitution rates, ranged from as old as 24 Mya in B. scutellaris to as young as 2.24 Mya in Tarphiomimus. These results are consistent with continual emergent land on the Three Kings Ridge since at least the Miocene and a lack of land connections between the Three Kings Islands and mainland New Zealand during Pleistocene sea‐level lowering. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 361–377.     

Karyology of the genus Epidendrum (Orchidaceae: Laeliinae) with emphasis on subgenus Amphiglottium and chromosome number variability in Epidendrum secundum

Epidendrum is one of the largest Neotropical genera of Orchidaceae and comprises approximately 1500 species. Only 2.8% of these species have been studied cytologically, demonstrating chromosome numbers ranging from n = 12 in E. fulgens to n = 120 in E. cinnabarinum. The present work evaluated the evolution of the karyotypes of Epidendrum spp. based on data gathered from the literature and from analyses of the karyotypes of 16 Brazilian species (nine previously unpublished). The appearance of one karyotype with n = 12 with one larger chromosome pair in subgenus Amphiglottium appears to have occurred at the beginning of the divergence of this lineage, and x = 12 probably represents the basic number of this subgenus. Epidendrum secundum exhibits wide variation in chromosome numbers, with ten different cytotypes found in 22 Brazilian populations, seven of which were new counts: 2n = 30, 42, 50, 54, 56, 58 and 84. Most lineages of Epidendrum seem to have been secondarily derived from one ancestral stock with x = 20, as is seen in the majority of the present‐day representatives of the genus. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172 , 329–344.     

Ploidy in the alpine sedge Kobresia pygmaea (Cyperaceae) and related species: combined application of chromosome counts,new microsatellite markers and flow cytometry

Polyploidy is a fundamental mechanism in evolution, but is hard to detect in taxa with agmatoploidy or aneuploidy. We tested whether a combination of chromosome counting, microsatellite analyses and flow cytometric measurements represents a suitable approach for the detection of basic chromosome numbers and ploidy in Kobresia (Cyperaceae). Chromosome counting resulted in 2n = 64 for Kobresia pygmaea and K. cercostachys, 2n = 58 and 64 for K. myosuroides, and 2n = 72 for K. simpliciuscula. We characterized eight microsatellite loci for K. pygmaea, which gave a maximum of four alleles per individual. Cross‐species amplification was tested in 26 congeneric species and, on average, six of eight loci amplified successfully. Using flow cytometry, we confirmed tetraploidy in K. pygmaea. Basic chromosome numbers and ploidy were inferred from chromosome counts and the maximum number of alleles per locus. We consider the basic numbers as x = 16 and 18, with irregularities derived from agmatoploidy and aneuploidy. Across all Kobresia taxa, ploidy ranged from diploid up to heptaploid. The combination of chromosome counts and microsatellite analyses is an ideal method for the determination of basic chromosome numbers and for inferring ploidy, and flow cytometry is a suitable tool for the identification of deviating cytotypes. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 22–35.     

Divergent genome sizes reflect the infrafamilial subdivision of the neotropical woody Marcgraviaceae

Neotropical Marcgraviaceae comprise about seven genera and 130 species of lianas and shrubs. They predominantly occur in lowland or montane rainforests and are characterized by a variety of pollination systems. Early classifications subdivided Marcgraviaceae into subfamilies Marcgravioideae and Noranteoideae, a concept supported by molecular data. Using flow cytometry and chromosome numbers, we investigated the role of genome size and polyploidization in the evolution of Marcgraviaceae and how genome sizes are distributed between the proposed infrafamilial groups. To do this we determined genome sizes and chromosome counts for six genera and 22 species for the first time. Our study supports the subfamilial classification of the family, revealing contrasting genome sizes in Noranteoideae (2C = 5.5–21.5 pg) and Marcgravioideae (2C = 2.3–6.2 pg). Polyploidy is considered to be the main source of genome size variation as in each subfamily the higher nuclear DNA amounts were associated with higher ploidy. In addition, genome size changes independent of polyploidy were also observed in some genera, suggesting an additional role for changes in repetitive DNA abundance in the evolution of Marcgraviaceae. A high chromosome base number (x = 18; 2n = 36 to ～70) points to an undetected lower diploid level or to palaeopolyploidy. Marcgraviaceae show a remarkable (nine‐fold) variation in genome size, and several Noranteoideae have genome sizes among the highest reported for tropical woody angiosperms worldwide. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 1–14.     

The vanishing clone: karyotypic evidence for extensive intraclonal genetic variation in the peach potato aphid,Myzus persicae (Hemiptera: Aphididae)

Analysis of holocentric mitotic metaphase chromosomes of the peach‐potato aphid Myzus persicae (Sulzer) clone 33H revealed different chromosome numbers, ranging from 12 to 17 within each embryo, in contrast to the standard karyotype of this species (2n = 12). Chromosome length measurements revealed that the observed chromosomal mosaicism is the result of recurrent fragmentations of chromosomes X, 1 and 3 because of fragile sites or hot spots of recombination. Fluorescent in situ hybridization experiments showed that X chromosomes were frequently involved in recurrent fragmentations, in particular their telomeric end opposite to the nucleolar organizer region. Experiments to induce males showed that M. persicae clone 33H is obligately parthenogenetic. The reproduction by apomictic parthenogenesis, together with a high telomerase expression that stabilized the chromosomes involved in the fragmentations observed in the M. persicae clone 33H, appears to favour the stabilization of the observed chromosome instability. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 350–358.     

Chromosome numbers and DNA content in Bromeliaceae: additional data and critical review

For the large Neotropical plant family Bromeliaceae, we provide new data on chromosome numbers, cytological features and genome size estimations, and combine them with data available in the literature. Root‐tip chromosome counts for 46 species representing four subfamilies and a literature review of previously published data were carried out. Propidium iodide staining and flow cytometry were used to estimate absolute genome sizes in five subfamilies of Bromeliaceae, sampling 28 species. Most species were diploid with 2n = 50 in Bromelioideae, Puyoideae and Pitcairnioideae, followed by 2n = 48 observed mainly in Tillandsioideae. Individual chromosome sizes varied more than tenfold, with the largest chromosomes observed in Tillandsioideae and the smallest in Bromelioideae. Genome sizes (2C‐values) varied from 0.85 to 2.23 pg, with the largest genomes in Tillandsioideae. Genome evolution in Bromeliaceae relies on two main mechanisms: polyploidy and dysploidy. With the exception of Tillandsioideae, polyploidy is positively correlated with genome size. Dysploidy is suggested as the mechanism responsible for the generation of the derived chromosome numbers, such as 2n = 32/34 or 2n = 48. The occurrence of B chromosomes in the dysploid genus Cryptanthus suggests ongoing speciation processes closely associated with chromosome rearrangements. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 349–368.     

A plant culture (BY‐2) widely used in molecular and cell studies is genetically unstable and highly heterogeneous

Nicotiana tabacum (tobacco, 2n = 4x = 48) is an allotetraploid with 24 S‐genome chromosomes (from a diploid related to N. sylvestris) and 24 T‐genome chromosomes (from a diploid related to N. tomentosiformis). The BY‐2 suspension cell culture, derived from N. tabacum cultivar Bright Yellow 2, has been used extensively for research in molecular and cell biology for almost 40 years; a Web of Knowledge search reveals that it has been used over 150 times since 2008 alone, largely for cell cycle and plant physiology studies. However, we show that this culture is unstable and, as with other long‐term cultures, exists as a community of cells with different karyotypes reflected in different chromosome numbers, morphologies and distributions of satellite repeats, At least one rearranged chromosome type was found in all cells investigated in detail. In comparison with N. tabacum, one satellite repeat, NTRS, has become dispersed across several chromosomes and there is complete homogenization of 35S rRNA genes towards T‐genome type rDNA units. Karyotype divergence should be considered when using BY‐2 cells for plant physiology or cell cycle/development studies in the future. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 459–471.     

Chromosome studies in Orchidaceae: karyotype divergence in Neotropical genera in subtribe Maxillariinae

Here, we study karyotype divergence in the closely related genera Brasiliorchis, Christensonella and Trigonidium belonging to subtribe Maxillariinae of subfamily Epidendroideae (Orchidaceae). We compare karyotypes in 15 species by (1) measuring 1C genome sizes, (2) mapping the distribution of 4′,6‐diamidino‐2‐phenylindole and chromomycin A3 chromosome bands and (3) localizing 5S and 45S nuclear ribosomal DNA (rDNA) sequences using fluorescent in situ hybridization. Recently, phylogenetic studies have been conducted to resolve species and genera relationships in subtribe Maxillariinae. We used these phylogenetic trees to map the cytogenetic characters in an evolutionary framework. This has enabled a better understanding of the patterns of genomic divergence in the group. Genome sizes range from 1C = 1.85 to 4.1 pg. The largest, B. schunkeana, shows evidence of genome upsizing, probably through the acquisition of tandem repeats that now form large 4′,6‐diamidino‐2‐phenylindole‐positive blocks of heterochromatin. Our cytogenetic data are consistent with a base chromosome number of 2n = 40, although Christensonella is characterized by a dysploid reduction in chromosome number to 2n = 36. The number of 5S and 45S rDNA sites is variable between species, consistent with high rates of karyotype divergence. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 29–39.     

Polyploidy and new chromosome counts in Helichrysum (Asteraceae,Gnaphalieae)

Mitotic chromosome numbers are reported for 31 populations representing 28 taxa of Helichrysum. Twelve are new and eight others provide confirmation of a unique previous reference. A new chromosome number, 2n = 42, is reported for H. odoratissimum. Polyploidy is confirmed as the most significant evolutionary trend in chromosome number within the genus. Chromosome data agree with trends observed in phylogenetic studies: a South African and diploid origin of the genus, followed by a radiation and diversification in southern Africa and several migrations towards the north of the African continent, the Mediterranean basin and Asia. Expansion and diversification of the genus have been accompanied by several genome duplications which have led to the acquisition of the tetraploid, hexaploid and octoploid levels, all in several independent events. Both autopolyploidy and allopolyploidy are suggested as probable speciation agents within the genus. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 511–521.     

New chromosome numbers, meiotic behaviour and pollen fertility in American taxa of Lupinus (Leguminosae): contributions to taxonomic and evolutionary studies

Original chromosome determinations are presented for 20 American Lupinus taxa, including, for the first time, unifoliolate species, together with first data on meiotic behaviour and pollen fertility for some South American species. Most of the Brazilian multifoliolate L. lanatus, L. rubriflorus, L. multiflorus, L. paranensis, L. bracteolaris and L. reitzii and unifoliolate L. crotalarioides, L. guaraniticus and L. velutinus accessions analysed presented regular chromosome pairing. Meiotic indexes and estimations of pollen viability were higher than 90% for all species and accessions analysed, reflecting the generally regular meiotic behaviour of these plants. Chromosome numbers were determined for the first time for the eastern South‐American species L. guaraniticus, L. crotalarioides, L. paranensis, L. paraguariensis and L. velutinus (n = 18 or 2n = 36) and for the Andean L. ballianus, L. eanophyllus, L. huaronensis, L. semperflorens, plus another eight taxa (2n = 48) from Peru and Bolivia, and L. bandelierae (2n = 36) from Bolivia. Chromosome numbers were confirmed for L. lanatus, L. rubriflorus (2n = 36), L. bracteolaris (2n = 34) and L. microphyllus (2n = 48). In the three accessions of the North American unifoliolate species, L. cumulicola and L. villosus, a chromosome number (2n = 52) previously unknown among American taxa was found. The results of the study, plus published data, support the suggestions that south‐eastern South American species are a group cytologically differentiated from the Andean as well as from most other American ones, and that the Brazilian and the North American unifoliolate Lupinus had independent origins. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150 , 229–240.     

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.     

Cytogeography of European perennial species of Cyanus (Asteraceae)

To reveal the general cytogeographical pattern of Cyanus section Protocyanus in Europe, DNA ploidy and/or chromosome numbers were newly examined for 160 populations by flow cytometry (450 plants) and/or chromosome counting (30 plants). Furthermore, previously published karyological data were revised (236 records). Our analyses confirmed chromosome counts of 2n = 22 for all newly investigated samples of the C. triumfetti group (the records for C. semidecurrens and C. ternopoliensis are new), C. diospolitanus and C. achtarovii; 2n = 44 for C. montanus and C. mollis; and 2n = 20 for C. lingulatus, C. napulifer, C. nissanus, C. orbelicus, C. thirkei, C. tuberosus and C. velenovskyi. The chromosome count of 2n = 20 is the first report for C. epirotus. The cytotype 2n = 40 was newly recorded for the Crimean endemic C. fuscomarginatus and Calabrian and Greek populations of C. graminifolius. The cytotypes 2n = 20 and 2n = 40 were confirmed for C. pindicola. For the first time triploidy (2n～3x～30) was found in C. nissanus, C. thirkei and in a newly discovered hybrid, C. epirotus × C. graminifolius. Two contrasting ecogeographical patterns emerged: cytotypes derived from the base chromosome number x = 11 (2n = 22, 44) are widespread in northern latitudes and ecologically diverse, whereas cytotypes with x = 10 (2n = 20, 30, 40) are confined to mountains in southern Europe. In general, tetraploids have smaller ranges than diploids. The new combinations Cyanus section Protocyanus (Dobrocz.) Ol?avská comb. nov. and Cyanus ternopoliensis (Dobrocz.) Ol?avská comb. nov. are provided. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 230–257.     

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).     

Chromosomal studies on Coscoroba coscoroba (Aves: Anseriformes) reinforce the Coscoroba–Cereopsis clade

The Coscoroba (Coscoroba coscoroba), endemic to southern South America, is traditionally considered as an early branch from the common ancestor leading to true geese and swans. Recently, an interesting association between the Coscoroba and Cape Barren goose (Cereopsis novaehollandiae) as sister groups has been proposed. We present here the characterization of the karyotype of C. coscoroba using whole chromosome probes derived from Gallus gallus macrochromosomes. Our data showed that C. coscoroba has the highest diploid number among Anseriformes (2n = 98), and the conservation of macrochromosome pairs 1–10 indicates that the increase in diploid number has occurred by fission events involving only the microchromosomes. Moreover, the similarity between the diploid numbers of C. coscoroba (2n = 98) and Cereopsis novaehollandiae (2n = 92) reinforces the phylogenetic position of these two species as sister groups, considering that other species of geese and swans have diploid numbers close to 2n = 80. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 274–279.     

Cytological studies on the eastern Asian family Trochodendraceae

The somatic chromosome numbers for Trochodendron and Tetracentron were determined as 2n = 38 from shoot tip cells, from cultivated plants introduced from three places in Japan and southwest China. This number is consistent with one of the only two previous studies on the two genera and adds support for their membership of a distinct family Trochodendraceae. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 332–335.