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Two cytotypes of Lysimachia mauritiana collected from Japanese mainland (JM-type) and the Sakishima group (SR-type), located in the southernmost of the Ryukyu Archipelago of Japan, were cytoge- netically analyzed. JM- and SR-types showed karyotype formulae of 2n=20(4m)=4m+2sm+4st+10t and 2n=18(6m)=6m+2sm+10t, respectively. In FISH analysis, a signal of 5S rDNA was observed at the interstitial region of long arm on a pair of t-chromosome in both cytotypes. On the other hand, different sizes of 45S rDNA signals were observed on the distal and proximal regions of m-, sm-, st- and t-chromosomes in JM-type, and of m- and t-chromosomes in SR-type. Also in SR-type, a tiny 45S rDNA signal was shown at the interstitial region of long arm on sm-chromosome. Telomere signals in two cytotypes appeared at both ends of all chromosomes, and at internal sites of certain chromosomes. The big telomere sequence signal at the proximal region coincided with the small 45S rDNA signal in JM-type. These results gave us a fusion/fi ssion hypothesis with two st- or one m-chromosome(s) for new intraspecifi c karyotype formation of JM-type or SR-type.

Aneuploidy and karyotypic polymorphism in 98 individuals of Lysimachia mauritiana collected in middle and southern parts of the Ryukyu Archipelago, Okinawa Pref., were cytologically analyzed. Aneuploids of 2n=16, 17, 18, 19 and 20, and 13 cytotypes were recognized in the areas. By using longer metacentric chromosomes as markers, the number of all cytotypes in the Ryukyu Archipelago, Japan was 18, together with data reported earlier.

Diploid individuals (2n=18) of Chrysanthemum zawadskii, C. indicum and C. boreale, two or all three of which often occur together in the wild in East Asia, have diverse metaphase karyotypes. We hypothesised that the diverse karyotypes result from chromosome rearrangements. To test this, we investigated chromosomal behaviour during pollen mother cell (PMC) meiosis and pollen fertility, using 33 individuals collected from seven populations in Korea. All individuals contained one or two multivalents (mostly quadrivalents) at late prophase I and metaphase I in some PMCs (approximately 17–37%), and at least one or two bivalents composed of homologous chromosomes of different length and centromere position in all PMCs. This meiotic chromosomal behaviour indicates that chromosome rearrangements, i.e., reciprocal translocation and unequal crossing-over, are prevalent in Chrysanthemum species. Nevertheless, because of successful chromosome segregation in anaphase I and II, they produce ample stainable pollen with different chromosome complements. Fertilization by such gametes should result in diverse somatic karyotypes. We also discuss the possibility that older or relatively recent hybridization events have led to a high rate of irregular meiotic chromosome behaviours and pollen sterility, particularly in C. indicum.

Karyotype change of Lysimachia mauritiana was cytologically analyzed in 76 individuals collected in the northern and middle parts of the Ryukyu Archipelago in Kagoshima Prefecture, Japan. Sixteen cytotypes were recognized in the areas. At least, four long median- and six terminal-centromeric chromosomes were included in the chromosome complements of the individuals observed. Remarkable choromosomal polymorphism or karyotype variation was shown in the Ryukyu Archipelago, especially the Amami group.

Chromosome numbers and karyotypes of Corylopsis glabrescens and C. gotoana in the Hamamelidaceae were investigated. Corylopsis glabrescens was diploid with 2n=24=14m+8sm+2st, while C. gotoana was tetraploid with 2n=48=36m+8sm+4st. The karyotype of the diploid C. glabrescens was different from that of the diploid C. pauciflora previously reported in Japan, suggesting a heterogeneous origin of the two species. The karyotype of the tetraploid C. gotoana seemed to share a homogeneous karyotype composition with the hexaploid C. spicata previously reported in Japan.

† Background and Aims Investigating intraspecific karyotypic and genetic variations jointly can provide unique insights into how historical, ecological and cytogenetic factors influence microevolution. A coastal herb, Lysimachia mauritiana, exhibits extensive karyotypic polymorphism and displays a complex cytogeographic pattern across the Ryukyus. To explore whether a similar degree of chromosomal variation exists south of the Ryukyus, and in an attempt to ascertain the mechanisms that may have generated the patterns, comprehensive sampling was conducted in Taiwan. † Methods Karyotypes were analysed at mitotic metaphase for 550 individuals from 42 populations throughout Taiwan Proper and its adjacent islands. In addition, genetic variation was estimated using 12 allozymes (21 loci) of 314 individuals sampled from 12 localities. † Key Results Four chromosome numbers and eight cytotypes, including four endemic cytotypes, were detected. Cytotype distributions were highly structured geographically, with single cytotypes present in most populations and four major cytotypes dominating the north, east and south of Taiwan and the Penghu Archipelago. Allozyme variation was very low and F-statistics indicated an extremely high level of population differentiation, implying limited gene flow among populations. Cluster analysis of allozyme variation uncovered four geographic groups, each corresponding perfectly to the four dominant cytotypes. The geographic structure of cytotype distribution and allozyme variation probably resulted from severe genetic drift triggered by genetic bottlenecks, suggesting that Taiwanese populations were likely to be derived from four independent founder events. In the few localities with multiple cytotypes, cytogeographic patterns and inferences of chromosomal evolution revealed a trend of northward dispersal, consistent with the course of the Kuroshio Current that has been influential in shaping the coastal biota of the region. † Conclusions The data elucidate the patterns of colonization and the effects of the Kuroshio Current on the distribution of L. mauritiana in Taiwan. These inferences are highly relevant to other coastal plant species in the region and will stimulate further studies.

Summary Baum, D. A. & Oginuma, K.: A review of chromosome numbers in Bombacaceae with new counts for Adansonia. - Taxon 43: 11-20. 1994. - ISSN 0040-0262. New chromosome counts are reported for all eight species of Adansonia. The six Malagasy species and the Australian species have 2n = 88, whereas the single African species, A. digitata, has 2n = 160. We review published counts for the family as a whole and conclude that there have been many inaccurate counts but that 2n = 86-92 appears to be general. A. digitata, Rhodognaphalon brevicuspe and Eriotheca pubescens are inferred to be polyploids. The tribe Durioneae, with counts of 2n = 28 and 2n = 56, is distant from the remainder of the family, as also suggested by morphological, biogeographic and molecular data.

Published chromosome numbers in Sonneratia and Duabanga are inconsistent and indicate the basic numbers of the two genera are x = 9 or 11 and x = 12, respectively. Chromosome number counts made in this study for three species of Sonneratia indicate 2n = 24, and for two species of Duabanga, 2n = 48. The base is established as x = 12 in both genera. Although the genera have accumulated numerous autapomorphies that lead them to be regarded in separate subfamilies Sonneratioideae and Duabangoideae of the Lythraceae s.l., they share karyologically similar chromosomes and a unique basic number for the family, which is x = 8 in the remaining subfamilies Punicoideae and Lythroideae. Sonneratia and Duabanga are regarded as among the most primitive genera of the Lythraceae s.l. A number of other myrtalean higher taxa also have x = 12. This base number is most likely the ancestral number for the order.

† Background and Aims Farfugium (Asteraceae) is a small genus that contains the two species F. japonicum and F. hiberniflorum and is distributed along a long archipelago in east Asia. The common taxon, F. japonicum, includes three varieties associated with a wide range of habitats, including forest understorey (sciophytes), coastal crag (heliophytes) and riverbed (rheophytes). Leaf shape is an important taxonomic character within this genus and is associated with the habitat. † Methods Twenty populations that included all Farfugium taxa were collected throughout its range. Leaf morphology was measured to determine differences amongst the taxa. Phylogenetic analyses based on sequences of the internal transcribed spacer of nuclear rDNA and four plastid DNA regions (matK, trnL-trnF, trnH-psbA and rpl20-rps12) were conducted separately. † Key Results Leaf morphology was significantly different amongst taxa, but morphological variations were partly explained by adaptation to certain environmental conditions that each population inhabited. Molecular phylogenies for the nDNA internal transcribed spacer and cpDNA were consistent in classifying F. hiberniflorum and the Taiwanese var. formosanum, whilst suggesting polyphyletic origins for the rheophyte, sciophyte and heliophyte taxa. All samples from the southern Ryukyus (Japan) and Taiwan clustered into a monophyletic group, which corroborates the land configuration theory involving Quaternary land-bridge formation and subsequent fragmentation into islands. The incongruence between the two DNA datasets may imply traces of introgressive hybridization and/or incomplete lineage sorting. † Conclusions The occurrence of rheophyte, sciophyte and heliophyte plants within Farfugium may be attributable to their isolation on islands and subsequent adaptation to the riparian, coastal crag and forest understorey environments, following their migration over the Quaternary land-bridge formation along their distribution range. Nearly identical DNA sequences coupled with highly divergent morphologies amongst these taxa suggest that diversification was rapid.

We present the first report on the chromosome number of Strasburgeria robusta, which is confined to montane forests of New Caledonia and is the only known species in Strasburgeriaceae. The species has 2n = 500, which is an exceedingly high chromosome number in angiosperms. Within Crossosomatales, molecular evidence has indicated that S. robusta is sister to Ixerba brexioides, which is endemic to New Zealand and is the sole species in Ixerbaceae. Comparisons to the chromosome number of I. brexioides (2n = 50) support a close affinity between the two species because they share the base number x = 25. It is generally accepted that an increase in ploidy is associated with the origin of novel adaptations. A high level of polyploidy (20x with x = 25) may have allowed S. robusta to survive on a fragment of Gondwana by adapting to its ultrabasic substrate.

Baill. (Amborellaceae), which, based on multiple gene analyses, was recently identified as the first branch in the angiosperm evolution, has somatic chromosomes of 2n=26 (x=13). At metaphase all the chromosomes have centromeres at the median position. Chromosomes of one pair are longer than those of the 12 remaining pairs, and have a secondary or small constriction. Based on karyotype analysis, as well as a survey of chromosome numbers in two other earliest lineages (i.e., Nymphaeaceae and Illiciales), the x=13 of Amborella is likely to be derived from x=14. The hypothesis that x=7 is the original base number in the angiosperms was briefly discussed.