A comparative study of cycad mucilages

The patterns of monosaccharide distribution of the mucilages of Cycadales are characteristic at the generic level. Arabinose, fucose, galactose, mannose, rhamnose and methylrhamnose were identified in the hydrolysed mucilage of Bowenia, Ceratozamia, Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas and Zamia. Stangeria contains no rhamnose and methylrhamnose, and Ceratozamia contains galactose only in traces. American genera may easily be distinguished from the others by means of their different monosaccharide composition. Lepidozamia appears to be well separated from Macrozamia.     

OBSERVATIONS ON PTYXIS,PHENOLOGY, AND TRICHOMES IN THE CYCADALES AND THEIR SYSTEMATIC IMPLICATIONS

Ptyxis, phenology, and leaf trichomes are described for 43 species representing all ten genera in the Cycadales. The typical annual growth sequence is: leaf flush production, cataphyll production, reproductive production, and finally cataphyll production in all taxa except Stangeria which does not have cataphylls and produces leaves one at a time throughout the year. The leaf and cataphyll bases are slightly winged except in Zamia and Ceratozamia, which have well developed stipules, and in Stangeria, which has a distinctive adaxial, stipular hood on the leaf bases. Longitudinal ptyxis of the whole leaf is of four types: circinate (only in Bowenia); erect (Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas, and some Zamia spp.); inflexed (Stangeria, Ceratozamia, and some Zamia spp.); and reflexed (rarely found in Cycas and Dioon). The pinnae are oriented so that the horizontal ptyxis is conduplicate in all taxa except Bowenia and Cycas where it is involute. The individual pinnae are circinate in Bowenia and Cycas, conduplicate in Stangeria, and flat in all other taxa. The pinnules of Bowenia are also flat. Leaf trichomes are of six types: transparent unbranched; transparent branched; colored unbranched; colored branched; colored idioblastic; and short colored curved. Cycas has only transparent branched (unequally) and unbranched. Ceratozamia, Dioon, Encephalartos, and Stangeria have transparent and colored trichomes, both unbranched. Bowenia, Lepidozamia and Macrozamia have short colored curved hairs and transparent unbranched hairs. Macrozamia is the only taxon with colored idioblastic trichomes. Zamia and Microcycas have transparent and colored hairs. Both trichome types occur branched and unbranched. Because of its decompound leaf, circinate ptyxis, cones on short determinate branches and other distinct characters the family Boweniaceae D. Stevenson fam. nov. is described. This family contains one genus: Bowenia.     

SYSTEMATIC STUDIES ON THE MEXICAN ZAMIACEAE. I. CHROMOSOME NUMBERS AND KARYOTYPES

Chromosome numbers and karyotypes are reported for seven species in three genera, of Mexican cycads. Karyotypic analysis of Cycads is made difficult by differential contraction, of their large chromosomes but idiograms are presented. Satellite variation is reported for three species of Ceratozamia. No satellites are reported for the three species of Zamia.     

Molecular systematic studies in cycads: Evidence fromtrnL Intron and ITS2 rDNA sequences

The results of a pilot DNA sequencing study of cycads conducted at the new molecular systematics laboratory at Fairchild Tropical Garden are presented and assessed with reference to previous phylogenetic analyses and classification schemes based on morphology and anatomy. Two DNA regions were sequenced and analyzed for variation, an intron in the trriL gene in the chloroplast genome (trriL intron) and the internal transcribed spacer region between the 5.8S and 26S ribosomal DNA subunits (ITS2). The trnL intron proved to be relatively conservative among cycad genera, while the ITS2 region contained higher levels of variation. Parsimony analysis of the sequences suggests a number of relationships, some of which were inferred by previous morphological studies, some of which are new. The sequences ofCycas are the most divergent among cycads, suggesting the longest isolation.Dioon is relatively isolated from the other genera and contains two major clades.Stangeria does not appear closely related toBowenia but does seem to have a weak affinity withZamia andMicrocycas. Lepidozamia is more closely related toEncephalartos than toMacrozamia. Sequence variation among the species ofCeratozamia is low.Microcycas andZamia are closely related.     

COMPARATIVE POLLEN MORPHOLOGY AND TAXONOMIC AFFINITIES IN CYCADALES

Scanning and transmission electron microscopy of pollen grains of 29 species, representing the ten extant genera of Cycadales, has provided valuable insight into their relationships. Pollen grains of these taxa are boat-shaped, monosulcate, and bilaterally symmetrical. They range from narrowly to widely elliptical or subcircular when viewed distally, and have an exine surface of psilate, foveolate, or fossulate. Pollen wall ultrastructure of Cycadales is typically tectate with alveolate∗∗∗spongy exine. The nexine is laminated in all genera. Nexine 1 (footlayer) is present in most species as a thin and often discontinuous layer. There is consistent variation in thickness of the sporoderm layers among the genera but relative uniformity within them. Pollen characteristics are well correlated with macro- and micromorphological features, chromosome numbers, geographical distribution, and postulated pollination mode. A close affinity between Encephalartos, Lepidozamia, and Macrozamia is recognized. Pollen characteristics of the genus Bowenia show some similarity with those of the latter group. Except for two species of Macrozamia which are narrowly elliptic, all of the genera have widely elliptic pollen and share a psilate exine surface and the thinnest sexine with nearly identical arrangement of alveoli. Pollen grains of the species in the genus Dioon exhibit a unique morphology but are more similar to Stangeria than they are to those of taxa in Zamiaceae. The circular outline of the grains and the foveolate exine surface are characters shared by these two genera, but several morphological features distinguish Dioon from Stangeria. Ceratozamia and Zamia share a widely elliptic shape, foveolate exine surface and nearly identical sexine, as well as morphological features and chromosome numbers. They differ from Microcycas in sexine thickness, gross morphology and chromosome numbers. The pollen grains of Cycas circinalis and C. revoluta differ in size and structure of the sexine from all other genera and from each other, substantiating their distinct subgeneric delimitations.     

A character‐based approach in the Mexican cycads supports diverse multigene combinations for DNA barcoding

A DNA barcoding study was conducted to determine the optimal combination of loci needed for successful species‐level molecular identification in three extant cycad genera—Ceratozamia, Dioon, and Zamia—that occur in Mexico. Based on conclusions of a previous multigene study in representative species of all genera in the Cycadales, we tested the DNA barcoding performance of seven chloroplast coding (matK, rpoB, rpoC1, and rbcL) and non‐coding (atpF/H, psbK/I, and trnH‐psbA) regions, plus sequences of the nuclear internal transcribed spacer. We analysed data under the assumptions of the “character attributes organization system” (CAOS), a character‐based approach in which species are identified through the presence of ‘DNA diagnostics’. In Ceratozamia, four chloroplast regions and one nuclear region were needed to achieve > 70% unique species identification. In contrast, the two‐gene combination atpF/H + psbK/I and the four‐gene combination atpF/H + psbK/I + rpoC1 + ITS2 were needed to reach 79% and 75% unique species identification in Dioon and Zamia, respectively. The combinations atpF/H + psbK/I and atpF/H + psbK/I + rpoC1 + ITS2 include loci previously considered by the international DNA barcoding community. However, none of the three combinations of potential DNA barcoding loci found to be optimal with a character‐based approach in the Mexican cycads coincides with the ‘core barcode’ of chloroplast markers (matK + rbcL) recently proposed for universal use in the plant kingdom.     

Karyotype evolution by centromeric fission inZamia (Cycadales)

The chromosome numbers of several species ofZamia from Mexico are reported.Z. paucijuga, distributed from central Oaxaca to Nayarit, has been found to have 2n = 23, 25, 26, 27 and 28. 2n = 28 is the highest chromosome number yet found in the cycads. Karyotypes of this species differ principally in the number of telocentric and metacentric chromosomes present in each; 2n = 23, 25, 26, 27 and 28 were found to have 5, 3, 2, 1 and 0 metacentric and 8, 12, 14, 16 and 18 telocentric chromosomes, respectively.Z. fischeri has been found to be 2n = 16,Z. furfuracea andZ. loddigesii 2n = 18.Zamia paucijuga on the basis of morphological and ecological characteristics, is considered to be an advanced member of this genus. Chromosome and karyotype evolution inZ. paucijuga may have occurred by centromeric fission of metacentric chromosomes; the karyotypes ofZ. paucijuga are strongly asymmetrical, suggesting that they evolved recently.     

A chemotaxonomic study of mucilages in American Zamiaceae

Abstract

Methylrhamnose, fucose, rhamnose, mannose, arabinose, galactose, and glucuronolactone are the monosaccharides identified in hydrolysed mucilages collected from 37 species belonging to the five American cycad genera (Ceratozamia, Chigua, Dioon, Microcycas and Zamia). The patterns of monosaccharide distribution in the mucilages resulted to be typical at the generic level, with the exception of Chigua and Zamia the patterns of which were similar. No differences appeared among species within single genera, with the exception of Zamia in which minor differences were observed at the intrageneric level. Differences and similarities among patterns at both intergeneric and intrageneric levels are discussed for their systematic implications.     

Chromosome phylogeny of <Emphasis Type="Italic">Zamia</Emphasis> and <Emphasis Type="Italic">Ceratozamia</Emphasis> by means of Robertsonian changes detected by fluorescence <Emphasis Type="Italic">in situ</Emphasis> hybridization (FISH) technique of rDNA

 Appearance and location of 45S rDNA and 5S rDNA signals were compared in chromosomes of nine species of the aneuploid Zamia and their taxonomically and phylogenetically closely related Ceratozamia mexicana. The 45S rDNA signal was detected in the proximal region of six chromosomes in Zamia angustifolia, Z. integrifolia, Z. pumila and Z. pygmaea (all 2n=16); in the proximal region of 6–14 chromosomes in Z. furfuracea, Z. loddigesii, Z. skinneri and Z. vazquezii (all 2n=18); and on the proximal region of 20 chromosomes in Z. muricata (2n=23). The 5S rDNA signals were commonly seen near the terminal region of the short arm of two metacentric chromosomes in the four species with 2n=16 and Z. furfuracea, Z. loddigesii and Z. vazquezii with 2n=18. Other 5S rDNA signals were seen near the terminal region of two terminal-centromeric chromosomes in Z. skinneri and near the terminal region of a metacentric and a telocentric chromosomes in Z. muricata. In contrast, those with 45S and 5S rDNA signals were exhibited in chromosomes of Ceratozamia mexicana in a different manner from those in the nine species of Zamia; the 45S rDNA signal in the terminal region of four metacentric and two submetacentric chromosomes and the 5S rDNA signal near the proximal region of two metacentric chromosomes. Received November 1, 1999 Accepted January 10, 2001     

Karyotypes of some species of the genus Lessingianthus (Vernonieae,Asteraceae) and taxonomic implications

We determined the karyotypes of nine species of Lessingianthus, eight of which are here analyzed for the first time. The results include the first chromosome count for L. plantaginoides, which is tetraploid with 2n = 64. All species showed a high proportion of metacentric chromosomes combined with a lower proportion of submetacentric pairs. Only L. coriaceus had a subtelocentric chromosome pair. B chromosomes were observed in L. coriaceus and L. varroniifolius, which were subtelocentric. Differences among the karyotypes of the studied species were small, suggesting that karyotype diversity in the genus evolved by small changes in the structure of chromosomes. Karyotype features appear useful to distinguish Lessingianthus from the closely related genera Chrysolaena and Lepidaploa.     

Phylogeny of the cycads based on multiple single-copy nuclear genes: congruence of concatenated parsimony,likelihood and species tree inference methods

Background and aims

Despite a recent new classification, a stable phylogeny for the cycads has been elusive, particularly regarding resolution of Bowenia, Stangeria and Dioon. In this study, five single-copy nuclear genes (SCNGs) are applied to the phylogeny of the order Cycadales. The specific aim is to evaluate several gene tree–species tree reconciliation approaches for developing an accurate phylogeny of the order, to contrast them with concatenated parsimony analysis and to resolve the erstwhile problematic phylogenetic position of these three genera.

Methods

DNA sequences of five SCNGs were obtained for 20 cycad species representing all ten genera of Cycadales. These were analysed with parsimony, maximum likelihood (ML) and three Bayesian methods of gene tree–species tree reconciliation, using Cycas as the outgroup. A calibrated date estimation was developed with Bayesian methods, and biogeographic analysis was also conducted.

Key Results

Concatenated parsimony, ML and three species tree inference methods resolve exactly the same tree topology with high support at most nodes. Dioon and Bowenia are the first and second branches of Cycadales after Cycas, respectively, followed by an encephalartoid clade (Macrozamia–Lepidozamia–Encephalartos), which is sister to a zamioid clade, of which Ceratozamia is the first branch, and in which Stangeria is sister to Microcycas and Zamia.

Conclusions

A single, well-supported phylogenetic hypothesis of the generic relationships of the Cycadales is presented. However, massive extinction events inferred from the fossil record that eliminated broader ancestral distributions within Zamiaceae compromise accurate optimization of ancestral biogeographical areas for that hypothesis. While major lineages of Cycadales are ancient, crown ages of all modern genera are no older than 12 million years, supporting a recent hypothesis of mostly Miocene radiations. This phylogeny can contribute to an accurate infrafamilial classification of Zamiaceae.     

CHROMOSOME MORPHOLOGY IN THE GENUS SAMBUCUS

Two basic chromosome karyotypes were found in the genus Sambucus. Chromosome numbers were observed to be 2n = 38 for S. callicarpa, S. cerulea, S. glauca, S. kamtschatica, S. melanocarpa, S. mexicana, S. miquelli, S. sibirica, and S. sieboldiana and 2n = 36 for S. simpsonii and S. williamsii. Measurements of 18 karyotypes are presented. The major differences between the two basic chromosome karyotypes can be explained as the result of a mis-division of a metacentric chromosome giving rise to two telocentric chromosomes, thus reducing the number of metacentrics from five to four and increasing the chromosome number from 2n = 36 to 2n = 38. Observed chromosome aberrations and aneuploidy may result from unstable telocentric chromosomes.     

CYTOLOGICAL ANALYSIS OF ANTHURIUM ANDRAEANUM (ARACEAE), ITS RELATED TAXA AND THEIR HYBRIDS

Karyotypes and meiotic configurations of Anthurium andraeanum and closely related taxa were analyzed. The karyotypes of A. andraeanum, A. caperatum, A. formosum, A. kamemotoanum, A. lindenianum, A. roseospadix, A. cf. sanctifidense, A. subsignatum, A. garagaranum, and an unidentified Anthurium sp. commonly consisted of four large metacentric or submetacentric chromosomes, two fairly large acrocentric chromosomes, two satellite chromosomes, and 22 smaller chromosomes. Variation in the karyotypes of A. nymphaeifolium and A. ochranthum suggested chromosomal rearrangement in the genus. All taxa showed 15 pairs of chromosomes at prometaphase I of meiosis in pollen mother cells. Four large chromosomes appeared as ring bivalents, and the rest of the chromosomes appeared as either ring or rod bivalents. Regular bivalent formation at prometaphase I of meiosis in pollen mother cells of species hybrids suggested close genomic relationships among parental taxa. On the other hand, reduction of pollen fertility estimated by pollen stainability in those hybrids suggested genetic divergence of species.     

The karyotype ofFestucopsis serpentini (Poaceae Triticeae) from Albania studied by banding techniques and in situ hybridization

The karyotypes of two populations ofFestucopsis serpentini (2n = 2x = 14) endemic to Albania were investigated in detail by Giemsa C- and N-banding, AgNO₃ staining, and in situ hybridization with an rDNA probe. The complements consisted of 14 large chromosomes, 10 metacentric and 4 SAT-chromosomes, a metacentric and a submetacentric pair. SAT-chromosomes from one population carried exclusively minute satellites, whereas SAT-chromosomes from another population also carried larger polymorphic satellites, suggesting a geographical differentiation. The existence of four chromosomes with nucleolus forming activity was established through AgNO₃ staining; however, the rDNA probe additionally hybridized to intercalary positions in the short arms of two metacentric chromosomes revealing two inactive rDNA sites. C-banding patterns comprised from zero and up to four very small to larger, generally telomeric bands per chromosome giving low levels of constitutive heterochromatin. Similarities in chromosome morphology and C-banding patterns identified the homologous relationships of all chromosomes in one population, but of three pairs only in the other. Reliable identification of homologous chromosomes between plants was only possible for the SAT-chromosomes. A comparison between the C-banded karyotypes ofF. serpentini andPeridictyon sanctum supports their position in two genera.     

Karyology and phylogeny of some Mesoamerican species of Zamia (Zamiaceae)

Chromosome numbers and karyotypes of four species of Zamia L. (Zamiaceae) are described. Plants of Z. manicata from Colombia are 2n = 18 with eight metacentric (M), four submetacentric (S), two acrocentric (A), and four telocentric (T) chromosomes. Plants of Z. ipetiensis from Panama are 2n = 23 with 3M + 4S + 2A + 14T. Plants of Z. cunaria from Panama have two different chromosome numbers, 2n = 23 with 3M + 4S + 2A + 14T and 2n = 24 with 2M + 4S + 2A + 16T. Plants of Z. acuminata from Costa Rica and Panama are 2n = 24 with 2M + 4S + 2A + 16T. On the basis of the occurrence of a one-to-two-ratio in the variation of M- and T-chromosome numbers in the karyotypes, centric fission or fusion are considered for their potential involvement in the chromosome variation of these plants. Data deriving from morphology and karyology, interpreted in a cladistic framework, suggest that centric fission rather than centric fusion is involved in the karyotype diversification of the four species and their closest Mesoamerican allies.     

KARYOTYPES OF IRIS SPECIES INDIGENOUS TO THE USSR

Randolph , L. F., and Jyotirmay Mitra . (Cornell U., Ithaca, N. Y.) Karyotypes of Iris species indigenous to the USSR. Amer. Jour. Bot. 48(10): 862–870. Illus. 1961.—The present center of diversity of the more than 200 species of Iris is in the eastern Mediterranean area of the Balkans and western Asia, with extensions of several important sections of the genus northeastward into the USSR. Karyotype analyses by the authors, previously limited chiefly to European, western Asian and American species, in this study included 10 tall bearded, dwarf bearded, regelia and oncocyclus species obtained from the USSR. A higher number of metacentric chromosomes was found in I. albertii than in any Iris species studied previously, suggesting a primitive status for this species, according to the Lewitsky concept of karyotype evolution. The 24-chromosome dwarfs, I. timofejewii and scariosa, also have more metacentric chromosomes than do Balkan dwarf species with the same chromosome number. Pumila dwarfs of the USSR have either 30, 31, or 32 chromosomes, and evidence of the mechanism concerned in this variation in number was obtained. A rare case of somatic translocation involving non-homologous acrocentric chromosomes was observed, and its significance as a source of chromosomal mutants was considered. The regelia species, I. longiscapa, rarely seen in cultivation, was found to have 18 chromosomes, which is a new number for a regelia species. The oncocyclus species, I. elegantissima and paradoxa, have karyotypes similar to those of other oncocyclus species studied previously. The potential value of Russian species of Iris in the production of more winter-hardy and otherwise desirable new kinds of garden hybrids is discussed.     

Karyotypic analysis of the gobiid fish genus Quietula Jordan and Evermann

The karyotypes of the two species of the gobiid fish genus Quietula, Q. y-cauda (Jenkins & Evermann) and Q. guaymasiae (Jenkins & Evermann), are reported for the first time. The karyotypes contained equal numbers of chromosomes (2 n =42) but differed in chromosome morphology. Quietula y-cauda has 42 acrocentric chromosomes. Quietula guaymasiae has six metacentric, four submetacentric, and 32 acrocentric chromosomes. It is suggested the karyotype of Q. guaymasiae might have been derived from that of Q. y-cauda. In addition, from comparison of the species' karyotypes of the genera Quietula and Gillichthys , it is possible the karyotype of Q. y-cauda might have been derived from that of Gillichthys mirabilis.     

KARYOTYPIC VARIATION OF EASTERN NORTH AMERICAN CLAYTONIA CHEMICAL RACES

Considerable karyotypic differentiation has occurred within the group of taxa comprising the eastern North American members of the genus Claytonia. Patterns of karyotypic differentiation are congruent with evolutionary groupings based on flavonoid chemistry, particularly at the diploid level. The 2n = 16 diploid chemotype found in both C. caroliniana and C. virginica possesses a karyotype composed entirely of metacentric chromosomes, while acrocentric chromosomes predominate in the karyotypes of the 2n = 12 and 2n = 14 diploid chemotypes of C. virginica. The 2n = 16 diploid also has a karyotype significantly larger than those of the other diploid cytotypes. Polyploid karyotypes of both species show varying degrees of divergence from their presumed diploid progenitors.