Chromosome numbers of asteranthos and the putatively related Lecythidaceae

An updated review of chromosome numbers in the Lecythidaceae is presented, which includes new counts forGustavia angustifolia andLecythis lanceolata (both withn=17) and gives identifications to species for five previously published counts based on unidentified material. The earlier conclusion that the largely Asian Planchonioideae havex=13, the African Napoleonaeoideae havex=16, and the New World Lecythidoideae havex=17 still holds. The new count ofn=21 forAsteranthos brasiliensis does not support the previous treatment ofAsteranthos, a monotypic genus of the upper Amazon drainage, as the only New World representative of the otherwise tropical west African Napoleonaeoideae. Mounting evidence favors recognition of a monotypic family, the Asteranthaceae, of yet unclear relationships.     

Evolution of Lecythidaceae with an emphasis on the circumscription of neotropical genera: information from combined ndhF and trnL-F sequence data

The Lecythidaceae comprise a pantropical family best known for the edible seeds of the Brazil nut (Bertholletia excelsa) and the cannon-ball tree (Couroupita guianensis), which is planted as a botanical curiosity in subtropical and tropical gardens. In addition, species of the family are often among the most common in neotropical forests, especially in the Amazon Basin. The Brazil nut family is diverse and abundant in the Amazon and is considered to be an indicator of undisturbed or scarcely disturbed lowland forests; thus, what is learned about its evolution, ecology, and biogeography may suggest similar patterns for other Amazonian tree families. We used combined data sets derived from the ndhF and trnL-F genes to elucidate relationships of genera in both the Old and New Worlds that have been associated with Lecythidaceae. Our molecular tree agrees with the recognition of Napoleonaeaceae and Scytopetalaceae. Within the Lecythidaceae, there is molecular support for recognizing three subfamilies: Foetidioideae, Planchonioideae, and Lecythidoideae. We then focused on genera of the Lecythidoideae and found support for recognizing Allantoma (when the actinomorphic-flowered species of Cariniana are included in it), Grias, Gustavia, Corythophora, Couratari, and Couroupita, but conclude that Cariniana, Lecythis, and Eschweilera are not monoyphyletic. Because the position of the monotypic Bertholletia excelsa in relation to the other zygomorphic-flowered genera is not resolved, we are not able to comment on its generic relationships.     

Floral organogenesis and floral evolution of the Lecythidoideae (Lecythidaceae)

The subfamily Lecythidoideae of Lecythidaceae (Brazil nut family) is a dominant group in neotropical forests, especially those of Amazonia. New World members of the family have large showy flowers that are either polysymmetric or monosymmetric. In this study, floral organogenesis of all 10 neotropical genera was examined using SEM. Our observations of floral development are put into the context of a molecular phylogeny based on sequences of the ndhF and trnL-F genes (Am. J. Bot. 94: 289-301). Floral evolution of the subfamily is explained as having undergone four different levels of complexity in regard to floral symmetry. The basal most genera, Grias and Gustavia, have polysymmetric flowers. At level two, represented only by Couroupita, monosymmetry is established through the expression of abaxial dominance and the development of an androecial hood; at this level, abaxial dominance impacts the perianth and androecium, but not the gynoecium. At the third level, monosymmetry is developed in groups of Couratari and Cariniana domestica; but, in the Allantoma/Cariniana decandra lineage, a reversal back to polysymmetric flowers, resulting from a gradual weakening of abaxial dominance, and the loss of the hood has occurred. Finally, in level four, including Bertholletia, Corythophora, Eschweilera, and Lecythis, monosymmetry is so strongly expressed that the gynoecium is also influenced by abaxial dominance. In this group, the hood is complicated in both structure and function, and the floral axis is changed from straight to slightly inclined. This study demonstrates that the development of floral abaxial dominance is the proximate cause of monosymmetry in the Lecythidoideae. We suggest that monosymmetric flowers are more efficiently pollinated, and therefore the bees and bats that pollinate the monosymmetric flowers in this group are ultimately responsible for the monosymmetry.     

Phylogenetic relationships of Lecythidaceae: a cladistic analysis using rbcL sequence and morphological data

This study examined in detail the rbcL sequence and morphological support for subfamilial relationships and monophyly of Lecythidaceae. Initially we needed to establish relationships of Lecythidaceae among other dicot families. To complete this we examined 47 rbcL sequences of 25 families along with molecular observations from several large analyses of rbcL data. All analyses strongly support the monophyly of the asterid III grouping. This analysis revealed Lecythidaceae to be paraphyletic and indicated potential outgroup relationships with Sapotaceae. Once relationships had been evaluated using molecular data we then concentrated on analyzing separate and combined morphological and molecular databases. The topology of the morphological data set was similar to the rbcL sequence and combined data sets except for the positioning of Napoleonaeoideae, Grias, Gustavia, and Oubanguia. According to the combined results, Planchonioideae, Lecythidoideae. and Foetidioideae are monophyletic, whereas the subfamily Napoleonaeoideae are paraphyletic. Nested within Napolconaeoideae, we found Asteronthos forms a strongly supported clade with Oubanguia (Scytopetalaceae). Foetidia, the only genus of Foetidioideae, is sister to Planchonioideae, and this clade is sister to Lecythidoideae. The [(Planchonioideae, Foetidioideae) Lecythidoideae are sister to Asteranthos/Oubanguia. Napoleonaeoideae are sister to the rest of Lecythidaceae.     

Another perspective on cytoevolution in Lobelioideae (Campanulaceae)

The Lobelioideae is a cosmopolitan group whose cytoevolution is discussed on a model of primitively high diploid chromosome numbers, in which x = 14 is relatively plesiomorphic and x = 21 may be even more plesiomorphic. This model is suggested from the high frequency of lobelioid genera with x = 14, the probably plesiomorphic condition of x = 17 in the sister group Campanuloideae (Campanulaceae), and the primitive x = 15 in Stylidiaceae (Campanulales). It contrasts with that for a primitive x = 7 and paleopolyploidy to higher chromosome numbers. In our analysis, the genus Lobelia shows three broad cytoevolutionary groups, which probably have phylogenetic and infrageneric taxonomic significance: (1) woody diploids with x = 21 in Chile and woody diploids with x = 14 in Africa, Asia, and Hawaii; (2) herbaceous diploids with several series of dysploid chromosome numbers n = 19, 13, 12, 11, 10, 9, 8, 7, 6, mainly in Africa and Australia; (3) widespread and speciose herbaceous taxa based on a very derived n = 7, with recent frequent euploid rises (neopolyploidy) at or below the species level in subgenus Lobelia and allied or segregate genera. Other woody and herbaceous lobeliad genera have comparable cytoevolutionary patterns. New chromosome counts for Australian Lobelia, Pratia, and Isotoma illustrate the last two cytoevolutionary groups.     

Eschweilera mexicana (Lecythidaceae): A new family for the flora of Mexico

Eschweilera mexicana, a new species of Lecythidaceae from the Uxpanapa rain forests of southeastern Veracruz and adjacent Oaxaca, represents a new family for the Mexican flora. It is a locally common canopy tree in an area considered to have served as a refuge for rain forest species during the Pleistocene. Its closest relative isE. hondurensis, a species known only by one fruiting collection.     

First report of chromosome numbers of the Carlemanniaceae (Lamiales)

The Carlemanniaceae comprises two small genera that are restricted to East Asia: the Carlemannia and Silvianthus. These genera were previously placed in the Rubiaceae or Caprifoliaceae, but are now considered a distinct family that is probably related to the Oleaceae in the Lamiales. The family is still poorly understood with respect to its morphological characteristics. Here, we present the first report of the chromosome numbers of the family using species from both genera, i.e., Carlemannia tetragona, Silvianthus bracteatus ssp. bracteatus, and S. bracteatus ssp. clerodendroides. The species were compared with the chromosome numbers of Oleaceae and associated families using a Bayesian tree that was generated from rbcL and ndhF sequence data from Genbank. C. tetragona had 2n = 30 (x = 15), whereas the two subspecies of Silvianthus had 2n = 38 (x = 19). Comparisons of chromosome numbers support the distinctness of the Carlemanniaceae, not only from the Oleaceae (x = 11, 13, 23), but also from the Tetrachondraceae (x = 10, 11), a family that is possibly related to the Carlemanniaceae and/or Oleaceae in the Lamiales. The notable difference in chromosome number between Carlemannia and Silvianthus, as well as the differences in other characteristics (pollen, seed, and fruit morphology), suggests that the family split early in its evolution.     

CHROMOSOME NUMBERS IN UMBELLIFERAE. III

Chromosome numbers are reported for 156 collections representing 100 taxa of Umbelliferae. Approximately two thirds of the collections are from Mexico, Central and South America and indicate a high percentage of polyploid species in certain genera found in this area. Chromosome numbers for plants belonging to 78 taxa are published here for the first time, previously published chromosome numbers are verified for 18 taxa and chromosome numbers differing from those previously published are reported in seven instances. No chromosome counts have been previously published for nine of the genera included here. Further aneuploidy and polyploidy were found in Eryngium, and Lomatium columbianum has been found to be a high polyploid with 2n = 14x. Every chromosome count is referable to a cited herbarium specimen.     

Chromosome numbers and generic relationships in subtribe Stephanomeriinae (Compositae: Ichorieae)

Chromosome numbers are reported from over 230 populations representing species in eight genera. First counts are reported for three species ofStephanomeria, five species ofLygodesmia, and one species ofPinaropappus. Base chromosome numbers,x = 6, 7, 8, and 9 are known in the subtribe;x = 9 is found in six of the 12 genera and presumably is the ancestral base number for the subtribe. Two phyletic lines, aMalacothrix line and aStephanomeria line are recognized on morphological grounds. A key to the 12 genera is provided.     

New chromosome counts and evidence of polyploidy in Haageocereus and related genera in tribe Trichocereeae and other tribes of Cactaceae

Chromosome numbers for a total of 54 individuals representing 13 genera and 40 species of Cactaceae, mostly in tribe Trichocereeae, are reported. Five additional taxa examined belong to subfamily Opuntioideae and other tribes of Cactoideae (Browningieae, Pachycereeae, Notocacteae, and Cereeae). Among Trichocereeae, counts for 35 taxa in eight genera are reported, with half of these (17 species) for the genus Haageocereus. These are the first chromosome numbers reported for 36 of the 40 taxa examined, as well as the first counts for the genus Haageocereus. Both diploid and polyploid counts were obtained. Twenty nine species were diploid with 2n=2x=22. Polyploid counts were obtained from the genera Espostoa, Cleistocactus, Haageocereus, and Weberbauerocereus; we detected one triploid (2n=3x=33), nine tetraploids (2n=4x=44), one hexaploid (2n=6x=66), and three octoploids (2n=8x=88). In two cases, different counts were recorded for different individuals of the same species (Espostoa lanata, with 2n=22, 44, and 66; and Weberbauerocereus rauhii, with 2n=44 and 88). These are the first reported polyploid counts for Haageocereus, Cleistocactus, and Espostoa. Our counts support the hypothesis that polyploidy and hybridization have played prominent roles in the evolution of Haageocereus, Weberbauerocereus, and other Trichocereeae.     

CHROMOSOME NUMBERS OF CAMPANULACEAE. III. REVIEW AND INTEGRATION OF DATA FOR SUBFAMILY LOBELIOIDEAE

Chromosome numbers are now known for 153 species in 21 genera of Lobelioideae (Campanulaceae); this represents almost 13% of the species and 70% of the genera in the subfamily. Numbers reported are n = 6, 7, 8, 9, 10, 11, 12, 13, 14, 19, 21, 35, 70. The subfamily as a whole has x = 7; the best documented exception is Downingia and its allies with x = 11. Only four genera show interspecific variation in chromosome number: Downingia (n = 6, 8, 9, 10, 11, 12); Lobelia (n = 6, 7, 9, 12, 13, 14, 19, 21); Pralia (n = 6, 7, 13, 14, 21, 35, 70); and Solenopsis (n = 11, 14). Intraspecific variation occurs in 13 species, with as many as four different cytotypes in one species. The herbaceous members of the subfamily as a group are quite variable, showing the entire range of chromosome numbers, including numerous dysploids, but are predominantly diploid. The woody species, by contrast, are much less variable; nearly all of the species are tetraploid, with only a few diploids and hexaploids and no dysploid numbers known. These data support the hypothesis that woodiness is apomorphic within the subfamily. A general trend of higher chromosome numbers at higher latitudes and higher elevations is evident within the subfamily. The chromosome number of Apetahia raiateensis (n = 14) is reported here for the first time, on the basis of a count made about 30 years ago by Peter Raven.     

A CYTOTAXOXOMIC SURVEY OF MELAMPODIUM (COMPOSITAE-HELIANTHEAE)

Turner , B. L.. and R. M. King . (U. Texas, Austin.) A cytotaxonomic survey of Melampodium (Compositae-Heliantheae). Amer. Jour. Bot. 49(3): 233–26. Illus. 1962.—Chromosome counts are reported for individuals from 89 populations of Melampodium representing 26 species The genus is multibasic with x = 9, 10, 11, 12, 16 and 23. Chromosome numbers on a base of x = 10 characterize the section Melampodium while basic numbers of x = 23, 16, 12, 11 and 9 occur in the section Zarabellia. Melampodium camphoratum (n = 16) differs from all other species examined in having relatively small meiotic chromosomes. Only 6 of the 23 species are polyploid or have polyploid races. Melampodium leucanthum and M. cinereum have both diploid and tetraploid populations; the latter occur without any apparent morphological or geographical correlation and are probably autoploid in origin. A survey of the basic chromosome numbers known for other genera of the subtribe Melampodinae (12 of 22 genera) is presented. and it is suggested that x = 10 is the most probable basic number of the genus and subtribe.     

Chromosome numbers in antlions (Myrmeleontidae) and owlflies (Ascalaphidae) (Insecta,Neuroptera)

A short review of main cytogenetic features of insects belonging to the sister neuropteran families Myrmeleontidae (antlions) and Ascalaphidae (owlflies) is presented, with a particular focus on their chromosome numbers and sex chromosome systems. Diploid male chromosome numbers are listed for 37 species, 21 genera from 9 subfamilies of the antlions as well as for seven species and five genera of the owlfly subfamily Ascalaphinae. The list includes data on five species whose karyotypes were studied in the present work. It is shown here that antlions and owlflies share a simple sex chromosome system XY/XX; a similar range of chromosome numbers, 2n = 14-26 and 2n = 18-22 respectively; and a peculiar distant pairing of sex chromosomes in male meiosis. Usually the karyotype is particularly stable within a genus but there are some exceptions in both families (in the genera Palpares and Libelloides respectively). The Myrmeleontidae and Ascalaphidae differ in their modal chromosome numbers. Most antlions exhibit 2n = 14 and 16, and Palparinae are the only subfamily characterized by higher numbers, 2n = 22, 24, and 26. The higher numbers, 2n = 20 and 22, are also found in owlflies. Since the Palparinae represent a basal phylogenetic lineage of the Myrmeleontidae, it is hypothesized that higher chromosome numbers are ancestral for antlions and were inherited from the common ancestor of Myrmeleontidae + Ascalaphidae. They were preserved in the Palparinae (Myrmeleontidae), but changed via chromosomal fusions toward lower numbers in other subfamilies.     

Maximum likelihood inference implies a high, not a low, ancestral haploid chromosome number in Araceae, with a critique of the bias introduced by 'x'

Background and Aims

For 84 years, botanists have relied on calculating the highest common factor for series of haploid chromosome numbers to arrive at a so-called basic number, x. This was done without consistent (reproducible) reference to species relationships and frequencies of different numbers in a clade. Likelihood models that treat polyploidy, chromosome fusion and fission as events with particular probabilities now allow reconstruction of ancestral chromosome numbers in an explicit framework. We have used a modelling approach to reconstruct chromosome number change in the large monocot family Araceae and to test earlier hypotheses about basic numbers in the family.

Methods

Using a maximum likelihood approach and chromosome counts for 26 % of the 3300 species of Araceae and representative numbers for each of the other 13 families of Alismatales, polyploidization events and single chromosome changes were inferred on a genus-level phylogenetic tree for 113 of the 117 genera of Araceae.

Key Results

The previously inferred basic numbers x = 14 and x = 7 are rejected. Instead, maximum likelihood optimization revealed an ancestral haploid chromosome number of n = 16, Bayesian inference of n = 18. Chromosome fusion (loss) is the predominant inferred event, whereas polyploidization events occurred less frequently and mainly towards the tips of the tree.

Conclusions

The bias towards low basic numbers (x) introduced by the algebraic approach to inferring chromosome number changes, prevalent among botanists, may have contributed to an unrealistic picture of ancestral chromosome numbers in many plant clades. The availability of robust quantitative methods for reconstructing ancestral chromosome numbers on molecular phylogenetic trees (with or without branch length information), with confidence statistics, makes the calculation of x an obsolete approach, at least when applied to large clades.     

CHROMOSOME NUMBERS IN THE LEGUMINOSAE II: AFRICAN SPECIES,INCLUDING PHYLETIC INTERPRETATIONS

Turner , B. L., and O. S. Fearing . (U. Texas, Austin.) Chromosome numbers in the Leguminosae. II. African species, including phyletic interpretations. Amer. Jour. Bot. 46(1) : 49-57. Illus. 1959.—Chromosome numbers for 30 African legume species have been reported. These include first reports for 28 taxa, including 12 genera (Bolusanthus, Calpurnia, Melolobium, Lessertia, Sulherlandia, Colophospermum, Guibourtia, Burkea, Julbernardia, Schotia, Piliostigma and Swartzia). The counts are discussed with respect to those previously reported for related groups, and this chromosomal information was used to construct hypothetical phyletic lines at the tribal level within the subfamilies Papilionoideae and Caesalpinioideae. A phyletic scheme for the Leguminosae (excluding the Mimosoideae) based on this evidence from chromosome studies is presented. Notable departures from previously suggested phyletic treatments include: (1) Suggestion for inclusion of genera of the Galegeae and Hedysareae with base numbers of x = 10 and 11 with the Phaseoleae and Dalbergieae. (2) Derivation of the Papilionoideae through caesalpinoid prototypes, possibly from Swartzia-like ancestors. (3) Recognition of several very old chromosomal lines stemming from the subfamily Caesalpinioideae, and the suggestion that parts of the tribes Sclerolobieae, Cynometreae, Swartzieae and Sophoreae are, perhaps, more closely related to each other and to the Papilionoideae than they are to the remaining caesalpinoid tribal lines.     

CHROMOSOME NUMBERS IN COMPOSITAE VIII: HELIANTHEAE

One hundred and ninety-three new counts are reported for the tribe Heliantheae of Compositae, mostly based on determinations of meiotic material, including first counts for the genera Adenothamnus, Chrysogonum, Enceliopsis, Guardiola, Isocarpha, Lipochaeta, Otopappus, and Oyedaea, as well as first counts for 66 species. The original counts are discussed in relation to those previously reported for the tribe, by genera and subtribe. Two-thirds of the approximately 150 genera and more than a third of the roughly 1500 species have now been examined. The incomplete knowledge of generic relationships in the tribe often make the interpretation of these chromosome numbers difficult. Three observations are documented and discussed: (1) genera with low chromosome numbers are few; (2) genera with aneuploid series are abundant; and (3) the original basic chromosome number in the tribe is probably in the range of x = 8 to x = 12.     

CHROMOSOME NUMBERS AND PHYLOGENY IN MELAMPODIUM (COMPOSITAE)

The haplord chromosome numbers of n = 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species of Melampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series of x2 = 9, 10, 11, and 12. Of these four groups of species, the x = 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base in Melampodium. A comparison of morphological and cytological data from the closely related genera, Acanthospermum and Lecocarpus, indicates that the latter are probably on a common base of x = 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.     

Basic chromosome numbers of terrestrial orchids

The chromosome numbers of forty-one Brazilian species belonging to 11 genera of preferentially terrestrial orchids (subfamilies Cypripedioideae, Spiranthoideae, Orchidoideae, and Vanilloideae) were examined. Previous records for these subfamilies were reviewed in order to identify the ancestral chromosome numbers of terrestrial orchids. The variation observed within the subfamilies Spiranthoideae (2n=28, 36, 46, 48 and 92), and Orchidoideae (2n=42, 44, ca. 48, ca. 80, 84, and ca. 168) was similar to that previously reported in the literature. In the subfamily Spiranthoideae, some species of Prescottia (subtribe Prescottiinae) and some genera of Spiranthinae showed a bimodal karyotype with one distinctively large pair of chromosomes. The analysis of chromosome numbers of the genera in subfamilies revealed the predominance of the polyploid series 7, 14, 21, 28, 42 with a dysploid variation of ±1 in each ploidy level. These results suggest that the basic chromosome number of terrestrial orchids is x₁=7 for the subfamilies Spiranthoideae and Orchidoideae, as well as other Epidendroid orchids, and that the majority of the genera are composed of palaeopolyploids.     

Structure and Composition of One Hectare of Central Amazonian Terra Firme Forest1

The trees, vines, and stranglers ≥10 cm in diameter in 1 ha of terra firme forest in Amazonas State, Brazil, were measured and identified. The plot contained 645 trees representing 201 species, 95 genera, and 34 families (basal area ca 31 m²); 16 vines representing 14 species, 13 genera, and 8 families; and 1 strangler. The dominant families of trees present were the Leguminosae (sensu latu), Lecythidaceae, Sapotaceae, Burseraceae, and Moraceae; the dominant species were Clathrotropis macrocarpa (Leguminosae), Eschweilera coriacea (Lecythidaceae), and Protium hebetatum (Burseraceae). In terms of structure, diversity, and floristic composition, this plot is reasonably typical of the terra firme forests in the central Amazon, as far as this diverse biota can be typified.