Chromosome numbers in callirhoe (Malvaceae)

Forty-four chromosome counts from the North American genusCallirhoe are reported, including first-recorded counts ofC. alcaeoides, C. digitata, C. bushii, C. triangulata, andC. involucrata var.tenuissima. Information concerning chromosome numbers from present and previous reports is summarized and evaluated. Observations are presented on meiosis for the genus in general, for male sterile individuals of gynodioecious species, and for selected F₁ hybrids. Pollen fertility data are recorded for the latter. Chromosomally three species groups are recognized: an exinvolucellate, diploid species group withn=14; an involucellate, tetraploid and octoploid species pair,n=28 and 56; and an involucellate, diploid and tetraploid species group withn=15 and 30. Intrageneric relationships and those within the tribe Malveae subtribe Malvinae are discussed.     

New species of Pectis (Asteraceae) from the West Indies,Mexico, and South America

Four new species ofPectis are described:P. ericifolia from Barbuda,P. luckoviae from west-central Mexico,P. arida from Ecuador and Peru, andP. cajamarcana from Peru. Chromosome counts forP. ericifolia (n=48) andP. luckoviae (n=12) are presented. Relationships of the newly described taxa are discussed.     

Biosystematic study of Berlandiera (Compositae)

Berlandiera is revised to includeB. subacaulis, B. pumila, B. texana, andB. lyrata with its varietieslyrata andmacrophylla. All species may be induced to interbreed readily, producing F₁ progeny which are vigorous but with reduced fertility. Sympatric species produce natural hybrids which are proposed here asB. Xhumilis (=B. pumila XB. subacaulis) andB. Xbetonicifolia (=B. pumila XB. texana). All taxa investigated hadn = 15 chromosomes, including new counts forB. subacaulis and all six F₁ hybrids.     

Chromosome counts in Clibadium (Compositae,Heliantheae) from Latin America

New meiotic chromosome counts are reported from 86 populations from Mexico to Ecuador of 13 species ofClibadium (Compositae, Heliantheae). These, plus previous reports, yield a total of 120 counts from 20 of the approximately 39 species recognized in the genus (Arriagada, in prep.). All counts aren=16 with a few fragments or B-chromosomes observed sporadically in some populations. One population, containing what appear morphologically to be interspecific hybrids betweenC. mexiae andC. microcephalum, showed one tetravalent and fragments. Species in both historical sections (Clibadium andTrixidium, created by Candolle and maintained by Schulz) and from the five sections to be proposed in a new classification of the genus (Arriagada, in prep.) have now been counted. The uniformity of chromosome numbers withinClibadium is correlated with observed allopatric distribution of closely related taxa.     

Polyploidy in Ambrosia dumosa (Compositae: Ambrosieae)

Ambrosia dumosa (A. Gray ex Torr.) Payne is one of the most abundant shrubs of the Sonoran Desert. Allopatric and sympatric populations of this species frequently exhibit distinctive morphological features, particularly with regard to leaf-segment width, but also in blooming time and ecology. Chromosome numbers ofn = 18, 36, and 54 were frequently encountered in our preliminary investigations ofA. dumosa. Fifty-six chromosome number determinations have now accumulated for this taxon, and these additional counts confirm the existence of three major chromosome races withinA. dumosa. Diploids generally occur throughout the range of the species; hexaploids tend to be confined to the deserts of California; and tetraploids occur through most of the range of the species, with the exception of southern Baja California and Owens Valley, California. External morphology was found to be correlated with chromosome number only locally, but even in many local areas, morphological intergradation occurs between different chromosome races. It is therefore considered impractical to attempt a formal taxonomy which would recognize these chromosomal races.     

Chromosome numbers and taxonomic notes for Mexican coreopsis,sections electra and pseudoagarista (compositae: heliantheae)

Notes on morphology and chromosome numbers are given for several species of MexicanCoreopsis, most of which were poorly known prior to recent collections.Coreopsis parvifolia (sectionElectra) is a large, shrubby, octoploid (2n=112) species apparently restricted to a small area in Puebla. It andC. cuneifolia (a diploid with 2n=28) appear to be closely related but differ by a number of morphological features in addition to ploidy level. A first chromosome report forC. pringlei (sectionPseudoagarista) shows this rare species to be diploid (2n=26), a fact which is in agreement with the base number of the section, i.e.,x=13. Additional collections of the very rareC. rudis andC. mcvaughii show them to be similar yet distinct species. Chromosome determinations forC. petrophila from Nayarit and Durango agree with previous counts for Jalisco populations of the species, i.e., 2n=26. Considerable morphological variation exists within this species but no subspecific entities are recognized.     

Chromosome numbers of goldenrods,Euthamia and Solidago (Compositae: Astereae). II. Additional counts with comments on cytogeography

Chromosome number determinations were made from 407 wild or transplanted individuals and seedlings representing 65 taxa and hybrids inEuthamia andSolidago. The following are first reports:Euthamia remota, 2n=9II;Solidago leavenworthii, 2n=54;S. mollis, 2n=36;S. mollis var.angustata, 2n=36;S. rigida var.glabrata, 2n=9II;S. sempervirens var.azorica, 2n=9II; andS. sparsiflora, 2n=54. Most species have been sampled only a few times or are consistently of one cytotype. Sufficient counts have been made to indicate some general patterns of cytotype distribution in the following species complexes:S. gigantea, S. canadensis, S. flexicaulis, S. rugosa, andS. uliginosa.     

Chromosome numbers and taxonomic notes in the genus Nama (Hydrophyllaceae)

Chromosome numbers are reported for 48 collections representing 15 species and three varieties ofNama. Counts for 10 taxa are initial reports, all being diploid withn = 7. Diploid counts forN. jamaicense (n = 7), previously known only as tetraploid, are also reported. Comments on the taxonomic relationships of selected taxa are included.     

Stuessya (Asteraceae: Heliantheae), a new genus from southcentral Mexico

Stuessya, a new genus from the Pacific slopes of southcentral Mexico is described. It is comprised of three species:S. apiculata, previously assigned to the genusViguiera;S. perennans, the generotype; andS. michoacana. The latter two taxa are previously undescribed. The genus is characterized by its urceolate, sclerified (at maturity) involucre. Chromosome counts of2n = 34 are reported forS. perennans. Relationships are problematical, but are reckoned to be somewhere betweenAldama andViguiera.     

Parasites ofSpodoptera exigua,S. eridania [Lep.: Noctuidae] andHerpetogramma bipunctalis [Lep.: Pyralidae] collected fromAmaranthus hybridus in field corn

Three species of lepidopterous larvae were collected fromAmaranthus hybridus L. growing in field corn during 1975 and 1976 at Hastings, Florida.Spodoptera exigua (Hubner) was the predominant species in May.Spodoptera eridania (Cramer) was predominant in June andHerpetogramma bipunctalis (F.) in July and August. Nine native species of parasites, representing theBraconidae, Eulophidae, Ichneumonidae andTachinidae, emerged from these larvae.Meteorus autographae Muesebeck emerged from bothS. exigua andS. eridania. TheTachinidae, Winthemia rufopicta (Bigot),Eucelatori rubentis (Coquillett) andLespensia sp., emerged from mixtures ofS. exigua andS. eridania. Apanteles marginiventris (Cresson),Temelucha sp., andChelonus texanus Cresson emerged from bothS. exigua andH. bipunctalis larvae, andEuplectrus platyhypenae Howard andOphion sp. emerged fromS. eridania. All the species of parasites from the lepidopterous larvae that feed onAmaranthus hybridus are also reported as parasites ofS. frugiperda, a serious pest of corn. Therefore these larvae onA. hybridus may be a source of the parasites found attackingS. frugiperda.     

New taxa in Pectis (Compositae: Pectidinae) from Mexico and the southwestern United States

Pectis minutiflora,P. papposa var.grandis, andP. purpurea var.sonorae are described as new. A new combination,P. purpurea var.lancifolia also is included. Chromosome counts (n = 12) are reported forP. papposa var.grandis andP. purpurea var.sonorae.     

Physical localization of rRNA genes by fluorescence in situ hybridization (FISH) and analysis of spacer length variants of 45S rRNA (slvs) genes in some species of genus Sesbania

The somatic chromosome numbers 2n = 12 in S. macrantha, S. coerulescens and 2n = 24 in S. simplicuscula were determined, additionally the contradictory chromosome numbers of S. bispinosa (2n = 12, 13, 14, 24) and S. pachycarpa (2n 12, 14) were determined as 2n = 24 and 2n = 14, respectively. The number of 5S rDNA sites in chromosome pair 1 was highly conserved in all the diploid and tetraploid species studied irrespective of their geographic distribution, suggesting that all diploid and tetraploid species/cytotypes of Sesbania analyzed in the present study are in close proximity. Cytogenetic mapping of the 45S multi-gene family was also carried out using fluorescence in situ hybridization. 45S rDNA was consistently located on short or long arms of two sub-metacentric chromosome pairs except on one chromosome pair in S. macrantha and on three chromosome pairs in S. bispinosa and S. cannabina. Out of these nine species, we observed the homogenization of intergenic spacer in six species and find only one spacer length variant (slv) located on one to three chromosome loci. However, three of the species were observed to have two slvs located on two different chromosomes. The species were grouped as per their evolutionary relationship on the basis of the results of the present study.     

Chromosomes ofLauxaniidae andChamaemyiidae (Diptera)

Chromosome numbers of 28 species ofLauxaniidae range from 2n=8 to 2n=12 with one having 2n=8, three having 2n=10 and 24 having 2n=12. Total complement length averaged 58.1 μ for 71 complements measured. The species studied in detail are classified according to chromosome number and morphology. The two Chamaemyiid species studied have 2n=6 and 2n=15, the latter including several microchromosomes. The karyotypical reorganizations have clearly involved inversions and translocations and a progressive reduction of chromosome numbers.     

Chromosome numbers of Orthocarpus and related monotypic genera (Scrophulariaceae: Subtribe castillejinae)

A chromosome number ofn=12 is reported for the three monotypic genera of subtribe Castillejinae:Clevelandia beldingii, Gentrya racemosa, andOpicopephalus angustifolius. Chromosome numbers ofOrthocarpus correspond mostly with current infrageneric classification. SubgenusTriphysaria hasn=11.Orthocarpus sectionsCastillejoides andCordylanthoides, which are closely related toCastilleja (x=12) and the three monotypic genera above, haven=12 with aneuploid reductions ton=10 inO. linearilobus andn=11 inO. lacerus (a species also withn=12). Tetraploids are found in two species.O. brevistylus (n=24) andO. hispidus (n=12, 24). The polyploid.O. laciniatus (n=36, 48) of Peru is postulated to be of hybrid origin between a species ofCastilleja andOrthocarpus attenuatus. SubgenusOrthocarpus sectionOrthocarpus, which hasn=14 in all species except.O. bracteosus (n=15), stands apart both morphologically and in chromosome number from the remainder of the genus.     

Chromosome numbers in some North American species of the genus Cirsium. III. Western United States,Mexico, and Guatemala

New data are presented on chromosome numbers for 36 species, two varieties, and two hybrids ofCirsium (Compositae). These include first reports forC. rhothophilum (2n = 34),C. andrewsii (2n = 32),C. crassicaule (2n = 32),C. quercetorum (2n= 32, 112),C. pascuarense (2n= 32),C. douglasii var.canescens (2n = 30, 34),C. hydrophilum (2n = 32),C. neomexicanum (2n = 30),C. cymosum (2n = 30, 34),C. acantholepis (2n= 34),C. radians (2n = 34), C.grahami (2n = 32),C. nigriceps (2n = 36),C. andersonii (2n= 32, 64),C. anartiolepis (2n = 34), andC. subcoriaceum (2n= 34). The published data on chromosome numbers of Eurasian and AmericanCirsium are summarized. In Eurasia, speciation has taken place primarily at the diploid level but is occasionally reinforced by polyploidy. The ancestral base number of 17 has been preserved in almost all species, and there is little evidence that reduction in chromosome number has played a significant role in speciation. In America speciation has proceeded exclusively at the diploid level, but the ancestral genome of 17 chromosomes has been retained in only about half of the species examined. In the remaining species, restructuring of the genome has occurred resulting in a reduction in number from 17 to 9 in extreme cases. Polyploidy, when seen, is of no significance. It is suggested that all species with greatly reduced numbers may represent products of a single reduction series.     

A comparison of type 2 diabetes risk allele load between African Americans and European Americans

The prevalence of type 2 diabetes (T2D) is greater in populations of African descent compared to European-descent populations. Genetic risk factors may underlie the disparity in disease prevalence. Genome-wide association studies (GWAS) have identified >60 common genetic variants that contribute to T2D risk in populations of European, Asian, African and Hispanic descent. These studies have not comprehensively examined population differences in cumulative risk allele load. To investigate the relationship between risk allele load and T2D risk, 46 T2D single nucleotide polymorphisms (SNPs) in 43 loci from GWAS in European, Asian, and African-derived populations were genotyped in 1,990 African Americans (n = 963 T2D cases, n = 1,027 controls) and 1,644 European Americans (n = 719 T2D cases, n = 925 controls) ascertained and recruited using a common protocol in the southeast United States. A genetic risk score (GRS) was constructed from the cumulative risk alleles for each individual. In African American subjects, risk allele frequencies ranged from 0.024 to 0.964. Risk alleles from 26 SNPs demonstrated directional consistency with previous studies, and 3 SNPs from ADAMTS9, TCF7L2, and ZFAND6 showed nominal evidence of association (p < 0.05). African American individuals carried 38–67 (53.7 ± 4.0, mean ± SD) risk alleles. In European American subjects, risk allele frequencies ranged from 0.084 to 0.996. Risk alleles from 36 SNPs demonstrated directional consistency, and 10 SNPs from BCL11A, PSMD6, ADAMTS9, ZFAND3, ANK1, CDKN2A/B, TCF7L2, PRC1, FTO, and BCAR1 showed evidence of association (p < 0.05). European American individuals carried 38–65 (50.9 ± 4.4) risk alleles. African Americans have a significantly greater burden of 2.8 risk alleles (p = 3.97 × 10^?89) compared to European Americans. However, GRS modeling showed that cumulative risk allele load was associated with risk of T2D in European Americans, but only marginally in African Americans. This result suggests that there are ethnic-specific differences in genetic architecture underlying T2D, and that these differences complicate our understanding of how risk allele load impacts disease susceptibility.     

The subdivisions of Magnistipula Engl. (Chrysobalanaceae)

A conspectus of the subgenera and sections ofMagnistipula is provided. Of the two subgenera occurring on the African mainland, subgenusMagnistipula is divided into the sectionsMagnistipula,Animalculum andPeregrinator, whereas subgen.Pellegriniella is monotypic. A Malagasy subgenus,Tolmiella, is new; its two species,M. cerebriformis andM. tamenaka, are transferred fromHirtella.     

Revision of Jaegeria (Compositae-Heliantheae)

The genusJaegeria consists of a diploid-polyploid complex of eight species found in moist habitats from Mexico to South America. The distributions, habitats, generic affinities, and tribal placement are discussed. Chromosome numbers were determined for all species exceptJ. axillaris, which is known only from Colombia.J. glabra andJ. pedunculata are diploid (2n = 18) ;J. hirta, J. macrocephala, J. gracilis, andJ. crassa are tetraploid (2n = 36) ;J. bellidiflora is octoploid (2n = 72). One Galápagos Island endemic,J. gracilis, is quite similar to the common mainland species,J. hirta, but the other endemic,J. crassa, is quite distinct from any other species.J. bellidijlora is most similar morphologically toJ. glabra;J. macrocephala is allied toJ. pedunculata. J. axillaris is somewhat distinct from the other species.     

The diploidRorippa islandica discovered in Southern Europe

A revison of herbarium material ofRorippa, revealed the presence of the diploidRorippa islandica (Oeder exMurr.) Borb. (2n=16) in several localities in Jugoslavia (Bosnia-Hercegovina and Montenegro), and probably also in Italy (Etruria). All localities occur in altitudes above 1400 m a.s.l. and constitute an extension of the distribution area of this species to Appenine and Balkan Peninsula.