F. Douglas Wilson

Revision of Sitanion (Triticeae, Grameneae)

The species and varieties of Sitanion are caespitose perennials of rather wide distribution in western North America, the total range extending from the Pacific Coast to the 90th meridian, and from British Columbia and Alberta to Baja California and Mexico proper as far south as Hidalgo. They exhibit a wide range of adaptability to environmental conditions. Races may be found growing in such diverse habitats as the arid deserts of the Great Basin or the Columbia Basin, where average annual precipitation is from five to ten inches, or in the Arctic-Alpine meadows of the Olympic Mountains, where precipitation may be 100 inches. Members of the genus occur at elevations ranging from sea level along the Pacific Coast to above 3500 meters in some mountain ranges. Species of other genera in the Triticeae (Hordae), particularly Agropyron and Elymus, are of value as forage species in western North America. Although species of Sitanion are generally of secondary importance as forage grasses, 2 and are generally regarded as troublesome weeds, they possess certain qualities which may prove of value in research programs aimed at the development of superior range plants. Some of these are as follows:

The genome biogeography of Hibiscus L. section Furcaria DC

SummaryHibiscus L. section Furcaria DC. (Malvaceae) is a natural group of more than 100 known species, many of which are handsome ornamentals with large, showy, delicate flowers. This group includes the fiber, food, and medicinal plants kenaf, H. cannabinus L., and roselle, H. sabdariffa L. The basic chromosome number is x = 18. In nature are found diploid, tetraploid, hexaploid, octoploid, and decaploid taxa. This group displays a remarkable amount of genome diversity, as shown by cytological analysis of 140 hybrid combinations from over 60,000 crosses. At least 13 genomes are present: A, B, C, D, E, G, H, J, P, R, V, X, and Y. Subsaharan Africa is the center of genome diversity; nine of the 13 genomes are represented in African taxa, and nine of the 10 confirmed diploid species occur in Africa. Five (possibly six) genomes reside in extant diploids. The G genome (or a modified G genome) is widely distributed. Found in only one diploid species in Africa, it is found also in African tetraploid and African and Indian octoploid species, in New World tetraploid and decaploid species, and in Australian hexaploid species. The G-genome apparently was widely dispersed and differentiated, followed by hybridization, subsequent chromosome doubling, and radiation. The A, B, X, and Y genomes, on the other hand, are confined mainly to Africa, with a few taxa in Asia, and apparently are the products of a later round of hybridization and allopolyploidy.

Relationships among New World species of Hibiscus section furcaria (Malvaceae)

Seventeen species ofHibiscus sectionFurcaria are native to the New World, of which 12 (one diploid, nine tetraploids, one octoploid and one decaploid) have been studied cytotaxonomically. New chromosome counts (2n=4x=72) are reported forH. cucurbitaceus, H. flagelliformis, H. kitaibelifolius, andH. laxiflorus. Seventeen types of tetraploid interspecific hybrids (seven new to this study) all showed complete meiotic chromosome homology (genome formulaGGPP) and normal floral development. That all hybrids were nevertheless almost completely sterile suggests a cytoplasmic component to the genetic differentiation of the species. The diversification of the tetraploid species in habits, habitats and geographical ranges is considerable, despite their similar genome constitutions. A key to 17 native and four introduced African species is presented.Hibiscus cerradoensis sp. nov. is described.

Karyotypes of tragopogon (Compositae: Lactuceae)

Karyotypes of 24 diploid (2n=12)Tragopogon species are similar with one long pair of chromosomes (A), two medium-length pairs (B and C), and three short pairs (D, E, and F). These species may be divided into three karyotypic groups: 1) seven species with a satellite on A and on D; 2) 14 species with a satellite on A only; and 3) three species with a satellite on D only. Most species within karyotype groups may be separated from each other either by distinctive features of certain chromosomes or by statistical differences in length of chromosome arms or long arm: short arm ratios of chromosome A. Three tetraploid (2n=24) species had two long pairs (A,A′), four medium-length pairs (B,B′;C,C′), and six short pairs (D,D′;E,E′;F,F′). Suggestions are made as to the putative diploid parents of these presumed allotetraploids.Karyotypes of 24 diploid (2n=12)Tragopogon species are similar with one long pair of chromosomes (A), two medium-length pairs (B and C), and three short pairs (D, E, and F). These species may be divided into three karyotypic groups: 1) seven species with a satellite on A and on D; 2) 14 species with a satellite on A only; and 3) three species with a satellite on D only. Most species within karyotype groups may be separated from each other either by distinctive features of certain chromosomes or by statistical differences in length of chromosome arms or long arm: short arm ratios of chromosome A. Three tetraploid (2n=24) species had two long pairs (A,A′), four medium-length pairs (B,B′;C,C′), and six short pairs (D,D′;E,E′;F,F′). Suggestions are made as to the putative diploid parents of these presumed allotetraploids.

A cytological basis for the separation of Geropogon from Tragopogon (Compositae: Lactuceae)

The single species ofGeropogon, G. hybridus (L.) Schultz-Bip., is sometimes submerged in the morphologically similarTragopogon. A comparative study of the karyotypes ofGeropogon andTragopogon sensu stricto clarified their relationship. The karyotype ofG. hydridus (2n=14) was compared with that ofT. dubius Scop. (2n=12). The karyotypes are distinct, offering a compelling reason to recognizeGeropogon as a separate genus.

Hibiscus section Furcaria (Malvaceae) in islands of the Pacific Basin

Hibiscus sectionFurcaria includes more than 60 known taxa. The section has a mainly tropical distribution, but a few species penetrate subtropical and temperate regions. Seven taxa are recognized that occur in the islands of the Pacific Basin, five of which are endemic.Hibiscus fijiensis is described and a new combination,Hibiscus brackenridgei subsp.molokaianus, is proposed.Hibiscus sectionFurcaria includes more than 60 known taxa. The section has a mainly tropical distribution, but a few species penetrate subtropical and temperate regions. Seven taxa are recognized that occur in the islands of the Pacific Basin, five of which are endemic.Hibiscus fijiensis is described and a new combination,Hibiscus brackenridgei subsp.molokaianus, is proposed.

Clarification of the status of Hibiscus (sect. Furcaria) uncinellus (Malvaceae)

Hibiscus uncinellus andH. bifurcatus have been confused in the literature and in the herbarium. The morphological, ecological, and geographic differences between them are presented, and a lectotype is chosen for the former species.Hibiscus uncinellus is virtually confined to Mexico (plus one Guatemalan station), andH. bifurcatus occurs in the West Indies, South America, and Central America, as far north as Honduras.

The taxonomic status of hibiscus (sect. Furcaria) berberidifolius A. Rich. (Malvaceae)

This paper provides a description and a distribution map for the diploid (2n=36)H. berberidifolius A. Rich. (of sect.Furcaria), endemic to the mountain ranges associated with the Rift Valley of East Africa. It also compares salient morphological features of this species with those of the allo-octoploid (n=72) H. diversifolius Jacq., to which it has sometimes been subordinated as var.witteanus Hochr.