Hybridization and evolution in Picradeniopsis (Compositae)

The predominantly allopatric species of the genusPicradeniopsis, P. oppositifolia andP. woodhousei, are distinct in morphological, in phenolic and terpeniod chemical, and in cytological aspects (n = 24 andn = 12, respectively). In an area of sympatry in northeastern New Mexico, interbreeding occurs frequently with the production of morphologically intermediate hybrids. Morphological and phenolic chemical data from 191 plants in 40 isolated parental populations and from 91 plants in four hybrid populations are of limited value in determining the nature of this hybridization, but meiotic configurations of 12_II and 12_I and low pollen viabilities of 1–11% in the hybrids indicate that they are all of the F₁ generation (with one possible backcross). The absence of observed introgression, and therefore the absence of gene flow between the two taxa, strengthens the case for taxonomic recognition of two species in the genus. Comparisons of the morphology, phenolic and terpenoid chemistry, and cytology of parents and F₁ hybrids suggest that the tetraploid,P. oppositifolia, has arisen by allopolyploidy from a cross betweenP. woodhousei and an unknown diploid species. An extrapolated morphological and chemical reconstruction of this putative diploid parent is advanced.     

Allozyme analysis ofLuzula sect.Luzula (Juncaceae) in Ireland: Evidence of the origin of tetraploids

Luzula campestris, L. pallidula and tetraploi plants of this section from Ireland were studied electrophoretically. A hypothesis of alloploid origin for the Irish tetraploids from a hybrid betweenL. campestris andL. pallidula, based on the morphology, and karyology of the relevant taxa, has been tested. The presumed parental taxa are divergent in several loci,L. pallidula being highly homozygous andL. campestris moderately heterozygous. The Irish tetraploid combines the alleles of the putative parents, has no unique alleles, and exhibits a high frequency of heterozygotes, inAdh-2 andGpi-1, with invariably additive patterns. The Irish tetraploid has a low genotype diversity. The allozyme data support the hypothesis of alloploid origin for the Irish tetraploid withL. campestris andL. pallidula as possible parents.     

Tetraploids inLuzula multiflora (Juncaceae) in Ireland: Karyology and meiotic behaviour

Populations ofLuzula multiflora s.l. in Ireland were examined karyologically. Plants from 14 populations were invariably tetraploid with 2n=24. Chromosomes of the tetraploid are of AL type (true tetraploidy). Meiosis of the tetraploids is of the same type as described for otherLuzula taxa in the literature. In meiosis, 12 bivalents are regularly formed. A hypothesis based on the morphological and allozyme data, that the tetraploids are of alloploid origin, is supported by the present results. Meiosis in an artificial hybrid between the presumed parental taxa,L. campestris andL. pallidula, was studied; a certain tendency towards chromosome doubling was observed. The geographical distribution of theL. multiflora cytotypes is also discussed.     

SYSTEMATICS OF TRIPSACUM SECTION FASCICULATA (GRAMINEAE)

Tripsacum section Fasciculata is characterized by staminate spikelet pairs in which one spikelet is sessile and the other is supported by a long and slender pedicel. In section Tripsacum both spikelets of a staminate pair are sessile, or one is supported by a short and stout pedicel. Section Fasciculata includes five closely allied species. Tripsacum lanceolatum Ruprecht ex Fournier (2n = 72) extends from Durango in Mexico to the Huachuca mountains of southern Arizona. It resembles T. jalapense de Wet & Brink spec. nov. (2n = 72) from Guatemala in having terminal inflorescences with 3–10 racemes, but they differ in growth habit and are genetically isolated. Terminal inflorescences of the remaining three species have 15–50 racemes. Tripsacum laxum Nash (2n = 36) from the eastern escarpment of the Central Mexican Plateau is the only species of the group with essentially glabrous basal leaf-sheaths. It resembles the more widely distributed T. maizar Hernandez & Randolph (2n = 36, 72) in respect to inflorescence morphology, but is genetically isolated from this species. The widely distributed T. pilosum Scribner & Merrill (2n = 72) was divided into var. pilosum and var. guatemalense de Wet & Brink var. nov.     

Phylogenetic analysis in some Hordeum species (Triticeae; Poaceae) based on two single-copy nuclear genes encoding acetyl-CoA carboxylase

We investigate the phylogenetic relationship, and evolutionary history of 18 diploid and polyploid Hordeum species including 22 taxa based on two single-copy nuclear ACC1 and ACC2 genes using maximum parsimony, maximum likelihood, and Bayesian inference. The results of molecular phylogenetic analysis demonstrated genetic relationships among taxa and origin of polyploids. Our phylogenetic analyses revealed a clear alloploid origin of Hordeum capense, with Eurasian Hordeum marinum subsp. gussoneanum as the Xa genome donor and diploid Asian Hordeum roshevitzii as the H genome donor. The formation of hexaploid Hordeum lechleri likely involves hybridization between tetraploid Hordeum brachyantherum subsp. brachyantherum and a diploid possessing the I genome. The Acc1 and Acc2 gene data analyses suggested that Siberian Hordeum bogdanii might have be the common ancestor of the diploid New World Hordeum species. Perennial diploid South American species, Hordeum comosum was the first-diverging group within the clade of diploid American species in the analyses.     

A biosystematic study on polyploid populations of the genusSpiraea (Rosaceae) in Korea

A total of 61 chromosome counts from 11 taxa of Korean Spiraea was made. Our counts are the first report for eight taxa;S. blumei (2n=18, 36),S. chartacea (2n=36),S. chinensis (2n=36),S. fritschiana (2n=27, 36),S. microgyna (2n=18),S. prunifolia var.simpliciflora (2n=18),S. pseudocrenata (2n=36), andS. trichocarpa (2n=18). A new chromosome number of 2n=36 (tetraploid) is reported forS. pubescence. Populations of three species includingS. blumei, S. pubescence and .V.fritschiana, show different ploidy levels; diploid and tetraploid populations are found in the former two species and triploid and tetraploid ones, in latter species. Multiplication of chromosome numbers contributes to increase in size of pollen and stomata in the three species. Populations with different ploidy levels inS. blumei occupy different regions; diploid populations in inland Korea and tetraploid ones in Ullung Island. Island tetraploid population of 5.blumei might be originated from intra-island polyploidization through the introduction of diploid from inland Korea, considering the worldwide distribution of this species. Pollen fertilities of island populations of ,S′.blumei are relatively low, and sometimes no pollen grain is produced in anther sacs; it suggests that tetraploid population of the island is gynodioecious which may serve reduction of inbreeding depression.     

Dryinid (Hym.: Dryinidae) parasitoids ofDalbulus leafhopper (Hom.: Cicadellidae) in Mexico

Little is known about the natural enemies of the leafhopperDalbulus spp. (Homoptera: Cicadellidae). Searches for its dryinid (wasps) parasitoids were made in Jalisco, Mexico. Jalisco contains the greatest number ofDalbulus species, and is considered to be near to the center of origin of this leafhopper genus and its host plants: maize, teosintes (Zea spp.) and gamagrasses (Tripsacum spp.). The dryinidGonatopus bartletti was found parasitizingD. maidis on maize and on annual teosinteZea mays spp.parviglumis. G. flavipes was found parasitizingD. elimatus on perennial teosinteZ. perennis; and a new speciesG. moyaraygozai andAnteon ciudadi parasitizingD. quinquenotatus onTripsacum pilosum andT. dactyloides. Parasitism by dryinids was found at altitudes of 680–2,000 m.Dalbulus maidis, the leafhopper species which causes the greatest losses in maize in Latin America, was found to be parasitized from 680–1,760 m. TheDalbulus species associated with annual host plants (maize andZ. mays spp.parviglumis) were parasitized by dryinids during the rainy season, while theDalbulus species associated with perennial host plants (Z. perennis andTripsacum) were parasitized by dryinids during both the rainy and dry season. The greatest diversity of dryinid parasitoids ofDalbulus spp. and the highest levels of parasitism were recorded from perennial plants, indicating that such species are reservoirs of natural enemies ofDalbulus spp.     

Arceuthobium (Viscaceae) in Mexico and Guatemala: Additions and range extensions

Three new dwarf mistletoes are described:Arceuthobium globosum subsp.grandicaule (Mexico and Guatemala),A. aureum subsp.aureum (Guatemala) andA. aureum subsp.petersonii (Chiapas, Mexico).Arceuthobium guatemalense is recorded for the first time in Mexico. Significant range extensions are recorded forA. abietisreligiosae, A. divaricatum,A. gillii subsp.nigrum, andA. rubrum. New hosts are reported for several taxa. Nineteen members of the genus are presently known from Mexico, and three (possibly four) from Guatemala. Chromosome counts are reported for the first time for 3 taxa.     

Seed proteins and systematics of Tripsacum

The genus Tripsacum (Gramineae) is distributed between the latitude 42°N and 24°S in the New World. It is divided into two sections. Section Tripsacum includes 11 species with T. dectyloides (L) L. extending across the range of the genus. Section Fasciculata includes five Meso-American species with T. lanceolatum Rupr. ex Fourn. extending into southern Arizona. The genus displays considerable diversity in seed proteins. Variation patterns are of limited use in distinguishing sections, but are species and habitat specific. Protein data are particularly useful in subspecific classification, and consistently distinguish diploid from polyploid races of T. zopilotense Hern. and Randolph and T. bravum Gray. The tetraploid ectotype of T. bravum deserves specific rank and the robust ecotype of T. dactyloides var. meridonate de Wet and Timothy deserves varietal rank.     

Systematic wood anatomy of the genus Tapirira Aublet (Anacardiaceae)— a numerical approach

A wood anatomical study of the Mexican species ofTapirira was undertaken to uncover evidence to help clarify the systematics of the genus. Three to five individuals of each of 10 populations from throughout the range of the genus in Mexico were studied. For comparative purposes, three Central and South American species were also examined. Cluster analysis showed that the genus in Mexico can be separated into two phenetic units, represented byT. mexicana, a species widely distributed in Mexico, andT. chimalapana, a species endemic to the Isthmus of Tehuantepec. Canonical discriminant and factor analyses indicate that the quantitative wood characters most useful in distinguishing these species are wall thickness of fibers and vessels, diameter of fiber lumen, and diameter and frequency of radial canals. These species also differ in presence/absence of tannins in the fibers and color and specific gravity of the wood. The South American species,Tapirira bethanniana, T. guianensis, andT. obtusa, have wood anatomy similar to that ofT. chimalapana. The differences in the wood anatomical characters betweenT. mexicana and the other taxa suggest that the infrageneric classification ofTapirira should be reevaluated. The results of this study support the utility of sampling of populations in comparative wood anatomy.     

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.     

Genome synteny and evolution of AABB allotetraploids in Hibiscus section Furcaria revealed by interspecific hybridization, ISSR and SSR markers

Two tetraploid species of Hibiscus section Furcaria, H. acetosella and H. radiatus, have an AABB genomic constitution. The diploid species, H. cannabinus (AA) and H. surattensis (BB), were hybridized to develop interspecific alloploid (AB) hybrids. The synthetic interspecific hybrid exhibited intermediate morphological characters, with expression of domestication-related traits, but exhibited higher genomic association with the B genome donor. Evolution of allopolyploids in section Furcaria was found to be associated with mutations in repetitive sequences, leading to higher variation in the tetraploid genome. Allopolyploidization was observed to be associated with both loss of repetitive sequences and appearance of new alleles. Genetic diversity analysis using ISSR and cross-species SSR markers revealed a closer association of diploid genomes and high variability of tetraploid genomes. The evolution of AABB tetraploids in this section possibly took place by hybridization of the A and B genome in geographically isolated regions.     

Two Distinct Triatoma dimidiata (Latreille, 1811) Taxa Are Found in Sympatry in Guatemala and Mexico

Approximately 10 million people are infected with Trypanosoma cruzi, the causative agent of Chagas disease, which remains the most serious parasitic disease in the Americas. Most people are infected via triatomine vectors. Transmission has been largely halted in South America in areas with predominantly domestic vectors. However, one of the main Chagas vectors in Mesoamerica, Triatoma dimidiata, poses special challenges to control due to its diversity across its large geographic range (from Mexico into northern South America), and peridomestic and sylvatic populations that repopulate houses following pesticide treatment. Recent evidence suggests T. dimidiata may be a complex of species, perhaps including cryptic species; taxonomic ambiguity which confounds control. The nuclear sequence of the internal transcribed spacer 2 (ITS2) of the ribosomal DNA and the mitochondrial cytochrome b (mt cyt b) gene were used to analyze the taxonomy of T. dimidiata from southern Mexico throughout Central America. ITS2 sequence divides T. dimidiata into four taxa. The first three are found mostly localized to specific geographic regions with some overlap: (1) southern Mexico and Guatemala (Group 2); (2) Guatemala, Honduras, El Salvador, Nicaragua, and Costa Rica (Group 1A); (3) and Panama (Group 1B). We extend ITS2 Group 1A south into Costa Rica, Group 2 into southern Guatemala and show the first information on isolates in Belize, identifying Groups 2 and 3 in that country. The fourth group (Group 3), a potential cryptic species, is dispersed across parts of Mexico, Guatemala, and Belize. We show it exists in sympatry with other groups in Peten, Guatemala, and Yucatan, Mexico. Mitochondrial cyt b data supports this putative cryptic species in sympatry with others. However, unlike the clear distinction of the remaining groups by ITS2, the remaining groups are not separated by mt cyt b. This work contributes to an understanding of the taxonomy and population subdivision of T. dimidiata, essential for designing effective control strategies.     

A revision ofTaraxacum sect.Piesis (Compositae)

On the basis of allozyme and cultivation data, and of additional herbarium material, a taxonomic and nomenclatural revision ofTaraxacum sect.Piesis A.J. Richards exKirschner et?těpánek is provided. The section is made up of halophilous, sexually reproducing taxa. InT. stenocephalum Boiss. etKotschy,T. pindicum Kirschner et?těpánek, sp. nov., andT. perenne Kirschner et?těpánek, sp. nov., a tetraploid chromosome number has been recorded, representing the only known case of sexuality at the tetraploid level in the genus. The complex ofT. stenocephalum, includes some geographically and morphologically extreme populations treated as subspecies: subsp.gumusanicum (Soest)Kirschner et?těpánek, comb. nov., subsp.magnum Kirschner et?těpánek, subsp. nov., and subsp.daralagesicum (Schischk.)Kirschner et?těpánek, comb. nov. In addition toT. bessarabicum (Hornem.)Hand.-Mazz., a widely distributed Eurasian species,T. stenocephalum, a complex centred in Transcaucasia and Anatolia, andT. pachypodum H. Lindb., a North African endemic, four new species are described:T. salsum Kirschner et?těpánek, sp. nov., a diploid endemic confined to E Crimea,T. perenne Kirschner et?těpánek, sp. nov., a tetraploid sexual species known only from SW Crimea,T. pindicum Kirschner et?těpánek, sp. nov., a remarkable tetraploid endemic to the Pindos Mts., Greece, andT. salsitatis Kirschner, ?těpänek etYirdirimli, sp. nov., an Anatolian diploid species. Furthermore, a hybrid betweenT. salsum andT. bessarabicum from Crimea (documented on the basis of allozyme data elsewhere) is given a binomial,T. xmesohalobium Kirschner et?těpánek, nothosp. nov.     

Allozyme variation in Japanese species ofChionographis (Liliaceae)

Allozyme variation was examined in three diploid taxaChionographis japonica var.japonica, var.kurokamiana, andC. koidzumiana and three tetraploid taxaC. japonica var.kurohimensis, ssp.hisauchiana, and ssp.minoensis. Results show thatC. japonica var.kurokamiana is genetically closer toC. koidzumiana than to var.japonica. In the tetraploid taxa, fixed heterozygosities were found at several loci, and this supports the hypothesis that these taxa are allotetraploids. Furthermore, the tetraploid taxa have many unique alleles not found in the diploid taxa. This suggests that sufficient time has passed since the origin of tetraploids for new mutations to have been fixed.     

The flavonoids in leaves of diploidTriticum species (Gramineae)

Leaf flavonoids have been identified in seven species ofTriticum, all of which have been considered at one time as putative parents of the cultivated tetraploid and hexaploid wheats. The major constituents are apigenin- and luteolin-based glycosylflavones, some of which contain various O-glycosidic attachments at the 6-position. Four tricin glycosides are present in minor amount, as is free tricin. The flavonoid patterns link togetherT. searsii, T. speltoides andT. squarrosa, on the one hand, andT. monococcum, T. boeoticum, T. thaoudar andT. urartu, on the other. These results indicate that the first three taxa are more likely to be diploid ancestors to the hexaploidT. aestivum than the latter four species.     

Evidence for autoploid evolution in the artemisia ludoviciana complex of the Pacific Northwest

TheArtemisia ludoviciana complex of the Northwest is considered to be an intervarietal autoploid complex on the basis of evidence obtained from cytogenetic analysis. The evidence includes the occurrence of chromosomal races within all but two of the inclusive taxa, the degree and constancy of multivalent formation in the polyploid races, and the high degree of homology among the genomes of the various taxa as demonstrated by the pairing relationships in the F₁ progeny. Both triploid and tetraploid progeny were produced in diploid-tetraploid crosses, and the tetraploid offspring were fully as fertile as the natural tetraploids. The triploids, on the other hand, produced very few viable pollen grains. The production of tetraploid offspring in interracial crosses could provide a mechanism for gene flow from the diploid to the tetraploid population. With the observation of both diploid and tetraploid populations ofA. douglasiana, in addition to the well-known hexaploid, a reasonable doubt is cast upon the putative amphidiploid origin of the hexaploid via hybridization betweenA. suksdorfii andA. ludoviciana.     

Carex hermannii (Cyperaceae), a new species from Mexico,with comments on related species at high altitudes in middle America

Carex hermannii, a new species known only from a few populations on large volcanic mountains on the Puebla-México state border, central Mexico, is described, illustrated and compared with its nearest relative,C. cuchumatanensis of Guatemala. Both these species have been confused until now with the more distantly relatedC. endlichii. Morphological comparisons ofC. hermannii, C. cuchumatanensis andC. endlichii confirm the distinctiveness of these species.     

Chromosome numbers,polyploidy, and hybridization in castilleja (scrophulariaceae ) of the Great Basin and Rocky Mountains

Chromosome numbers are reported for 190 collections ofCastilleja of the Great Basin-Rocky Mountains and adjacent regions in western North America. Polyploidy has played a major role in evolu tion of this genus. Of the 35 taxa represented, 14 are exclusively diploid (n =12). The remaining 21 taxa exhibit polyploidy: eight are tetraploid only, two are octopIoid only, while 11 of the more wide-ranging species have two or more levels of polyploidy. BothC. rhexifolia andC. sulphured have diploid, tetraploid, and octoploid races while the widespreadC. miniata has four (2x, 4x, 8x, and 10x). Where appropriate, the role of polyploidy and hybridization inCastilleja evolution and their relevance to taxonomy are discussed for individual species.