A SYSTEMATIC REVIEW OF THE SUBTRIBE LAGASCEINAE (COMPOSITAE,HELIANTHEAE)

The subtribe Lagasceinae of the tribe Heliantheae is recognized traditionally to consist of two genera: Lagascea and Coulterella. Although both taxa possess uni-flowered heads aggregated into synflorescences, they are very different in most other morphological and anatomical respects. The six species of Lagascea that were investigated cytologically are n = 17, whereas the monotypic Coulterella is n = 18 with chromosomes one-half the size of those of Lagascea. The dissimilarities suggest that the two genera should not be retained in the same subtribe, and that the subtribe Lagasceinae should be abandoned. Lagascea seems to be related most closely to genera of the subtribe Helianthinae, such as Alvordia. Coulterella, on the other hand, seems closest to Flaveria of the tribe Helenieae or Senecioneae.     

A new species and subgenus of Desmanthodium (Compositae,Helianheae) from southern Mexico

Desmanthodium congestum, a new species from Chiapas, Mexico, is described and illustrated. Its morphological features are clearly distinguishable from other species of the genus, so much so that this taxon forms a new subgenus withinDesmanthodium, subgenusMultiaggregata.     

MOLECULAR PHYLOGENETICS AND EVOLUTION OF SEXUAL DICHROMATISM AMONG POPULATIONS OF THE YARROW'S SPINY LIZARD (SCELOPORUS JARROVII)

Understanding evolution of geographic variation in sexually dimorphic traits is critical for understanding the role that sexual selection may play in speciation. We performed a phylogenetic analysis of geographic variation in sexual dichromatism in the Yarrow's spiny lizard (Sceloporus jarrovii), a taxon that exhibits remarkable diversity in male coloration among populations (e.g., black, red, green, yellow, blue, brown). An mtDNA phylogeny based on approximately 880 bp from the 12S ribosomal RNA gene and 890 bp from the ND4 gene was reconstructed for 30 populations of S. jarrovii and eight other species of the torquatus species group using maximum-likelihood and parsimony methods. The phylogeny suggests that S. jarrovii consists of at least five evolutionary species, none of which are sister taxa. Although intraspecific diversity in male coloration is less than indicated by previous taxonomy, two species formerly referred to as S. jarrovii exhibit impressive geographic variation in sexual dichromatism. In one of these species, the phylogeny shows the independent evolution of a distinctive blue color morph in different parts of the species range. This pattern suggests that sexual selection may lead to striking phenotypic divergence among conspecific populations and striking convergence. Results also demonstrate the importance of a phylogenetic perspective in studies of evolutionary processes within nominal species and the problematic nature of “polytypic” species recognized under the biological species concept.     

Nuclear ribosomal DNA and karyotypes indicate a NW African origin of South American Hypochaeris (Asteraceae, Cichorieae)

Hypochaeris has a disjunct distribution, with more than 15 species in the Mediterranean region, the Canary Islands, Europe, and Asia, and more than 40 species in South America. Previous studies have suggested that the New World taxa have evolved from ancestors similar to the central European H. maculata. Based on internal transcribed spacer (ITS) sequences and fluorescence in situ hybridization (FISH) with 5S and 18S-25S rDNA of the previously overlooked Hypochaeris angustifolia from Moyen Atlas, Morocco, we show that it is sister to the entire South American group. A biogeographic analysis supports the hypothesis of long-distance dispersal from NW Africa across the Atlantic Ocean for the origin of the South American taxa rather than migration from North America, through the Panamian land bridge, followed by subsequent extinction in North America. With the assumption of a molecular clock, the trans-Atlantic dispersal from NW Africa to South America is roughly estimated to have taken place during Pliocene or Pleistocene.     

Evidence for a type III secretion system in Aeromonas salmonicida subsp. salmonicida

Aeromonas salmonicida subsp. salmonicida, the etiological agent of furunculosis, is an important fish pathogen. We have screened this bacterium with a broad-host-range probe directed against yscV, the gene that encodes the archetype of a highly conserved family of inner membrane proteins found in every known type III secretion system. This has led to the identification of seven open reading frames that encode homologues to proteins functioning within the type III secretion systems of Yersinia species. Six of these proteins are encoded by genes comprising a virA operon. The A. salmonicida subsp. salmonicida yscV homologue, ascV, was inactivated by marker replacement mutagenesis and used to generate an isogenic ascV mutant. Comparison of the extracellular protein profiles from the ascV mutant and the wild-type strain indicates that A. salmonicida subsp. salmonicida secretes proteins via a type III secretion system. The recently identified ADP-ribosylating toxin AexT was identified as one such protein. Finally, we have compared the toxicities of the wild-type A. salmonicida subsp. salmonicida strain and the ascV mutant against RTG-2 rainbow trout gonad cells. While infection with the wild-type strain results in significant morphological changes, including cell rounding, infection with the ascV mutant has no toxic effect, indicating that the type III secretion system we have identified plays an important role in the virulence of this pathogen.     

High developmental competence of pig oocytes after meiotic inhibition with a specific M-phase promoting factor kinase inhibitor,butyrolactone I

Butyrolactone I specifically inhibits M-phase promoting factor activation and prevents the resumption of meiosis. These experiments were conducted to examine effects of butyrolactone I on pig oocytes in a serum-free maturation system. The first experiment was conducted to determine the effect of butyrolactone I (0-100 microM) on nuclear maturation. At concentrations of > or =12.5 microM, germinal vesicle breakdown was prevented in >90% of the oocytes after 24 h of culture. In the second experiment, the kinetics of in vitro maturation of butyrolactone I-treated oocytes was investigated. Oocytes were treated with 0 or 12.5 microM butyrolactone I and FSH for 20 h and then cultured with LH in the absence of butyrolactone I for another 24 h. Fewer butyrolactone I-treated oocytes reached MII stage at 36 h compared with controls (5.8% vs. 62.4%, P < 0.01). However, by 44 h, 83.4% of butyrolactone I-treated oocytes reached MII compared with 88.6% of controls. In the third experiment, butyrolactone I-treated oocytes were fertilized and cultured in vitro. No differences (P > 0.05) were found between controls and treated groups in cleavage rate, blastocyst rate, or mean number of cells per blastocyst. Effects of butyrolactone I on mitogen-activated protein kinase activation and localization of microfilaments and active mitochondria were examined by Western blot analysis and laser scanning confocal microscopy, respectively. The results suggested that although butyrolactone I reversibly inhibited germinal vesicle breakdown and mitogen-activated protein kinase activation, it did not affect mitochondrial and microfilament dynamics. Butyrolactone I is a potent inhibitor of nuclear maturation of porcine oocytes, and the inhibition is fully reversible.     

Saponaria pumila (caryophyllaceae) and the ice age in the European alps

The polymerase chain reaction (PCR)-based amplified fragment length polymorphism (AFLP) technique was applied to elucidate the glacial history of the alpine cushion plant Saponaria pumila in the European Alps. Special emphasis was given to a dense sampling of populations. Our data support a survival of S. pumila during the last ice age in at least three refugia, which are characterized by unique marker sets. Patterns of genetic diversity and divergence can be explained by survival in peripheral refugia and additional in situ survival within the ice sheet on peripheral nunataks. A nunatak survival in interior parts of the Alps needs not be postulated to explain our results. The level of genetic diversity is dramatically different between populations (Shannon's diversity index: 0.87-19.86). Some peripheral populations are characterized by a high number of rare fragments indicating long isolation, but not necessarily by a high level of genetic diversity. Parts of the present distributional area were recolonized via recent long-distance dispersal, leading to severely bottlenecked populations lacking private or rare fragments. The combination of our data with palaeogeological and palaeoclimatological evidence allows us to confine Pleistocene refugia to certain regions and to draw a detailed scenario of the glacial and postglacial history of S. pumila.     

Thromboxane synthase inhibition and perinatal pulmonary response to arachidonic acid

Arachidonic acid causes dose-dependent increases in pulmonary vascular resistance in perinatal lambs. The specific metabolites that produce this effect are not known; however, a role for thromboxanes (TX's), potent constrictors of vascular smooth muscle, has been proposed. The effects of a specific inhibitor of TX synthase, OKY-1581, were tested in newborn and ventilated fetal lambs using an in situ pump-perfused lower left lobe preparation. Pulmonary and systemic responses of newborns and ventilated fetuses to infusions of arachidonic acid were evaluated in the presence and absence of OKY-1581. Increases in pulmonary vascular resistance caused by arachidonic acid were diminished by TX synthase inhibition. The degree of systemic hypotension observed with arachidonic acid infusions was significantly greater in animals receiving OKY-1581 than in animals without the inhibitor. The effect of OKY-1581 on periods of hypoxia was also evaluated in newborn lambs. There were no significant differences in the hypoxic pressor response in lambs with and without TX synthase inhibition. These results suggest that OKY-1581 can reduce most of the pulmonary vasoconstriction produced by arachidonic acid in perinatal lambs.