Mario A. Blanco

Phylogenetic utility of ycf1 in orchids: a plastid gene more variable than matK

Plastid DNA sequences have been widely used by systematists for reconstructing plant phylogenies. The utility of any DNA region for phylogenetic analysis is determined by ease of amplification and sequencing, confidence of assessment in phylogenetic character alignment, and by variability across broad taxon sampling. Often, a compromise must be made between using relatively highly conserved coding regions or highly variable introns and intergenic spacers. Analyses of a combination of these types of DNA regions yield phylogenetic structure at various levels of a tree (i.e., along the spine and at the tips of the branches). Here, we demonstrate the phylogenetic utility of a heretofore unused portion of a plastid protein-coding gene, hypothetical chloroplast open reading frame 1 (ycf1), in orchids. All portions of ycf1 examined are highly variable, yet alignable across Orchidaceae, and are phylogenetically informative at the level of species. In Orchidaceae, ycf1 is more variable than matK both in total number of parsimony informative characters and in percent variability. The nrITS region is more variable than ycf1, but is more difficult to align. Although we only demonstrate the phylogenetic utility of ycf1 in orchids, it is likely to be similarly useful among other plant taxa.

Floral elaiophores in Lockhartia Hook. (Orchidaceae: Oncidiinae): their distribution, diversity and anatomy.

BACKGROUND AND AIMS A significant proportion of orchid species assigned to subtribe Oncidiinae produce floral oil as a food reward that attracts specialized bee pollinators. This oil is produced either by glabrous glands (epithelial elaiophores) or by tufts of secretory hairs (trichomal elaiophores). Although the structure of epithelial elaiophores in the Oncidiinae has been well documented, trichomal elaiophores are less common and have not received as much attention. Only trichomal elaiophores occur in the genus Lockhartia, and their distribution and structure are surveyed here for the first time. METHODS Flowers of 16 species of Lockhartia were studied. The location of floral elaiophores was determined histochemically and their anatomical organization and mode of oil secretion was investigated by means of light microscopy, scanning electron microscopy and transmission electron microscopy. KEY RESULTS AND CONCLUSIONS All species of Lockhartia investigated have trichomal elaiophores on the adaxial surface of the labellum. Histochemical tests revealed the presence of lipoidal substances within the labellar trichomes. However, the degree of oil production and the distribution of trichomes differed between the three major groups of species found within the genus. All trichomes were unicellular and, in some species, of two distinct sizes, the larger being either capitate or apically branched. The trichomal cuticle was lamellate, and often appeared distended due to the subcuticular accumulation of oil. The labellar trichomes of the three species examined using transmission electron microscopy contained dense, intensely staining cytoplasm with apically located vacuoles. Oil-laden secretory vesicles fused with the plasmalemma and discharged their contents. Oil eventually accumulated between the cell wall and cuticle of the trichome and contained electron-transparent profiles or droplets. This condition is considered unique to Lockhartia among those species of elaiophore-bearing Oncidiinae studied to date.

Further Disentangling of a Taxonomic Puzzle: Maxillaria ramosa, Ornithidium pendulum, and a New Species, O. elianae (Orchidaceae)

ABSTRACT McIllmurray and Oakeley (2004) demonstrated that the name Maxillaria ramosa has been misapplied to Ornithidium pendulum since 1967, and possibly corresponds to M. cassapensis. We refer Ornithidium ochraceum, O. loefgrenii, and Maxillaria spathulata to the synonymy of O. pendulum (in addition to the already recognized synonyms O. dichotomum and Scaphyglottis tafallae), and designate a lectotype for O. dichotomum. Anew species from Venezuela and the Guianas (Ornithidium elianae), previously confused with O. pendulum, is described. An updated description of O. pendulum is presented along with a review of its complicated taxonomic history and the first record of this species for Costa Rica.

Gelatinous fibers and variant secondary growth related to stem undulation and contraction in a monkey ladder vine, Bauhinia glabra (Fabaceae)

PREMISE OF THE STUDY Some of the most striking stem shapes occur in species of Bauhinia (Fabaceae) known as monkey ladder vines. Their mature stems are flattened and develop regular undulations. Although stems have variant (anomalous) secondary growth, the mechanism causing the undulations is unknown. METHODS We measured stem segments over time (20 mo), described stem development using light microscopy, and correlated the changes in stem shape with anatomy. KEY RESULTS Growing stems are initially straight and bear tendrils on short axillary branches. The inner secondary xylem has narrow vessels and lignified fibers. As stems age, they become flattened and increasingly undulated with the production of two lobes of outer secondary xylem (OX) with wide vessels and only gelatinous fibers (G-fibers). Similar G-fibers are present in the secondary phloem and the cortical sclerified layer. In transverse sections, the concave side of each undulation has a greater area and quantity of G-fibers than the opposite convex side. Some older stems are not undulated and have less lobing of OX. Undulation causes a shortening of the stem segments: up to 28% of the original length. CONCLUSIONS Uneven distribution of G-fibers produces tensions that are involved in the protracted development of undulations. While young extending shoots attach by lateral branch tendrils, older stems may maintain their position in the canopy using undulations and persistent branch bases as gripping devices. Flattened and undulated stems with G-fibers produce flexible woody stems.

First report of naturalization of Houttuynia cordata Thunb. 1783 (Piperales: Saururaceae) in South America

A relatively large and established population of Houttuynia cordata from Itatiaia National Park in Brazil represents the first record of naturalized Saururaceae in South America. Although the species is potentially invasive, unknown mechanisms have prevented its spread to other localities between 1940, when it was recorded in cultivation in Brazil, and the present. The nearest known naturalized population is situated 5,600 km away, in Costa Rica, Central America.

On the types of Maxillaria grandiflora and Heterotaxis valenzuelana (Orchidaceae: Maxillariinae)

SummaryThe type specimen of Maxillaria grandiflora (Kunth) Lindl. was collected by Alexander von Humboldt and Aimé Bonpland during their scientific expedition to Tropical America. Its type locality, which has been the subject of confusion, is identified as a place on the eastern part of La Cruz municipality in the province of Nariño, Colombia. The type of M. grandiflora is shown to be a mixed collection and a lectotype is designated; the protologue illustration represents an amalgamation of both species. The type of Heterotaxis valenzuelana (A. Rich.) Ojeda & Carnevali was collected by José María Valenzuela but has been erroneously cited as Wright 3314 in the recent literature.