Showing papers in "Aliso in 2000"
TL;DR: Qualitative and quantitative data are presented for wood of all species of Fouquieriaceae, the samples selected so as to cover important variables with respect to organography and age, but few wood features offer species characters.
Abstract: Qualitative and quantitative data are presented for wood of all species of Fouquieriaceae, the samples selected so as to cover important variables with respect to organography and age . Wood contains fibertracheids (plus a few vasicentric tracheids) . Diffuse axial parenchyma is mostly grouped as diffusein-aggregates or diffuse clusters (new term), with transitions to pervasive axial parenchyma in some species. Rays are Heterogeneous Type II. These wood features are relatively unspecialized and are consistent with placement of the family in Ericales s.1. as defined in recent DNA-based cladograms. Xeromorphic wood in nonsucculent species occurs only in Fouquieria shrevei; the lateral branches of F. columnaris also have xeromorphic wood . If the preceding two instances and proliferated parenchyma of Lhe three succulent species (F. columnaris, F. fasciculata, and F. purpusii) are excluded from quantitative studies, wood of Fouquieriaceae is rather mesomorphic, despite Lhe habitats occupied by the family. This paradox is explained by the very sensitive drought deciduousness. Also, the succulent species produce water-storage parenchyma by means of expansion of rays and axial parenchyma bands. Details of these two types of meristems, as well as three other types of meristems within wood (not including vascular cambium) and four bark meristems (other than phellogen) are described; five of these merisrerns are newly reported for the family. Wood data permit recognition of both the three succulent and eight nonsucculent species within a single genus, in agreement with Henrickson (1972), but few wood features offer species characters. Most wood features, including the abundant reaction wood, are closely related to habit, organography. and ecology.
33 citations
TL;DR: A parsimony analysis based on sequences from the ITS region and two partitions of the 26S subunit of nuclear ribosomal DNA was used to infer phylogenetic relationships among the North American species of Phoradendron, confirming the hypothesis that species lacking cataphylls are polyphyletic.
Abstract: A parsimony analysis based on sequences from the ITS region and two partitions of the 26S subunit of nuclear ribosomal DNA was used to infer phylogenetic relationships among the North American species of Phoradendron. A strongly supported clade united all but one of the species typically lacking ca taphylls, a character used previously to distinguish the northern species from those of Central and South America. The divergent placement of P. califo rnicum rel ative to the members of this \" northern\" clade confirmed the hypothesis that species lacking cataphylls are polyphyletic. Four of five species parasitic on conifers formed a well-supported clade. However. a strongly supported relati onship between P. rhipsa/inum and P. bra chystachyum, the former a parasite of conifers, renders con ifer parasitism homoplastic . A s ister group rel ationsh ip between these two species is not appare nt from morphological evidence. A clade unit ing P. serotinum, P. tomentosum, and P. velutinum was strongly supported. A broad host range characterized two of the three lineages of the basal trit omy in the northern clade, whereas the third line age united species specialized in parasitism of oaks or conifers.
12 citations
11 citations
TL;DR: The reproductive barriers to hybridization operating within the genus Yucca are examined, i.e., spatial, temporal and ethological, and circumstances that may have been responsible for the production and widespread distribution of hybrids in the Il-C.
Abstract: Yuccas (Yucca, Agavaceae) are an easily recognizable constituent of the vegetation of the International Four Corners; an area made up of portions of Arizona, New Mexico, Sonora and Chihuahua. We recognize three species as native to the region, Yucca baccata, Y. elata and Y. madrensis, together with interspecific hybrids, and document for the first time naturally occurring intersectional hybridization between baccate-fruited (sect. Yucca) and capsular-fruited (sect. Chaenocarpa) species. We examine the reproductive barriers to hybridization operating within the genus, i.e., spatial, temporal and ethological, and we consider circumstances that may have been responsible for the production and widespread distribution of hybrids in the Il-C. These include establishment of syrnpatry, pollinator biology, founding hybrids and human activities. We also reflect on the present situation regarding sexual reproduction in species of Yucca in the Southwest.
8 citations
TL;DR: Xylem of roots and rhizomes of five species of four genera of tribe Cheilantheae of Pteridaceae has been studied by means of scanning electron microscopy, indicating that different perforation plate modifications are represented in the cheilanthoid ferns of these habitats.
Abstract: Xylem of roots and rhizomes of five species of four genera of tribe Cheilantheae (Pteridaceae; recently recognized by some as a segregate family, Cheilanthaceae) has been studied by means of scanning electron microscopy (SEM) . All of these species occur in habitats (cliffs, talus) of mountains of North America that are seasonally dry in summer and cold in winter. The vessels prove diverse , indicating that different perforation plate modifications are represented in the cheilanthoid ferns of these habitats, rather than different degrees of the same kind of modification. The modifications include wide perforations alternating with narrow perforations (especially prominent in Bommeria); discontinuous perforation plates tCheilanthes, Pella ea ); and narrow, slitlike perforations iCh eilanthes) . The discontinuous perforation plates are newly reported for ferns. The exceptionally prominent perforations of Bommeria vessels may be correlated with greater laminar surface and higher transpiration during wet periods in that genus; the other genera have small laminae with probable low transpiration rates even during moist periods.
7 citations
TL;DR: This work accepts Engelmann 's designat ion as the earliest applicable binomial but accord it a change in status as Y.schottii Engelmann pro, sp.
Abstract: George Engelmann 's con cept of Y. schottii as a plant with short, stiff, ye llo w-gree n leaves has not been accepted by recent authors who apply the name to plants of southern Arizona with broad, flexible blue-green leaves. Interspecific hybrids among three yuc ca s present in the area , Y. baccata , Y. elata, and the wide, blue -green leafed plant are co mmo n. We bel ieve that Arthur SChOll'S co llec tions made in 1853 upon which Engelmann based his de scription are of hybrid origin. We accept Engelmann 's designat ion as the earliest applicable binomial but accord it a change in status as Y. x.schottii Engelmann pro , sp. and apply it as a co llective epithet to include all hybrids among the thre e species . We designate Schott 's unnumbered gathering in the Torrey Herbarium (NY) as lectotype. We consider that Y. schottii of authors is con specific with Y. madrensis Gentry of Chihuahua and Sonora , Mexico.
4 citations
TL;DR: Five new taxa of Mexican Euphorbiaceae are described, one of which appears to be most closely akin to Croton fru tic ulosus Torr.
Abstract: This article conta ined descriptions of five new taxa of Mexican Euphorbiaceae. Euphorbia (sub g. Agaloma) na yarensis is endemic to pine-oak woodland in the mount ains of central Nayarit. It appears related to E. so ob yi but differs by possessing linear to linear-ovate leaves. Croton varelae is also endemic to central Nayarit. A key was provided to distinguish this spec ies. a member of sect. Geiseleria, from the seven other Mex ican species of this section. Croton ram illatus var. magniglandulifer occurs in the states of Guerre ro and Morelos. This new varie ty differs from var. ramillatus by the possession of larger petiolar glands . Croton michaelii occurs in Agu ascaliente s and Durango. It is uncertain to which section of Croton this species belongs. It resembl es Croton yecorensis but is distinguished by possessing a lepid ote indumentum and by lacking con spicuous s tipitate glands. Crot on disjun ctus has been coll ected in Chihuahua and Agua scalientes, at localiti es se parated by more than 600 km. Thi s species appears to be most closely akin to Croton fru tic ulosus Torr., from which it is separated by glabrous, ev ident (vs. pube scent, nearl y obso lete) stipules and multifid (vs. bifid) sty les.
3 citations
TL;DR: A major reclassification with 59 new combinations, and the application of several additional combinations not used in recent years is applied.
Abstract: Three hundred seventy nine species of Polemoniaceae are arranged in a phylogenetic classificat ion composed of three subfamilies, eight tribes. and 26 genera. Nomenclature of one tribe is clarified and the circumscription of several tribes differs greatly from previous classifications. Five new genera, Bryantiella, Dayia, Lathrocasis, Microgilia, and Saltugilia, are proposed. In addition, four new species are described from the genera Allophyllum, Dayia, Giliastrum, and lpomopsis. This treatment repr esents a major reclassification with 59 new combinations, and the application of several additional combinations not used in recent years .
TL;DR: Genera of Phytolaccaceae studied here have the same ontogenetic features leading to successive cambia as Stegnospernwl.
Abstract: Quantitative and qualitative wood features are presented and analyzed for seven species of subfamily Rivinoideae and four of subfamily Phytolaccoideae. All species have nonbordered perforations plates, as elsewhere in suborder Phylocaccineae. Libriform fibers characterize both subfamilies, but vasicentric tracheids occur in two rivinoid species. Axial parenchyma is vasicentric scanty (apotracheal bands and patches in one species). Rays are mostly multiseriate, with procumbent cells infrequent in most species. Rivinoids and phytolaccoids differ from each other in ray height and width and in crystal types. The xeromorphic wood of Petiveria and Rivina is related to their short duration (woody herbs) in disturbed soil that dries readily. Woods of other genera are moderately mesomorphic, correlating with seasonally tropic habitats. Genera of Phytolaccaceae studied here have the same ontogenetic features leading to successive cambia as Stegnospernwl. Pliytolacca dioica has amphivasal pith bundles in which secondary growth occurs. Vessel restriction patterns are newly reported for the family.
TL;DR: An inventory of the vegetat ion types of Castelporziano Estate, including examples of Mediterranean ecosystems in exce lle nt preserved condition, filled well into 14 biomass classes; the highest values were related to stratified forested vegetation types.
Abstract: An inventory of the vegetat ion types of Castelporziano Estate (Ro me) . including examples of Mediterranean ecosystems in exce lle nt preserved condition . was co mpiled . Because Leaf Area Index (LA!) changed with forest struc ture and developmental stages. maximum LA! pro vided a good estimate of maximum biomass accumulation . Plant biomass estimation. ranging from 61 tons ha ' to 360 tons ha\" , filled well into 14 biomass classes; the highest values (from 301 ton s haI to 360 tons ha\") were related to stratified forested vegetation types. including the more mature Pinus pinea plantations. Quercus ilex evergreen forests and broad leaf mixed forests . LA! ranged from 0.5 to 4 .5, and changed with fore st structure . increas ing with the increase of plant biomass. Leaf area index measurements filled well into nine LA! classes . and the highest values were related to the stratified vegeta tion types. Biomass and LA! maps might be employed as a computerised mapped information sys tem for natural resource policy. reg ional planning. and landscape man agement. Long-term monitoring may easily be achieved by LA! measurements whi ch can be convened to biomass values by the identified relationship between plant biomass and LA!.