Life Sciences Commons^™

Complex Motor Dynamics And Control In Multi-Looped Negative Feedback Systems, Anne Beuter, John Milton, Christiane Labrie, Leon Glass

WM Keck Science Faculty Papers

Experiments were performed in normal and Parkinsonian subjects who were asked to maintain a constant finger position using time-delayed visual feedback. The finger position showed complex dynamics, with characteristic differences between normal and Parkinosonian subjects. Here we discuss some of the theoretical issues that must be resolved in order to understand the mechanisms that underlie the generation of these complex signals.

Wood Anatomy Of Cercidium (Fabaceae), With Emphasis On Vessel Wall Sculpture, Sherwin Carlquist

Aliso: A Journal of Systematic and Floristic Botany

Quantitative and qualitative data are presented for wood anatomy of the seven species of Cercidium (including two subspecies of C. floridum as well as the hybrid C. x sonorae) currently recognized. Data on wood of Parkinsonia are presented for purposes of comparison. Vessel walls of Cercidium show unusual sculpture: coarse excrescences termed verrucae here, crateriform pits, and grooves interconnecting pit apertures. These plus crystal distribution, presence of septa in fibers, pit diameter, presence of vasicentric tracheids, and presence of diagonal vessel aggregations are probably species distinctions to various degrees. The crystal-bearing fibers of Cercidium, some of which have …

Wood Anatomy Of Tasmannia, Sherwin Carlquist

Aliso: A Journal of Systematic and Floristic Botany

Quantitative and qualitative data are presented for 11 collections of eight taxa. Diameter and length of tracheids are related to plant size, but populations in cooler locations have narrower and shorter tracheids than one would expect on the basis of plant size and age, and smaller tracheids are believed to be of selective value in these environments because of their resistance to embolisms. Vesturing is absent from tracheids in taxa from warmer localities but pronounced in colder places; this, too, is a probable mechanism for resistance to embolism formation. Helical thickenings are reported for one collection of T. insipida; …

Assessing The Utility Of Isozyme Number For Determining Ploidal Level, Loren H. Rieseberg, Douglas E. Soltis

Aliso: A Journal of Systematic and Floristic Botany

In order to evaluate the utility of isozyme number for estimating ploidal level in ancient polyploid (paleopolyploid) plant species, isozyme number was determined for species of the putatively paleopolyploid genus Helianthus with n = 17, and compared with those of a species of Heliomeris with n = 8. Electrophoretic examination of 13 enzymes revealed the presence of nine duplicated isozymes in Helianthus annuus and Helianthus bolanderi and six duplicated isozymes in Heliomeris multiflora. Thus, there is little difference in isozyme number between ploidal levels. It is suggested that the lack of strong concordance between isozyme number and ploidal level …

Distribution Of Vessel Diameter In Ring-Porous Trees, D. W. Woodcock

Aliso: A Journal of Systematic and Floristic Botany

The wood anatomy of ring-porous trees presents difficulties of description and measurement. Information regarding the distribution of vessel diameters within the yearly growth increment may be of use of interpreting wood anatomy and function. Two distributional patterns can be recognized in the trunk xylem of the five ring-porous species investigated. The following terms are proposed: graduated-unimodal, to refer to ring-porous woods with one population of vessels, and graduated-bimodal, to refer to woods with two distinct peaks in vessel frequency.

Factors Limiting Sexual Reproduction In Platanus Wrightii In Southeastern Arizona, Jane H. Bock, Carl E. Bock

Aliso: A Journal of Systematic and Floristic Botany

Arizona sycamore (Platanus wrightii: Platanaceae) is a riparian tree of the southwestern United States and adjacent Mexico. It is failing to reproduce in certain canyons where mature, seed-producing trees of this species occur. Three hypotheses were tested to explain this reproductive failure: I) the presence of domestic cattle prevents reproduction, 2) seeds produced in certain canyons are inviable, and 3) annual flash floods destroy seedlings and young saplings but not the large, mature trees.

Canyons, either grazed or ungrazed by domestic animals, were surveyed for the presence of seedlings and young trees. In the laboratory, seeds were tested …

Leaf Anatomy Of The Goetzeaceae, Scott Zona

Aliso: A Journal of Systematic and Floristic Botany

A comparative study of the leaf anatomy ofthree species of three genera of Goetzeaceae (Henoonia, Goetzea, and Espadaea) revealed a number of characteristics common to all genera, viz. anomocytic stomata, sinuous anticlinal epidermal walls, both glandular and uniseriate nonglandular trichomes, crystal sand and druses in the mesophyll (often in the same cell), and intraxylary phloem. The mid veins of these species exhibit secondary growth and parenchymatous rays. The unifying anatomical features of this family are, however, not uncommon in the Solanaceae. The results of this study support placement of the Goetzeaceae in or very near Solanaceae. …

Follar Flavonoids Of Keckiella Ternata, Ron Scogin

Aliso: A Journal of Systematic and Floristic Botany

The major foliar phenolics of Keckiella ternata are quercetin 3-O-glucoside, kaempferol 3-O-glucoside, and acteoside (= orobanchin). The occurrence of flavonols in K. ternata is anomalous compared with other species of Keckiella and Penstemon, in which leaf flavonoids are based on luteolin and 6-hydroxyluteolin. The occurrence of foliar flavonols in K. ternata is interpreted as an advanced, derived condition.

Systematics Of Nama (Hydrophyllaceae), John D. Bacon

Aliso: A Journal of Systematic and Floristic Botany

Lemmonia has been maintained as a monotypic genus, despite the fact that it is morphologically very similar to several species of Nama. The major basis for this separation resides in the reportedly coalescent filament bases of Lemmonia as contrasted with the distinct filaments of Nama. Examination of corollas of Lemmonia with the scanning electron microscope has revealed that the filaments of the taxon are distinct. There is, then, no qualitative basis upon which to found Lemmonia, and the taxon is transferred to Nama.

Wood Anatomy And Relationships Of Montinia, Sherwin Carlquist

Aliso: A Journal of Systematic and Floristic Botany

Quantitative and qualitative data are presented on wood anatomy of root, basal stem, and upper stem of Montinia caryophyllacea. Anatomy of twig wood of Kaliphora madagascariensis is compared with these results, as is the data of Ramamonjiarisoa (1980) on wood of the genus Grevea. Features common to the three genera in wood as well as other portions of the plant are reviewed; these are consistent with the interpretation that Montinia and Kaliphora are very close to each other, despite previous positions of the two genera in Saxifragaceae and Comaceae, respectively. Grevea, although more distant from Montinia than …

Photosynthesis Of Arid And Subtropical Succulent Plants, Irwin P. Ting

Aliso: A Journal of Systematic and Floristic Botany

The hypothesis of Crassulacean acid metabolism (CAM) is that it is a physiological adaptation to arid or otherwise dry habitats. Stomata are closed during the day and open at night when the evaporative demand is low. Thus exogenous CO₂ is fixed at night with relatively little water loss. CAM is typically found in succulents occurring in desert and dry Mediterranean regions, but not in the cold deserts of Asia. Recently, it has become known that many arid tropical succulent plants are CAM as well, particularly those growing epiphytically. The vegetation of St. John, U.S. Virgin Islands, ranges from desertlike …

The Prey Of Common Barn Owls (Tyto Alba) In Dry Limestone Scrub Forest Of Southern Jamaica, Donald A. Mcfarlane, Kimball L. Garrett

WM Keck Science Faculty Papers

A collection of common barn-owl (Tyto alba Scopoli) pellets from caves on the Portland Ridge of Jamaica reveals that whereas introduced rodents constitute approximately 90% of the total prey, bats and birds are also frequent prey items. Of the bats, frugivorous species predominate with Ariteus flavescens Gray and Artibeus jamaicensis Leach accounting for the largest portion of the bat prey. Insectivorous bats are markedly under-represented with respect to the known diversity of insectivorous species in the habitat.

Patterns Of Species Co-Occurrence In The Antillean Bat Fauna, Donald A. Mcfarlane

WM Keck Science Faculty Papers

The bat fauna of 25 Antillean islands is presented as a species presence-absence matrix, and used to construct a large population of randomized null-model matrices by Monte-Carlo simulation techniques. Comparison of the observed data matrix with the randomized population reveals a statistically significant departure from randomness which is interpreted as evidence of community structure. The Antillean bat fauna is marked by a pattern of high species co-occurrence, with endemics dominating in the northern Antilles and undifferentiated South American taxa dominating in the southern Antilles. The 'checkerboard' distributions which have been identified in the bird populations of some tropical archipelagos are …

Taxonomy And Natural History Of Hydnora (Hydnoraceae), Lytton J. Musselman, Johann H. Visser

Aliso: A Journal of Systematic and Floristic Botany

Hydnora is a genus of subterranean holoparasitic herbs found in arid and semiarid regions of Africa, Madagascar, and the southwestern part of the Arabian peninsula. Results from field and herbarium studies suggest the genus consists of four or five species, although more than 12 have been described. The recent rediscovery of H. triceps, a plant that had remained uncollected for a century, supports the need for additional field work. Taxonomic research has been impeded by a paucity of collections, which are often fragmentary in nature and poorly preserved. Supraspecific classification, species complexes, floral biology, and uses are discussed.

Taxonomy And Morphology Of Aporomyces (Laboulbeniales), Richard K. Benjamin

Aliso: A Journal of Systematic and Floristic Botany

Thaxter's original circumscription of Aporomyces (Laboulbeniales) is emended in this study of the eight known species of the genus, three of them new: A. byrrhini, A. lutrochi, and A. physemi. The new species, as well as A. subulatus, A. szaboi, A. trinitatis, and A. uniflagellatus (type), are dioecious and occur on beetles belonging to the Limnichidae (Coleoptera: Dryopoidea). The eighth species, A. perpusillus, appears to be monoecious and occurs on Staphylinidae (Coleoptera: Staphylinoidea). All taxa are described and illustrated with line drawings and/or photographs. Aspects of thalloid structure and development are summarized. Aporomyces …

Allozyme Variation In Hellianthus Praecox Ssp. Hirtus, A Rare Sunflower From Southern Texas, Loren H. Reiseberg, Michael F. Doyle

Aliso: A Journal of Systematic and Floristic Botany

Allozyme data were used to evaluate the genetic status of a rare endemic sunflower from Texas, Helianthus praecox ssp. hirtus. Comprising approximately 200 plants, the taxon is presently known from a single population in the Carrizo Springs region of Southern Texas. Electrophoretic examination of 17 enzyme loci revealed that ssp. hirtus is genetically similar to, but distinct from, the two more widespread subspecies of H. praecox: ssp. praecox and ssp. runyonii. Levels of genetic variation in the single population of ssp. hirtus (P = 0.4 7, A = 1.88, and H = 0.17) are similar to those …