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Articles 1 - 29 of 29
Full-Text Articles in Life Sciences
New Caribbean Locality For The Extinct Great White Shark Carcharodon, Clare Flemming, Donald A. Mcfarlane
New Caribbean Locality For The Extinct Great White Shark Carcharodon, Clare Flemming, Donald A. Mcfarlane
WM Keck Science Faculty Papers
Carcharodon is represented by a single upper tooth (Fig. 1) which we extracted from the eroding Pliocene limestone wall, some six meters above the floor at the northern end of Darby Sink. Much of the tooth is missing, but the remaining portion includes features diagnostic of this genus. The tooth conforms in size and morphology to Carcharodon megalodon (Agassiz, 1843), an extinct great white shark.
A Second Pre-Wisconsinan Locality For The Extinct Jamaican Rodent, Clidomys (Rodentia: Heptaxodontidae), Donald A. Mcfarlane, Joyce Lundberg, Clare Flemming, Ross D. E. Macphee, Stein-Erik Lauritzen
A Second Pre-Wisconsinan Locality For The Extinct Jamaican Rodent, Clidomys (Rodentia: Heptaxodontidae), Donald A. Mcfarlane, Joyce Lundberg, Clare Flemming, Ross D. E. Macphee, Stein-Erik Lauritzen
WM Keck Science Faculty Papers
Clidomys is the most distinctive but least well known member of the late Quaternary terrestrial mammal fauna of Jamaica. Here we report the second dated locality for this genus. The Illinoisan age we report further strengthens arguments we have made elsewhere, that Clidomys represents an early - probably pre-Wisconsinan - extinction that contrasts with the growing record of Holocene extinctions in the Antilles.
The Age Of The Kirkdale Cave Palaeofauna, Donald A. Mcfarlane, Derek C. Ford
The Age Of The Kirkdale Cave Palaeofauna, Donald A. Mcfarlane, Derek C. Ford
WM Keck Science Faculty Papers
The Kirkdale Cave palaeofauna represents the original and classic 'warm', interglacial mammalian cave deposit in Britain. Although long considered to be 'Ipswichian' in age, no previous attempts to obtain radiometric dates have been recorded. Here we report a uranium-series disequilibrium date of 121,000 ± 4000 yr BP on a flowstone capping that overlay the original bone bed. The precision of the date exceeds that obtained at any other British Interglacial cave site, and permits tentative correlation with the high precision ice core records now available.
Energy Absorption During Running By Leg Muscles In A Cockroach, Robert J. Full, Darrell R. Stokes, Anna N. Ahn, Robert K. Josephson
Energy Absorption During Running By Leg Muscles In A Cockroach, Robert J. Full, Darrell R. Stokes, Anna N. Ahn, Robert K. Josephson
All HMC Faculty Publications and Research
Biologists have traditionally focused on a muscle's ability to generate power. By determining muscle length, strain and activation pattern in the cockroach Blaberus discoidalis, we discovered leg extensor muscles that operate as active dampers that only absorb energy during running. Data from running animals were compared with measurements of force and power production of isolated muscles studied over a range of stimulus conditions and muscle length changes. We studied the trochanter-femoral extensor muscles 137 and 179, homologous leg muscles of the mesothoracic and metathoracic legs, respectively. Because each of these muscles is innervated by a single excitatory motor axon, …
Fission Yeast Mitotic Regulator Dsk1 Is An Sr Protein-Specific Kinase, Zhaohua Irene Tang, Mitsuhiro Yanagida, Ren-Jang Lin
Fission Yeast Mitotic Regulator Dsk1 Is An Sr Protein-Specific Kinase, Zhaohua Irene Tang, Mitsuhiro Yanagida, Ren-Jang Lin
WM Keck Science Faculty Papers
Intricate interplay may exist between pre-mRNA splicing and the cell division cycle, and fission yeast Dsk1 appears to play a role in such a connection. Previous genetic analyses have implicated Dsk1 in the regulation of chromosome segregation at the metaphase/anaphase transition. Yet, its protein sequence suggests that Dsk1 may function as a kinase specific for SR proteins, a family of pre-mRNA splicing factors containing arginine-serine repeats. Using an in vitro system with purified components, we showed that Dsk1 phosphorylated human and yeast SR proteins with high specificity. The Dsk1-phosphorylated SF2/ASF protein was recognized strongly by a monoclonal antibody (mAb104) known …
Shifting Paradigms In Island Biology, Sherwin Carlquist
Shifting Paradigms In Island Biology, Sherwin Carlquist
Aliso: A Journal of Systematic and Floristic Botany
The ease of travel by jet aircraft has opened up island areas not only for study but also for introduction of weeds, pests, and pathogens. We are at a critical juncture in the study of island organisms, which have become more accessible at the same time that they are vanishing. With the urgency for study of island organisms, we have many new tools, especially molecular ones, which have validated the existence of long-distance dispersal in unexpected ways. These tools, together with the ease of staying for longer periods on islands, have permitted us to understand many aspects of evolutionary adaptation …
Plant Conservation In The Juan Fernandez Archipelago, Chile, Tod F. Stuessy, Ulf Swenson, Daniel J. Crawford, Gregory Anderson, Mario Silva O.
Plant Conservation In The Juan Fernandez Archipelago, Chile, Tod F. Stuessy, Ulf Swenson, Daniel J. Crawford, Gregory Anderson, Mario Silva O.
Aliso: A Journal of Systematic and Floristic Botany
Oceanic archipelagos often hold very specialized floras with high degrees of endemism. These floras are frequently highly vulnerable to disturbance by natural causes and human intervention. The Juan Fernandez Islands (Chile) in the Pacific Ocean are a small archipelago of only three islands. Since discovery in 1574 by Juan Fernandez, human activities have altered floristic composition and survival circumstances of the endemic species. In this paper we document past and present means of disturbance, both anthropogenic and natural, which have influenced the native vegetation. The most destructive past activities have been logging and .introduction of animals and plants, both deliberately …
Landscape Management Challenges On The California Channel Islands, William L. Halvorson
Landscape Management Challenges On The California Channel Islands, William L. Halvorson
Aliso: A Journal of Systematic and Floristic Botany
Managing for sustained biodiversity and restoration of natural habitat has become increasingly important over the last two decades, first as mitigation for development (especially in wetlands), and , more recently in natural areas. The latter has come about as land managing agencies like the Department of Defense and Bureau of Land Management have seen the need to reverse the impact of past land uses and agencies like the National Park Service and The Nature Conservancy have taken on the responsibility for less-than-pristine lands.
On the California Channel Islands, the need for restoring and managing biodiversity is great, but this restoration …
Conserving Plants As Evolutionary Entities: Successes And Unanswered Questions From New Zealand And Elsewhere, Ian A. E. Atkinson
Conserving Plants As Evolutionary Entities: Successes And Unanswered Questions From New Zealand And Elsewhere, Ian A. E. Atkinson
Aliso: A Journal of Systematic and Floristic Botany
Saving a species from extinction may not insure that its future will continue as before, even when the surviving population is in a wild habitat. Former selection forces may be missing or replaced by others so that the species develops along a different evolutionary pathway. Such disruption of evolutionary direction may be particularly important for island taxa given that modification by humans and their introduced organisms is making many islands more similar to continental habitats. In restoring habitats for island species, special attention should therefore be given to identify ing the major selective forces likely to have been operating during …
Plant Conservation In A Changing World, Peter H. Raven
Plant Conservation In A Changing World, Peter H. Raven
Aliso: A Journal of Systematic and Floristic Botany
No abstract provided.
Wood Anatomy Of Resedaceae, Sherwin Carlquist
Wood Anatomy Of Resedaceae, Sherwin Carlquist
Aliso: A Journal of Systematic and Floristic Botany
Quantitative and qualitative data are presented for seven species of four genera of Resedaceae. Newly reported for the family are helical striations in vessels, vasicentric and marginal axial parenchyma, procumbent ray cells, and perforated ray cells. Wood features of Resedaceae may be found in one or more of the families of Capparales close to it (Brassicaceae, Capparaceae, Tovariaceae). Lack of borders on pits of imperforate tracheary elements is likely a derived character state. Wood of Reseda is more nearly juvenile than that of the other genera in ray histology; this corresponds to the herbaceousness of Reseda. The quantitative features …
Wood Anatomy Of Portulacaceae And Hectorellaceae: Ecological, Habital, And Systematic Implications, Sherwin Carlquist
Wood Anatomy Of Portulacaceae And Hectorellaceae: Ecological, Habital, And Systematic Implications, Sherwin Carlquist
Aliso: A Journal of Systematic and Floristic Botany
Qualitative and quantitative wood data are given for 13 species of 10 genera of Portulacaceae (secondary xylem from additional species of Anacampseros and Lewisia were studied but not quantitatively analyzed). Most Portulacaceae show modifications that can be related to the succulent habit, including wide, tall rays mostly composed of thin-walled cells; total or partial substitution of axial parenchyma for libriform fibers ; and modified patterns of pitting on lateral walls of vessels. Pseudoscalariform pitting is more common in Portulacaceae than in other dicotyledon families. In vessels of Anacampseros wood, wide helical bands of secondary wall materi al are present. Similar …
Laboubeniales On Semiaquatic Heteroptera. Vii. Addenda To Species Of Triceromyces On Hydrometridae And Further Observations On Dioecism In The Order, Richard K. Benjamin
Laboubeniales On Semiaquatic Heteroptera. Vii. Addenda To Species Of Triceromyces On Hydrometridae And Further Observations On Dioecism In The Order, Richard K. Benjamin
Aliso: A Journal of Systematic and Floristic Botany
Four new species of Triceromyces (Laboulbeniales) parasitic on Hydrometra (Heteroptera: Hydrometridae) were described and aspects of their morphology and development were discussed and illustrated with line drawings. Two of the species, T. floridanus and T. elongatus, are monoecious; T. floridanus, known only from Florida, U.S.A., has features allying it with T. elongatus, which ranges from Madagascar and Kenya in Africa to India, Indonesia, and Sri Lanka in Asia. The other two undoubtedly closely related species, T. lithophilus and T. terrestris, are dioecious and parasitize two closely related endemic species of Hydrometra thriving in a small region …
A Floristic Study In The Diamond Creek Drainage Area, Gila National Forest, New Mexico, Eric H. Roalson, Kelly W. Allred
A Floristic Study In The Diamond Creek Drainage Area, Gila National Forest, New Mexico, Eric H. Roalson, Kelly W. Allred
Aliso: A Journal of Systematic and Floristic Botany
The Diamond Creek drainage is one of the major watershed systems of the Gila National Forest in southwestern New Mexico. The purposes of this study were to catalog the vascular plants of a portion of this drainage area, describe the vegetation zones, locate any threatened, endangered, or sensitive plant species, and assess plant regeneration in areas that have been burned. The study area is located in the eastern portion of the Gila National Forest along the Black Range in the northwest corner of Sierra County. It covers approximately 5600 hectares (14000 acres) and ranges in elevation from 2250 to 3000 …
Wood Anatomy Of Calyceraceae With Reference To Ecology, Habit, And Systematic Relationships, Sherwin Carlquist, Melanie L. Devore
Wood Anatomy Of Calyceraceae With Reference To Ecology, Habit, And Systematic Relationships, Sherwin Carlquist, Melanie L. Devore
Aliso: A Journal of Systematic and Floristic Botany
Qualitative and quantitative data are presented for secondary xylem of 14 species of four genera of Calyceraceae; root wood is studied for acaulescent perennials and one annual. The wood anatomy of most species of Calycera has character states identical to those seen in wood of most Asteraceae (including phylads of Asteraceae thought to be basic in that family). Goodeniaceae have two features (tracheids, diffuse parenchyma) more primitive than corresponding conditions in Asteraceae and CaIyceraceae according to traditional criteria. Diversity in wood anatomy within Calyceraceae is explainable in terms of adaptation to particular ecological conditions. Although woods of the family as …
Nomenclatural Changes In Polemoniaceae, J. Mark Porter
Nomenclatural Changes In Polemoniaceae, J. Mark Porter
Aliso: A Journal of Systematic and Floristic Botany
Recent molecular phylogenetic analyses of nuclear, chloroplast and mitochondrial DNA of Polemoniaceae have prompted a reexamination of morphological data and a reassessment of current taxonomy. These studies prompt several nomenclatural changes in the family. Eight taxa formerly included in Gilia section Giliastrum are transferred to the genus Giliastrum. In addition, two new tribes of Polemoniaceae are recognized.
Phylogeny And Adaptation In The Encelia Alliance (Asteraceae: Helliantheae), Curtis Clark
Phylogeny And Adaptation In The Encelia Alliance (Asteraceae: Helliantheae), Curtis Clark
Aliso: A Journal of Systematic and Floristic Botany
The three related genera Encelia, Enceliopsis, and Geraea comprise the alliance. The first consists primarily of shrubs and the latter two of herbaceous perennials and an annual. With the exception of two Encelia species of arid South America, all inhabit southwestern North America. Enceliopsis and Geraea are sister groups, and together form the sister group to Encelia, which includes two major clades. Especially in Encelia, there are diverse morphologies and a variety of ecological strategies marked by differences in habitat, vestiture, water balance, and photosynthetic parameters. The North American species of all three genera are obligate …
A Coalescent Approach To Chloroplast Genome Relationships Within And Between Populations Of Pinus Devoniana In Mexico, Jennifer A. Matos
A Coalescent Approach To Chloroplast Genome Relationships Within And Between Populations Of Pinus Devoniana In Mexico, Jennifer A. Matos
Aliso: A Journal of Systematic and Floristic Botany
Pinus devoniana, a member of the Pinus montezumae complex (Ponderosae) of Mexico and Central America occurs as scattered populations from the western states of Jalisco and Nayarit to Chiapas in the east. Populations within regions, i.e., western or eastern Mexico, are separated by from 75 to 300 km, while the eastern and western populations are more that 700 km apart. Levels of gene flow between populations within regions and between eastern and western Mexico are assessed using the paternally inherited chloroplast genome as a marker. Twenty-five polymorphic restriction chloroplast sites were found in the 175 individuals surveyed; …
Cladistic Parsimony Analysis Of Internal Transcribed Spacer Region (Nrdna) Sequences Of Bouteloua And Relatives (Gramineae: Chloridoideae), J. Travis Columbus, Michael S. Kinney, Rashmi Pant, Maria Elena Siqueros Delgado
Cladistic Parsimony Analysis Of Internal Transcribed Spacer Region (Nrdna) Sequences Of Bouteloua And Relatives (Gramineae: Chloridoideae), J. Travis Columbus, Michael S. Kinney, Rashmi Pant, Maria Elena Siqueros Delgado
Aliso: A Journal of Systematic and Floristic Botany
Chloridoideae) employing cladistic parsimony analysis of nuclear ribosomal internal transcribed spacer region (ITS1 + 5.8S + ITS2) DNA sequences. Included were Aegopogon (2 of 4 species), Bouteloua (34 of 42), Buchloë (1 of 1), Buchlomimus (1 of 1), Cathestecum (2 of 4), Cyclostachya (1 of 1), Griffithsochloa (1 of 1), Hilaria (1 of 7), Opizia (2 of 2), Pentarrhaphis (2 of 3), Pleuraphis (2 of 3), Pringleochloa (1 of 1), Soderstromia (1 of 1), and five outgroup genera/species for a total of I8 genera, 56 species, and ten varieties. In all, the ITS region of 72 plants was sequenced and …
Plant Systematics: Beginnings And Endings, Billie L. Turner
Plant Systematics: Beginnings And Endings, Billie L. Turner
Aliso: A Journal of Systematic and Floristic Botany
No abstract provided.
Phylogenetic Relationships Of Polemoniaceae: Inferences From Mitochondrial Nad1b Intron Sequences, J. Mark Porter, Leigh A. Johnson
Phylogenetic Relationships Of Polemoniaceae: Inferences From Mitochondrial Nad1b Intron Sequences, J. Mark Porter, Leigh A. Johnson
Aliso: A Journal of Systematic and Floristic Botany
The most recent assessments of phylogenetic relationships and diversification in the flowering plant family Polemoniaceae have relied on nuclear ribosomal and chloroplast DNA sequences. We employed the mitochondrial nad1b intron, located within the second transcription unit of the first subunit of NADH dehydrogenase, for phylogenetic inference. Maximum parsimony analysis of these data provided evidence that Polemoniaceae are more closely related to families Fouquieriaceae, Diapensiaceae, Styracaceae, and Primulaceae than to families of the Solananae, where it has been classified. Fouquieriaceae are inferred to be the sister group of Polemoniaceae; however, when indels are treated as additional characters and given twice the …
Arabis Hirshbergiae (Brassicaceae), A Narrow Endemic From The Cuyamaca Mountains, San Diego County, California, Steve Boyd
Aliso: A Journal of Systematic and Floristic Botany
A narrow endemic from the Cuyamaca Mountains of southern California is described as a new species, Arabis hirshbergiae. Closest relationships appear to be with A. johnstonii and A. parishii, also narrow endemics from the San Jacinto and San Bernardino Mountains respectively. All three species are associated with pebble plain habitats in montane areas characterized by relatively gentle relief compared with surrounding canyons and ridge systems.
Magnetostratigraphy Of Cueva Del Aleman, Isla De Mona, Puerto Rico And The Species Duration Of Audobon's Shearwater, Bruce C. Panuska, John M. Mylroie, Darrell Armentrout, Donald A. Mcfarlane
Magnetostratigraphy Of Cueva Del Aleman, Isla De Mona, Puerto Rico And The Species Duration Of Audobon's Shearwater, Bruce C. Panuska, John M. Mylroie, Darrell Armentrout, Donald A. Mcfarlane
WM Keck Science Faculty Papers
Magnetostratigraphic analysis of deposits exposed in Cueva del Aleman shows two reversed and two normal chronozones. The lower normal polarity event is observed in a clastic dike and probably predates initial cave formation. Sediments deposited inside the cave proper show a R-N-R sequence and probably date to at least 1.8 Ma. A fossiliferous clastic dike contains normal polarity with an overlying reversed magnetozone. Audubon’s Shearwater (bird) bones occur in the dike, which is tentatively correlated with the lower N polarity zone predating cave formation. If this correlation is correct, the Audubon’s Shearwater (Puffinus lherminieri) range can be extended back to …
New Names And Combinations In Encelia Frutescens Sensu Lato (Asteraceae: Heliantheae, Curtis Clark
New Names And Combinations In Encelia Frutescens Sensu Lato (Asteraceae: Heliantheae, Curtis Clark
Aliso: A Journal of Systematic and Floristic Botany
No abstract provided.
Cheilanthoid Ferns (Pteridaceae: Cheilanthoideae) In The Southwestern United States And Adjacent Mexico-A Molecular Phylogenetic Reassessment Of Generic Lines, Gerald J. Gastony, David R. Rollo
Cheilanthoid Ferns (Pteridaceae: Cheilanthoideae) In The Southwestern United States And Adjacent Mexico-A Molecular Phylogenetic Reassessment Of Generic Lines, Gerald J. Gastony, David R. Rollo
Aliso: A Journal of Systematic and Floristic Botany
Cheilanthoids are the most commonly encountered fern species of the arid southwest and other xeric habitats throughout the world. Cheilanthes, Notholaena, Pellaea, and Bommeria are the best known southwestern genera, but some authors recognize segregate genera such as Argyrochosma, Aspidotis, Astrolepis, and Pentagramma. Others reject distinctions among some of these genera as artificial, leaving cheilanthoid generic concepts in a state of flux. This unsettled taxonomy is often attributed to morphological homoplasy associated with adaptation to xeric habitats, suggesting the need for new analyses that do not depend on potentially misleading morphology. Nucleotide sequences …
Ecophysiological Observations On Lane Mountain Milkvetch, Astragalus Jaegerianus (Fabaceae), A Proposed Endangered Species Of The Mojave Desert, Arthur C. Gibson, M. Rasoul Sharifi, Philip W. Rundel
Ecophysiological Observations On Lane Mountain Milkvetch, Astragalus Jaegerianus (Fabaceae), A Proposed Endangered Species Of The Mojave Desert, Arthur C. Gibson, M. Rasoul Sharifi, Philip W. Rundel
Aliso: A Journal of Systematic and Floristic Botany
Astragalus jaegerianus, the Lane Mountain milkvetch, a perennial herbaceous legume, is a rare and very narrow endemic of the central Mojave Desert in San Bernardino County, California, and currently proposed to be listed as an endangered species. This herb grows in the protection of low shrubs. Anatomical observations revealed that leaflets are amphistomatic and have isolateral mesophyll, typical of full-sun desert leaves, and the green stem is an important photosynthetic organ, having abundant stomata and a cylinder of cortical chlore nchyma. Ecophysiological studies showed that this species requires high PFD (1400-1500 μmol m-2s-1) to achieve …
Introduction, Edward L. Schneider, Roy L. Taylor
Introduction, Edward L. Schneider, Roy L. Taylor
Aliso: A Journal of Systematic and Floristic Botany
No abstract provided.
Aliciella, A Recircumscribed Genus Of Polemoniaceae, J. Mark Porter
Aliciella, A Recircumscribed Genus Of Polemoniaceae, J. Mark Porter
Aliso: A Journal of Systematic and Floristic Botany
Recent phylogenetic analyses within Polemoniaceae have provided evidence that the current circumscriptionof Gilia recognizes and gives taxonomic status to a polyphyletic assemblage of species. As a first step in rectifying this problem, the genus Aliciella Brand (Polemoniaceae) is resurrected and recircumscribed to include Gilia section Giliandra and Gilia subgenus Gilmania sensu Mason & Grant, a monophyletic (=holophyletic) group as here described. Twenty-one recombinations are proposed: Aliciella cespitosa, A. formosa, A. haydenii, A. haydenii subsp. crandallii, A. heterostyla, A. humillima, A. hutchinsifolia, A. latifolia, A. latifolia subsp. imperialis. A. leptomeria. A. lottiae. A. mcvickerae.A. micromeria. A. nyensis, A. pentstemonoides, A. …
Computers And Learning, William K. Purves, Mary E. Williams
Computers And Learning, William K. Purves, Mary E. Williams
All HMC Faculty Publications and Research
The important questions for instructors to address concern what skills the student is to learn and how the student is to be motivated to acquire those skills. Questions about simulations, graphics tools, and the like are unimportant until the first two questions have been answered adequately. We discuss the role of explanation by students and describe a mechanism for motivating students to learn.