Biology Commons^™

Plasticity In Cavitation Resistance And Mechanical Strength Of Stem Xylem In Heteromeles Arbutifolia, Adults Versus Post-Fire Resprouts, Iolana N. Kaneakua, B. A. Bergman, F. W. Ewers, S. D. Davis

Biology

Background/Questions/Methods

Many species of chaparral shrubs of California undergo vigorous resprout success after wildfire. We hypothesized that the water transport properties of resprouts, as well as their biomechanical strength would differ from adults. In addition, we hypothesized that irrigated and shaded resprouts would display reduced cavitation resistance and biomechanical strength in comparison to controls and adults. We tested these hypotheses by using a centrifuge method to compare the vulnerability of xylem to water stress induced cavitation. We used 50% loss in hydraulic conductivity due to water stress (PLC₅₀) as our estimate of vulnerability to cavitation. A Universal Materials …

Molecular Evolution Of Glutamine Synthetase Ii: Phylogenetic Evidence Of A Non-Endosymbiotic Gene Transfer Event Early In Plant Evolution, Sohini Ghoshroy, Manfred Binder, Aurélien Tartar, Deborah L. Robertson

Biology

Background. Glutamine synthetase (GS) is essential for ammonium assimilation and the biosynthesis of glutamine. The three GS gene families (GSI, GSII, and GSIII) are represented in both prokaryotic and eukaryotic organisms. In this study, we examined the evolutionary relationship of GSII from eubacterial and eukaryotic lineages and present robust phylogenetic evidence that GSII was transferred from -Proteobacteria (Eubacteria) to the Chloroplastida. Results. GSII sequences were isolated from four species of green algae (Trebouxiophyceae), and additional green algal (Chlorophyceae and Prasinophytae) and streptophyte (Charales, Desmidiales, Bryophyta, Marchantiophyta, Lycopodiophyta and Tracheophyta) sequences were obtained from public databases. In Bayesian and maximum likelihood …

Cruise Foraging Of Invasive Chameleon (Chamaeleo Jacksonii Xantholophus) In Hawai’I, Travis J. Hagey, Jonathan B. Losos, Luke Harmon

Biology

We quantified the foraging behavior of the Jackson’s chameleon (Chamaeleo jacksonii xantholophus), an invasive insectivorous lizard species in Hawai’i. Using video taken in the field, we focused on percent time moving, moves per minute, and movement speeds. Our results supported previous findings that chameleons are ‘‘cruise foragers’’ (sensu Butler, 2005), a foraging behavior unlike almost all other species of lizards.

Ecological Opportunity And The Origin Of Adaptive Radiations, J. B. Yoder, E. Clancey, S. Des Roches, J. M. Eastman, L. Gentry, W. Godsoe, T. J. Hagey, D. Jochimsen, B. P. Oswald, J. Robertson, B. Sarver, J. J. Schenk, S. F. Spear, L. J. Harmon

Biology

Ecological opportunity – through entry into a new environment, the origin of a key innovation or extinction of antagonists – is widely thought to link ecological population dynamics to evolutionary diversification. The population-level processes arising from ecological opportunity are well documented under the concept of ecological release. However, there is little consensus as to how these processes promote phenotypic diversification, rapid speciation and adaptive radiation. We propose that ecological opportunity could promote adaptive radiation by generating specific changes to the selective regimes acting on natural populations, both by relaxing effective stabilizing selection and by creating conditions that ultimately generate diversifying …

Land Use And Climatic Factors Structure Regional Patterns In Soil Microbialcommunities, Rebecca E. Drenovsky, Kerri L. Steenworth, Louise E. Jackson, Kate M. Scow

Biology

Aim Although patterns are emerging for macroorganisms, we have limited under- standing of the factors determining soil microbial community composition and productivity at large spatial extents. The overall objective of this study was to discern the drivers of microbial community composition at the extent of biogeo- graphical provinces and regions. We hypothesized that factors associated with land use and climate would drive soil microbial community composition and biomass. Location Great Basin Province, Desert Province and California Floristic Province, California, USA. Methods Using phospholipid fatty acid analysis, we compared microbial com- munities across eight land-use types sampled throughout the State of …

Plant Community And Tissue Chemistry Responses To Fertilizer And Litter Nutrient Manipulations In A Temperate Grassland, Rebecca E. Drenovsky, Jean J. Pan, Brittany Widner, Deborah Ammerman

Biology

Human-mediated nutrient amendments have widespread effects on plant communities. One of the major consequences has been the loss of species diversity under increased nutrient inputs. The loss of species can be functional group dependent with certain functional groups being more prone to decline than others. We present results from the sixth year of a long-term fertilization and litter manipulation study in an old-field grassland. We measured plant tissue chemistry (C:N ratio) to understand the role of plant physiological responses in the increase or decline of functional groups under nutrient manipulations. Fertilized plots had significantly more total aboveground biomass and live …

Foraging Preference By Wild Deer On Toyon Populations From Santa Catalina Island Versus The Santa Monica Mountains, Amelia I. Clark, Rodney Honeycutt, Anjel Helms, Stephen Davis

Biology

Post-fire regeneration of Toyon (Heteromeles arbutifolia), a chaparral shrub on Santa Catalina Island is impeded by mule deer (Odocoileus hemionus), a non-native species introduced during the 1930’s. Mainland and island populations of Toyon were examined for potential differences in defense mechanisms that act as natural deterrents to over-browsing by ungulate herbivores, with the hypothesis that island populations, void of natural ungulate herbivores, may lack such defense mechanisms. Several characteristics of leaf morphology, including number and length of spines, leaf area and depth, and tensile strength of leaves, were compared between island and mainland populations. Leaves of Toyon from Santa Catalina …

Spatial And Seasonal Variations In Mercury Methylation And Microbial Community Structure In A Historic Mercury Mining Area, Yolo County, California, J. M. Holloway, M. B. Goldhaber, K. M. Scow, Rebecca E. Drenovsky

Biology

The relationships between soil parent lithology, nutrient concentrations, microbial biomass and community structure were evaluated in soils from a small watershed impacted by historic Hg mining. Upland and wetland soils, stream sediments and tailings were collected and analyzed for nutrients (DOC, SO4=, NO3−), Hg, MeHg, and phospholipid fatty acids (PLFA). Stream sediment was derived from serpentinite, siltstone, volcanic rocks and mineralized serpentine with cinnabar, metacinnabar and other Hg phases. Soils from different parent materials had distinct PLFA biomass and community structures that are related to nutrient concentrations and toxicity effects of trace metals including Hg. The formation of MeHg appears …

The Four-And-A-Half Lim Domain Protein 2 Regulates Vascular Smooth Muscle Phenotype And Vascular Tone, Nicole A. Neuman, Susan Ma, Gavin R. Schnitzler, Yan Zhu, Giorgio Lagna, Akiko Hata

Biology

In responsetovascular injury, differentiated vascular smooth muscle cells (vSMCs) undergo a uniqueprocess knownas“phenotype modulation,” transitioning from a quiescent, “contractile” phenotype to a proliferative, “synthetic” state. We have demonstrated previously that the signaling pathway of bone morphogenetic proteins, members of the transforming growth factor family, play a role in the induction and maintenance of a contractile phenotype in human primary pulmonary artery smooth muscle cells. In this study, we show that a four-and-ahalf LIM domainprotein 2(FHL2)inhibits transcriptional activation ofvSMC-specificgenesmediatedbythebonemorphogenetic protein signaling pathway through the CArG box-binding proteins, such as serum response factor and members of the myocardin (Myocd) family. Interestingly, FHL2 …

The Relative Ages Of Ectomycorrhizal Mushrooms And Their Plant Hosts Estimated Using Bayesian Relaxed Molecular Clock Analyses, David S. Hibbett, P. Brandon Matheny

Biology

Background: Ectomycorrhizae (ECM) are symbioses formed by polyphyletic assemblages of fungi (mostly Agaricomycetes) and plants (mostly Pinaceae and angiosperms in the rosid clade). Efforts to reconstruct the evolution of the ECM habit in Agaricomycetes have yielded vastly different results, ranging from scenarios with many relatively recent origins of the symbiosis and no reversals to the free-living condition; a single ancient origin of ECM and many subsequent transitions to the free-living condition; or multiple gains and losses of the association. To test the plausibility of these scenarios, we performed Bayesian relaxed molecular clock analyses including fungi, plants, and other eukaryotes, based …

Induction Of Microrna-221 By Platelet-Derived Growth Factor Signaling Is Critical For Modulation Of Vascular Smooth Muscle Phenotype, Brandi N. Davis, Aaron C. Hilyard, Peter H. Nguyen, Giorgio Lagna, Akiko Hata

Biology

The platelet-derived growth factor (PDGF) signaling pathway is a critical regulator of animal development and homeostasis. Activation of the PDGF pathway leads to neointimal proliferative responses to artery injury; it promotes a switch of vascular smooth muscle cells (vSMC) to a less contractile phenotype by inhibiting the SMC-specific gene expression and increasing the rate of proliferation and migration. The molecular mechanism for these pleiotropic effects of PDGFs has not been fully described. Here, we identify the microRNA-221 (miR-221), a small noncoding RNA, as a modulator of the phenotypic change of vSMCs in response to PDGF signaling. We demonstrate that miR-221 …

Host Density And Human Activities Mediate Increased Parasite Prevalence And Richness In Primates Threatened By Habitat Loss And Fragmentation, David N. M. Mbora, Mark A. Mcpeek

Biology

1. Habitat loss and fragmentation are the principal causes of the loss of biological diversity. In addition, parasitic diseases are an emerging threat to many animals. Nevertheless, relatively few studies have tested how habitat loss and fragmentation influence the prevalence and richness of parasites in animals. 2. Several studies of nonhuman primates have shown that measures of human activity and forest fragmentation correlate with parasitism in primates. However, these studies have not tested for the ecological mechanism(s) by which human activities or forest fragmentation influence the prevalence and richness of parasites. 3. We tested the hypothesis that increased host density …

Environmental Stress And Genetics Influence Night-Time Leaf Conductance In The C4 Grass Distichlis Spicata, Rebecca E. Drenovsky, Mairgareth A. Christman, Jeremy J. James, James H. Richards

Biology

Growing awareness of night-time leaf conductance (gnight) in many species, as well as genetic variation in gnight within several species, has raised questions about how genetic variation and environmental stress interact to influence the magnitude of gnight. The objective of this study was to investigate how genotype salt tolerance and salinity stress affect gnight for saltgrass [Distichlis spicata (L.) Greene]. Across genotypes and treatments, night-time water loss rates were 5–20% of daytime rates. Despite growth declining 37–87% in the high salinity treatments (300 mM and 600 mM NaCl), neither treatment had any effect on gnight in four of the six …

The Biological Soil Crusts Of The San Nicolas Island: Enigmatic Algae From A Geographically Isolated Ecosystem, Valerie R. Flechtner, Jeffrey R. Johansen, Jayne Belnap

Biology

Composite soil samples front 7 sites on San Nieolas Island were evaluated quantitatively and qualitatively for the presence of cyanobacteria and enkaryotic microalgae. Combined data demonstrated a rich algal flora with 19 cyanobacterial and 19 eukaryotic microalgal genera being identified, for a total of 56 species. Nine new species were identified and described among the cyanobacteria and the enkaryotic microalgae that were isolated: Leibleinia edaphica, Aphanothece maritima, Chroococcidiopsis edaphica, Cyanosarcina atroceneta, Hassallia californica, Hassallia pseudo-ramosissima, Microchaete terrestre, Palmellopsis californicus, and Pseudotetracystis compactis. Distinct distributional patterns of algal taxa existed among sites on the island and among soil algal floras of …

Shrub-Interspace Dynamics Alter Relationships Between Microbial Community Composition And Belowground Ecosystem Characteristics, Rebecca E. Drenovsky, Z. T. Aanderud, M. I. Shuldman, J. H. Richards

Biology

In desert ecosystems, belowground characteristics are influenced chiefly by the formation and persistence of “shrub-islands of fertility” in contrast to barren plant interspaces. If soil microbial communities are exclusively compared between these two biogeochemically distinct soil types, the impact of characteristics altered by shrub species, especially soil C and N, are likely to be overemphasized and overshadow the role of other characteristics in structuring microbial composition. To determine how belowground characteristics influence microbial community composition, and if the relative importance of these characteristics shifts across the landscape (i.e., between and within shrub and interspace soils), changes in microbial communities across …

Soil Morphology, Depth And Grapevine Root Frequency Influence Microbial Communities In A Pinot Noir Vineyard, Rebecca E. Drenovsky, K. L. Steenwerth, J. J. Lambert, D. A. Kluepfel, K. M. Scow, D. R. Smart

Biology

The composition of microbial communities responds to soil resource availability, and has been shown to vary with increasing depth in the soil profile. Soil microorganisms partly rely on root-derived carbon (C) for growth and activity. Roots in woody perennial systems like vineyards have a deeper vertical distribution than grasslands and annual agriculture. Thus, we hypothesized that vineyard soil microbial communities along a vertical soil profile would differ from those observed in grassland and annual agricultural systems. In a Pinot noir vineyard, soil pits were excavated to ca. 1.6–2.5m, and microbial community composition in ‘bulk’ (i.e., no roots) and ‘root’ (i.e., …

Variation In Resource Acquisition And Utilization Traits Between Native And Invasive Perennial Forbs, Rebecca E. Drenovsky, Christina E. Martin, Molly R. Falasco, Jeremy J. James

Biology

Understanding the functional traits that allow invasives to outperform natives is a necessary first step in improving our ability to predict and manage the spread of invaders. In nutrient-limited systems, plant competitive ability is expected to be closely tied to the ability of a plant to exploit nutrient-rich microsites and use these captured nutrients efficiently. The broad objective of this work was to compare the ability of native and invasive perennial forbs to acquire and use nutrients from nutrient-rich microsites. We evaluated morphological and physiological responses among four native and four invasive species exposed to heterogeneous (patch) or homogeneous (control) …

New And Current Microbiological Tools For Ecosystem Ecologists: Towards A Goal Of Linking Structure And Function, Rebecca E. Drenovsky, Kevin P. Ferris, Katharine M. Batten, Krassimira Hristova

Biology

Interest in the relationships between soil microbial communities and ecosystem functions is growing with increasing recognition of the key roles microorganisms play in a variety of ecosystems. With a wealth of microbial methods now available, selecting the most appropriate method can be daunting, especially to those new to the field of microbial ecology. In this review, we highlight those methods currently used and most applicable to ecological studies, including assays to study various aspects of the carbon and nitrogen cycles (e.g., pool dilution, acetylene reduction, enzyme analyses, among others), methods to assess microbial community composition (e.g., phospholipid fatty acid analysis …

Diatom Species Composition And Ecology Of The Animas River Watershed, Colorado, Usa, Gerald V. Sgro, John B. Poole, Jeffrey R. Johansen

Biology

The diatom flora of selected sites in the Animas River Watershed, San Juan County, Colorado, was studied. Eighty diatom taxa were identified from 10 sites: 8 sites on the Animas River and 1 site each on the Cement and Cascade tributaries. The sample diatom abundance was dominated by Achnanthidium minutissimum, Encyonema silesiacum, Aulacoseira distans, Hannaea arcus, and Diatoma mesodon. The presence of teratologic specimens of Fragilaria and Achnanthidium in the samples indicated the possibility of metals contamination. Diatom diversity was low and Lange-Bertalot pollution index scores indicated little organic pollution evidenced from diatom composition. There was evidence that diatom composition …

The Ecological Boundaries Of Six Carolina Bays: Community Composition And Ecotone Distribution, Lorrie Laliberte, James O. Luken, John J. Hutchens Jr., Kevin S. Godwin

Biology

Community and environmental gradients within the ecological boundaries of Carolina bay wetlands may provide important information on the interaction between Carolina bays and associated uplands, and may also provide guidance for improved management. We established twelve 30-m transects on the sloping rims of each of six Carolina bays in northeastern South Carolina to characterize the community gradient, as well as important environmental factors producing this gradient. Mid-points of the transects were placed on jurisdictional wetland boundaries. Hydrology, soil properties, and plant species composition were measured within these transects. On average, transects included an elevation change of 0.6 m that corresponded …

Horizontal Transfer Of A Nitrate Assimilation Gene Cluster And Ecological Transitions In Fungi: A Phylogenetic Study, Jason C. Slot, David S. Hibbett

Biology

High affinity nitrate assimilation genes in fungi occur in a cluster (fHANT-AC) that can be coordinately regulated. The clustered genes include nrt2, which codes for a high affinity nitrate transporter; euknr, which codes for nitrate reductase; and NAD(P)H-nir, which codes for nitrite reductase. Homologs of genes in the fHANT-AC occur in other eukaryotes and prokaryotes, but they have only been found clustered in the oomycete Phytophthora (heterokonts). We performed independent and concatenated phylogenetic analyses of homologs of all three genes in the fHANT-AC. Phylogenetic analyses limited to fungal sequences suggest that the fHANT-AC has been transferred horizontally from a basidiomycete …

A Historic Perspective: The Response Of Breeding Passerines To Rangeland Alteration In Rich County, Utah, Lindsay J. Brown

Biology

Shrub-dominated ecosystems on private lands are important rangeland resources through much of the western U.S., including Rich County, Utah. Because of its important role in livestock production, this shrubsteppe ecosystem has been exposed to a variety of sagebrush removal methods. Little is known about the relative effects of chemical, mechanical, or burn treatments on breeding passerine communities. Furthermore, most studies address only short-term effects. We studied breeding passerine communities and vegetation on 17 untreated sites and 49 range sites treated between 1962 and 2004 to examine the effects of treatment type and treatment age. The sagebrush treatments produced considerable changes …

Effects Of Environmental Conditions And Insect Life Stages On Performance Of Entomopathogenic Nematodes For Suppression Of Plum Curculio, Conotrachelus Nenuphar (Coleoptera: Curculionidae), In Northern Utah, Hong Geun Kim

Biology

In a series of field and laboratory experiments, I tested two entomopathogenic nematode species, two nematode concentrations, and three life stages of the economically damaging insect pest, Contrachelus nenuphar, to support the development of a biological control program for this pest in northern Utah. Two entomopathogenic nematodes, Heterorhabditis bacteriophora and Steinernema feltiae, were tested for their virulence. The population of H. bacteriophora tested was collected from soil infested with plum curculio in Brigham City, UT in 2002. The S. feltiae population was obtained from a commercial source. In temperature bioassays, the two nematodes species exhibited different thermal ranges. …

Structural Evolution Of Fern Chloroplast Genomes, Jessie M. Roper

Biology

The circular chloroplast genome map of land plants is generally conserved with respect to gene content and organization. However, sufficient variation also exists to allow phylogenetic information to be gleaned from the molecule. The ferns exhibit a highly rearranged gene order in and around the inverted repeat which appeared to hold phylogenetically useful information. To test the usefulness of these rearrangement events I first sequenced the complete plastid genome sequence of the marratioid fern Angiopteris. I then used the complete chloroplast genome sequences of the ferns Adiantum and Angiopteris to design alternative sets of Long-PCR primers within genes contained …

Screening Candidate Fungicides For Control Of Chalkbrood Disease In Alfalfa Leafcutting Bees, Megachile Rotundata (F.) (Hymenoptera: Megachilidae), Craig Huntzinger

Biology

Pollination of alfalfa seed crops is done primarily by managed populations of the alfalfa leafcutting bee, Megachile rotundata (F.). One of the biggest problems associated with managing M. rotundata on a commercial scale is a fungal disease called chalkbrood, caused by Ascosphaera aggregata Skou. The disease infects larvae that have consumed pollen and nectar contaminated with fungal spores. The spores germinate in the bee's gut, spreading hyphae throughout the host and killing the bee. Mortality from chalkbrood is regularly 10% to 35% in the northwestern United States, and infection levels in excess of 50% are not uncommon. As a consequence, …

The Role Of Individual-Level Behavior: From Safe Passage To Self-Organization, Bertrand H. Lemasson

Biology

A considerable amount of research in fisheries exists to assess and predict the success rate of fish attempting to navigate through artificial barriers in their environment. Such barriers typically include dams, culverts, power plants, and pumping stations. This dissertation contributes to fisheries science, and general ecology, by determining how individual-level behavior affects the movement decisions of solitary fish and how simple inter-individual interactions can generate complex forms of collective behavior. The current research improves our ability to model small-scale movement patterns, such as those expected within the artificial restrictions of a water diversion facility, and provides insight into the communication …

The Pollination Ecology Of Hedysarum Boreale Nutt. (Fabaceae) And Evaluation Of Its Pollinating Bees For Restoration Seed Production, Katharine A. Swoboda

Biology

Federal land managers desire a consistent and cost-effective source of Hedysarum boreale Nutt. seed for rangeland restoration in the Great Basin and adjacent ecosystems. The breeding biology of H. boreale was assessed via hand pollination experiments at 2 sites in Cache County, Utah, USA in 2003. H. boreale was found to be self-compatible, but did not produce fruit and seeds in the absence of bee visitors. Xenogamy (out-crossing) treatments resulted in increased seed viability and decreased predispersal reproductive attrition. H. boreale was found to be homogamous during 2004 experiments designed to determine the timing and duration of stigma receptivity. H. …

Invasion By Aegilops Triuncialis (Barb Goatgrass) Slows Carbon And Nutrient Cycling In A Serpentine Grassland, Rebecca E. Drenovsky, Katharine M. Batton

Biology

Invasive plant species alter plant community composition and ecosystem function. In the United States, California native grasslands have been displaced almost completely by invasive annual grasses, with serpentine grasslands being one of the few remaining refugia for California grasslands. This study examined how the invasive annual grass, Aegilops triuncialis, has altered decomposition processes in a serpentine annual grassland. Our objectives were to (1) assess howA. triuncialis alters primary productivity and litter tissue chemistry, (2) determine whether A. triuncialis litter is more recalcitrant to decomposition than native litter, and (3) evaluate whether differences in the soil microbial community in A. triuncialis-invaded …

Performance Of Dionaea Muscipula As Influenced By Developing Vegetation, James O. Luken

Biology

Demography, growth, and flowering of Dionaea muscipula (Venus' fly trap) were studied during three years (2003–2005) following prescribed fire. Data were collected in permanent quadrats where the developing vegetation was either repeatedly clipped or allowed to grow. Clipping increased light availability at the soil surface. Over the study period, seedling establishment and flowering declined with increasing time since the last prescribed burn. Seedling densities did not differ between clipped and control quadrats, although greater numbers of seedlings grew to adult size in control quadrats and this significantly influenced population size-class structure. Clipping had no effect on leaf number or senescence, …

Influence Of Resource Pulses And Perennial Neighbors On The Establishment Of An Invasive Annual Grass In The Mojave Desert, Rebecca E. Drenovsky, J. J. James, M. A. Caird, R. L. Sheley

Biology

Invasion by exotic annual grasses is one of the most significant threats to arid ecosystems in the western USA. Current theories of invasibility predict plant communities become more susceptible to invasion whenever there is an increase in the amount of unused resources. The objective of this field study was to examine how resource pulses and temporal variation in resource demand by the native shrub vegetation influences establishment of the invasive annual grass Schismus arabicus. Water and nitrogen were applied as pulses in early spring, mid-spring, or continuously throughout the growing season to plots containing either Atriplex confertifolia or Atriplex …