Biology Commons^™

Extensive Dieback In Malosma Laurina In Coastal Exposures Of The Santa Monica Mountains Associated With Unprecedented Drought In California, Gina S. Gilderman, Kaitlyn E. Sauer, Gabriella Palmeri

Biology

Throughout coastal exposures of the Santa Monica Mountains (SMM) there is a recent emergence of widespread dieback in Laurel Sumac (Malosma laurina). M. laurina is a keystone species of chaparral that dominates the SMM. A significant trait of M. laurina is an extensive root system exceeding 12 m in depth. We hypothesized that M. laurina was weakened by unprecedented drought in California (2013-2015) and predisposed to fungal pathogens. An initial study conducted in the summer of 2015 revealed all stem samples taken from dieback adult M. laurina plants were infected with Botryosphaeria dothidea, while zero stem samples taken …

On Flavonoid Accumulation In Different Plant Parts: Variation Patterns Among Individuals And Populations In The Shore Campion (Silene Littorea), José C. Del Valle, Mª Luisa Buide, Inés Casimiro-Soriguer, Justen B. Whittall, Eduardo Narbona

Biology

The presence of anthocyanins in flowers and fruits is frequently attributed to attracting pollinators and dispersers. In vegetative organs, anthocyanins and other non-pigmented flavonoids such as flavones and flavonols may serve protective functions against UV radiation, cold, heat, drought, salinity, pathogens, and herbivores; thus, these compounds are usually produced as a plastic response to such stressors. Although, the independent accumulation of anthocyanins in reproductive and vegetative tissues is commonly postulated due to differential regulation, the accumulation of flavonoids within and among populations has never been thoroughly compared. Here, we investigated the shore campion (Silene littorea, Caryophyllaceae) which exhibits …

Novel Seed Germination In Response To California’S Historic Drought May Deplete Soil Seed Banks, Amanda M. Burns, Victoria M. Lekson, Helen I. Holmlund, Stephen D. Davis

Biology

We observed novel seed germination, without a fire cue, in an obligate seeding species of chaparral (Ceanothus megacarpus) during historic drought in California (2014). We hypothesized that premature germination was promoted by drought-induced canopy dieback among adults that allowed high radiation loads to reach normally shaded soils, cracking seed coats, facilitating water uptake. We hypothesized that because premature seed germination was late in the season (April, when December is typical) roots would not have time to penetrate deep moisture resources before the onset of summer drought, leading to excessive mortality and eventual depletion of soil seed banks. We …

Comparative Foliar Water Uptake And Leaf Hydrophobicity In Island Versus Mainland Ferns, Victoria M. Lekson, Helen I. Holmlund, Nicole A. Nakamatsu, Amanda M. Burns, Stephen D. Davis

Biology

In 2014, Southern California experienced the worst drought in the last 1,200 years. In this study, the mechanisms of drought tolerance for eight species of ferns in the Santa Monica Mountains were assessed with a focus on foliar water uptake and hydrophobicity of frond (leaf) surfaces. We measured gravimetric foliar water uptake and angle of contact for a drop of water on a frond. Seasonal shifts were tracked as a method of following drought response patterns.

Fog is becoming more important due to limited ground water. Fog is far more common on Santa Cruz Island off the coast of California …

The Non-Native Plant Rosa Multifl Ora Expresses Shade Avoidance Traits Under Low Light Availability, Rebecca E. Drenovsky, Daniel M. Dlugos, Hillary Collins, Elise M. Bartelme

Biology

PREMISE OF THE STUDY: Shade tolerance is a key trait promoting invasive plant performance in forest interiors. Rosa multifl ora is a problematic invasive shrub in the northeastern United States, occurring in edge habitats and encroaching into forests. Our objective was to evaluate the shade tolerance of R. multifl ora to assess how ecophysiological traits may facilitate its spread into forest interiors. METHODS: In the fi eld, we documented shrub and seed bank density, fecundity, phenology, and seasonal photosynthetic rates of R. multifl ora in contrasting light environments. In the greenhouse, we exposed seedlings to simulated canopy treatments by altering …

Nervous System Development In Lecithotrophic Larval And Juvenile Stages Of The Annelid Capitella Teleta, Néva P. Meyer, Allan Carrillo-Baltodano, Richard E. Moore, Elaine C. Seaver

Biology

Background: Reconstructing the evolutionary history of nervous systems requires an understanding of their architecture and development across diverse taxa. The spiralians encompass diverse body plans and organ systems, and within the spiralians, annelids exhibit a variety of morphologies, life histories, feeding modes and associated nervous systems, making them an ideal group for studying evolution of nervous systems. Results: We describe nervous system development in the annelid Capitella teleta (Blake JA, Grassle JP, Eckelbarger KJ. Capitella teleta, a new species designation for the opportunistic and experimental Capitella sp. I, with a review of the literature for confirmed records. Zoosymposia. 2009;2:25-53) using …

Degradation Of Bunker C Fuel Oil By White-Rot Fungi In Sawdust Cultures Suggests Potential Applications In Bioremediation, Darcy Young, James Rice, Rachael Martin, Erika Lindquist, Anna Lipzen, Igor Grigoriev, David Hibbett

Biology

Fungal lignocellulolytic enzymes are promising agents for oxidizing pollutants. This study investigated degradation of Number 6 "Bunker C" fuel oil compounds by the white-rot fungi Irpex lacteus, Trichaptum biforme, Phlebia radiata, Trametes versicolor, and Pleurotus ostreatus (Basidiomycota, Agaricomycetes). Averaging across all studied species, 98.1%, 48.6%, and 76.4% of the initial Bunker C C10 alkane, C14 alkane, and phenanthrene, respectively were degraded after 180 days of fungal growth on pine media. This study also investigated whether Bunker C oil induces changes in gene expression in the white-rot fungus Punctularia strigosozonata, for which a complete reference genome is available. After 20 days …

The Spinning Apparatus Of Webspinners – Functional-Morphology, Morphometrics And Spinning Behaviour, Sebastian Büsse, Thomas Hörnschemeyer, Kyle Hohu, David Mcmillan, Janice Edgerly-Rooks

Biology

Webspinners (Insecta: Embioptera) have a distinctly unique behaviour with related morphological characteristics. Producing silk with the basitarsomeres of their forelegs plays a crucial role in the lives of these insects – providing shelter and protection. The correlation between body size, morphology and morphometrics of the spinning apparatus and the spinning behaviour of Embioptera was investigated for seven species using state-of-the-art methodology for behavioural as well as for morphological approaches. Independent contrast analysis revealed correlations between morphometric characters and body size. Larger webspinners in this study have glands with greater reservoir volume, but in proportionally smaller tarsi relative to body size …

Convergent Losses Of Decay Mechanisms And Rapid Turnover Of Symbiosis Genes In Mycorrhizal Mutualists, Annegret Kohler, Alan Kuo, Laszlo G. Nagy, Emmanuelle Morin, Kerrie W. Barry, Francois Buscot, Björn Canbäck, Cindy Choi, Nicolas Cichocki, Alicia Clum, Jan Colpaert, Alex Copeland, Mauricio D. Costa, Jeanne Doré, Dimitrios Floudas, Gilles Gay, Mariangela Girlanda, Bernard Henrissat, Sylvie Herrmann, Jaqueline Hess, Nils Högberg, Tomas Johansson, Hassine Radhouane Khouja, Kurt Labutti, Urs Lahrmann, Anthony Levasseur, Erika A. Lindquist, Anna Lipzen, Roland Marmeisse, Elena Martino, Claude Murat, Chew Y. Ngan, David Hibbett

Biology

To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent …

Differential Survival Of Chaparral Shrub Species In Response To Severe Drought, Hannah Dario, Stephen D. Davis

Biology

In this experiment, we examined how the plants in the Santa Monica Mountains are responding to the driest period in recorded history for California. Our hypothesis was that plant species with the deepest roots would have highest survivorship. We thought this because deep-rooted shrubs will have greater access to soil moisture. This hypothesis was tested by collecting data on plant survival, in a mixed chaparral stand, containing eleven species, growing in the Green Valley Preserve off of Stunt road, in the Santa Monica Mountains. The chaparral stand was 21 years old, having last burned in 1993 (Old Topanga Canyon Fire). …

Clonal Integration In Ludwigia Hexapetala Under Different Light Regimes, Rebecca E. Drenovsky, R. E. Glover, C. J. Futrell, Brenda J. Grewell

Biology

Physiological integration among ramets of invasive plant species may support their colonization and spread in novel aquatic environments where growth-limiting resources are spatially heterogeneous. Under contrasting light conditions, we investigated how clonal integration influences growth, biomass allocation and morphology of Ludwigia hexapetala, an emergent floating-leaved macrophyte that is highly invasive in a range of wetland habitat types. In aquatic mesocosms, stolons of offspring ramets were either connected or severed from parent plants, with the pairs exposed to homogenous or heterogeneous combinations of sun or 85% shade. Morphological traits of all ramets were strongly influenced by light environment, and low …

Marz: An Algorithm To Combinatorially Analyze Gapped N-Mer Models Of Transcription Factor Binding, Rowan G. Zellers, Robert A. Drewell, Jacqueline M. Dresch

Biology

Background: A key challenge in understanding the molecular mechanisms that control gene regulation is the characterization of the specificity with which transcription factor proteins bind to specific DNA sequences. A number of computational approaches have been developed to examine these interactions, including simple mononucleotide and dinucleotide position weight matrix models. Results: Here we develop a novel, unbiased computational algorithm, MARZ, that systematically analyzes all possible gapped matrices across a fixed number of nucleotides. In addition, to evaluate the ability of these matrix models to predict in vivo binding sites, we utilize a new scoring system and, in combination with established …

Increased High-Density Lipoprotein Cholesterol Levels In Mice With Xx Versus Xy Sex Chromosomes, Jenny C. Link, Xuqi Chen, Christopher Prien, Mark S. Borja, Bradley Hammerson, Michael N. Oda, Arthur P. Arnold, Karen Reue

Biology

Objective—

The molecular mechanisms underlying sex differences in dyslipidemia are poorly understood. We aimed to distinguish genetic and hormonal regulators of sex differences in plasma lipid levels.

Approach and Results—

We assessed the role of gonadal hormones and sex chromosome complement on lipid levels using the four core genotypes mouse model (XX females, XX males, XY females, and XY males). In gonadally intact mice fed a chow diet, lipid levels were influenced by both male–female gonadal sex and XX–XY chromosome complement. Gonadectomy of adult mice revealed that the male–female differences are dependent on acute effects of gonadal hormones. In both …

Global Sensitivity Analysis Of A Dynamic Model For Gene Expression In Drosophila Embryos, Gregory D. Mccarthy, Robert A. Drewell, Jacqueline M. Dresch

Biology

It is well known that gene regulation is a tightly controlled process in early organismal development. However, the roles of key processes involved in this regulation, such as transcription and translation, are less well understood, and mathematical modeling approaches in this field are still in their infancy. In recent studies, biologists have taken precise measurements of protein and mRNA abundance to determine the relative contributions of key factors involved in regulating protein levels in mammalian cells. We now approach this question from a mathematical modeling perspective. In this study, we use a simple dynamic mathematical model that incorporates terms representing …

A Comparison Of The Caulobacter Na1000 And K31 Genomes Reveals Extensive Genome Rearrangements And Differences In Metabolic Potential, Craig Stephens, Kurt Ash, Theta Brown, Tynetta Watford, Latia E. Scott, Bert Ely

Biology

The genus Caulobacter is found in a variety of habitats and is known for its abilityto thrive in low-nutrient conditions. K31 is a novel Caulobacter isolate that has the ability to tolerate copper and chlorophenols, and can grow at 48Cwith a doubling time of 40 h. K31 contains a 5.5 Mb chromosome that codes for more than 5500 proteins and two large plasmids (234 and 178 kb) thatcode for 438 additional proteins. A comparison of the K31 and the Caulobactercrescentus NA1000 genomes revealed extensive rearrangements of gene order,suggesting that the genomes had been randomly scrambled. However, a careful analysis revealed …

Selenite Activates The Alternative Oxidase Pathway And Alters Primary Metabolism In Brassica Napus Roots: Evidence Of A Mitochondrial Stress Response, Aleksandar Dimkovikj, Doug Van Hoewyk

Biology

Background: Human requirements for dietary selenium are met mainly by crops. However, excessive uptake of selenium in plants can restrict growth, and its toxicity has been postulated to target roots. Selenite toxicity can be attributed to its assimilation into selenocysteine, which can replace cysteine to yield malformed selenoproteins. Additionally, selenite has pro-oxidant properties. In this study, the effects of selenite on root tissue in Brassica napus (canola) were investigated to better understand its mode of toxicity and the metabolic adjustments needed to mediate a selenite-response.Results: Selenite induced the rapid formation of mitochondrial superoxide, which led to decreased aconitase activity and …

Leaf Mechanical Strength Corresponds To Tissue Water Relations In Twelve Species Of California Ferns, Breahna M. Gillespie, Stephen D. Davis, Jarmila Pittermann

Biology

The dominant vegetation types in southern California’s coastal foothills are chaparral and costal sage scrub. Chaparral shrubs have mechanically strong evergreen leaves whereas coastal sage scrubs bear mechanical weak, facultative deciduous leaves. What about the ferns that live in the understory of these vegetation types, especially considering their adaptations to a summer dry, Mediterranean-type climate? We tested the hypothesis that some fern leaves are stronger than others and mechanically strong leaves are associated with greater dehydration tolerance. Twelve fern species were examined. Tissue water relations were assessed via pressure volume curves using Scholander-Hammel pressure chambers. We estimated osmotic potential at …

Relationship Between Dehydration Tolerance Of California Ferns And The Mechanical Strength Of Their Stipes, Helen I. Holmlund, Stephen D. Davis

Biology

In recent years, experts in plant physiology have begun to explore the functional traits of ferns, especially in regards to their tissue-water relations. However, to our knowledge, no scientist had yet examined the relationship between fern biomechanics and physiology. We examined the mechanical properties of fern stipes (stems) and attempted to relate those properties to ecological and physiological traits. Based on our knowledge of fern anatomy, we hypothesized that stipe mechanical strength would not correlate with water-stress resistance as it does in seed-bearing plants.

We assessed mechanical strength using Modulus of Elasticity (MOE) and tissue-water relations using pressure-volume curves. Water-stress …

Transcriptome Analysis Of A Petal Anthocyanin Polymorphism In The Arctic Mustard, Parrya Nudicaulis, Timothy Butler, Cynthia Dick, Matthew L. Carlson, Justen B. Whittall

Biology

Angiosperms are renown for their diversity of flower colors. Often considered adaptations to pollinators, the most common underlying pigments, anthocyanins, are also involved in plants’ stress response. Although the anthocyanin biosynthetic pathway is well characterized across many angiosperms and is composed of a few candidate genes, the consequences of blocking this pathway and producing white flowers has not been investigated at the transcriptome scale. We take a transcriptome-wide approach to compare expression differences between purple and white petal buds in the arctic mustard, Parrya nudicaulis, to determine which genes’ expression are consistently correlated with flower color. Using mRNASeq and de …

Biogeomorphology Of A Mojave Desert Landscape — Configurations And Feedbacks Of Abiotic And Biotic Land Surfaces During Landform Evolution, Rebecca E. Drenovsky, N. Pietrasiak, L. S. Santiago, R. C. Graham

Biology

Terrestrial ecosystems can be more holistically understood by investigating the morphology of landscape mosaics, the assemblage of their ecological communities, and the linkages and feedbacks between the mosaics and communities. The overarching objectives of this study were to: (1) study the abiotic and biotic configurations of landform units as mosaics within a Mojave Desert chronosequence; and (2) elucidate their potential feedbacks, interactions, and dynamics during landform evolution. Seven landform units distributed over three geomorphic ages were identified, including: young bars and swales; intermediate-aged flattened bars, flattened swales, and bioturbation units; and old desert pavements and shrub zones. These landform units …

Variation In Setal Micromechanics And Performance Of Two Gecko Species, Travis J. Hagey, Jonathan B. Puthoff, Madisen Holbrook, Luke J. Harmon, Kellar Autumn

Biology

Biomechanical models of the gecko adhesive system typically focus on setal mechanics from a single gecko species, Gekko gecko. In this study, we compared the predictions from three mathematical models to experimental observations considering an additional gecko species Phelsuma grandis, to quantify interspecific variation in setal micromechanics. We also considered the accuracy of our three focal models: the frictional adhesion model, work of detachment model, and the effective modulus model. Lastly, we report a novel approach to quantity the angle of toe detachment using the Weibull distribution. Our results suggested the coupling of frictional and adhesive forces in isolated setal …

Shell Shape Convergence Masks Biological Diversity In Gliding Scallops: Description Of Ylistrum N. Gen. (Pectinidae) From The Indo-Pacific Ocean, Alvin Alejandrino, Glené Mynhardt, Louise Puslednik, Joezen Corrales, Jeanne M. Serb

Biology

The scallop genus Amusium Röding, 1798 is one of few genera of Pectinidae that includes taxa capable of long-distance swimming or gliding. Membership of the genus has been defined primarily by shell shape, and it currently includes only three species: the type species A. pleuronectes (Linnaeus, 1758), A. balloti (Bernardi, 1861) and A. japonicum (Gmelin, 1791). In this study, we use molecular data and aspects of shell morphology to resolve the systematics of the genus. Phylogenetic reconstruction of Pectinidae using nuclear and mitochondrial DNA sequence from four genes supports a polyphyletic Amusium. Differences in internal ribbing pattern provide morphological …

Southern Flounder (Paralichthys Lethostigma) Stock Structure Inferred From Otolith Shape Analysis, Stephen R. Midway, Steven X. Cadrin, Frederick S. Scharf

Biology

Examination of otolith morphometric variation has been shown to provide improved descriptions of stock structure for several marine fish species. We examined spatial variation in otolith shape of southern flounder (Paralichthys lethostigma) to understand population structure at the following geographic levels: ocean basin (Atlantic and Gulf of Mexico); regional coastal waters (Texas, Florida) and (Georgia, South Carolina); and local coastal waters (North Carolina). To reduce variability, we considered only age- 1 female fish. From digitized otolith images, we extracted descriptions for common shape indices and elliptical Fourier coefficients and found strong evidence for differences at the ocean basin scale, but …

The Ubiquitin-Proteasome Pathway Protects Chlamydomonas Reinhardtii Against Selenite Toxicity, But Is Impaired As Reactive Oxygen Species Accumulate, Patrick Vallentine, Chiu Yueh Hung, Jiahua Xie, Doug Van Hoewyk

Biology

The ubiquitin-proteasome pathway (UPP) coordinates a myriad of physiological processes in higher plants, including abiotic stress responses, but it is less well characterized in algal species. In this study, the green alga Chlamydomonas reinhardtii was used to gain insights into the role of the UPP during moderate and severe selenite stress at three different time points. The data indicate that activity of the UPP in response to selenium (Se) stress was both time and dose dependent. Moderate selenite stress increased proteasome activity, protein ubiquitination and the proteasomal removal of malformed selenoproteins. However, severe Se stress caused by prolonged selenite treatment …

Sexual Harassment And Feeding Inhibition Between Two Invasive Dengue Vectors, John Soghigian, Kathryn Gibbs, Ashleigh Stanton, Rachel Kaiser, Todd Livdahl

Biology

Two invasive mosquitoes, Aedes aegypti and Aedes albopictus, have been interacting during the course of a rapid range expansion by A. albopictus. We investigated the potential for interspecific feeding interference by male mosquitoes interacting with females within and between these species. A. aegypti feeding on both sugar and blood was suppressed when females of this species were exposed to A. albopictus males, but no change was observed when exposed to conspecifics. A. albopictus feeding was not affected by males of either species. The potential consequences of these behaviors are discussed within the context of other known interspecific effects, all of …

Gene Expression Studies For The Analysis Of Domoic Acid Production In The Marine Diatom Pseudo-Nitzschia Multiseries, Katie R. Boissonneault, Brooks M. Henningsen, Stephen S. Bates, Deborah L. Robertson, Sean Milton, Jerry Pelletier, Deborah A. Hogan, David E. Housman

Biology

Background: Pseudo-nitzschia multiseries Hasle (Hasle) (Ps-n) is distinctive among the ecologically important marine diatoms because it produces the neurotoxin domoic acid. Although the biology of Ps-n has been investigated intensely, the characterization of the genes and biochemical pathways leading to domoic acid biosynthesis has been limited. To identify transcripts whose levels correlate with domoic acid production, we analyzed Ps-n under conditions of high and low domoic acid production by cDNA microarray technology and reverse-transcription quantitative PCR (RT-qPCR) methods. Our goals included identifying and validating robust reference genes for Ps-n RNA expression analysis under these conditions. Results: Through microarray analysis of …

Choreography Of Silk Spinning Behavior In Webspinners (Embioptera): Phylogenetic Signal Or A Microhabitat Dance?, Janice Edgerly-Rooks

Biology

Silk spinning defines the morphologically constrained embiopterans. All individuals spin for protection, including immatures, adult males and the wingless females. Enlarged front tarsi are packed with silk glands and clothed with ejectors. They spin by stepping with their front feet and releasing silk against substrates and onto pre-existing silk, often cloth-like. Spinning is stereotypical and appears to differ between species in frequency and probability of transition between two spin-step positions. This spinning choreography was assessed using thousands of spin-steps scored in the laboratory for 22 species to test (1) the body size hypothesis predicting that spinning would be more complex …

Lost Branches On The Tree Of Life, Bryan T. Drew, Romina Gazis, Patricia Cabezas, Kristen S. Swithers, Jiabin Deng, Roseana Rodriguez, Laura A. Katz, Keith A. Crandall, David S. Hibbett, Douglas E. Soltis

Biology

Until recently, uploading sequences to GenBank (or EMBL) was generally considered sufficient to ensure reproducibility of phylogenetic studies using DNA sequence data. Increasingly, however, the systematics community is realizing that archiving raw DNA sequences is not adequate, and that the underlying alignments of DNA sequences as well as the resulting phylogenetic trees are pivotal for reproducibility, comparative purposes, meta-analyses, and ultimately synthesis. Indeed, there has been a growing clamor for journals to adopt and enforce more rigorous data archiving practices across diverse disciplines [4]–[8]. As a result, about 35 evolutionary journals [5],[9] have adopted policies …

Mechanics, Diversity, And Ecology Of Gecko Adhesion, Travis Jay Hagey

Biology

The question of why animals are shaped the way they are has intrigued scientists for hundreds of years. Studies of ecological morphology (the relationship between an organism’s form, function, and environment) often bridge multiple disciplines including biomechanics, ecology, phylogenetics, and comparative methods. In this dissertation, I gathered data and tested hypotheses that considered the link between morphology and performance and the relationship between performance and ecology. I focused my research on the adhesive abilities of geckos. Geckos are an understudied, diverse group of lizards, well known for their adhesive toe pads. I propose that geckos are an excellent group to …

Metabolic Impact Of Sex Chromosomes, Jenny Link, Xuqi Chen, Arthur P. Arnold, Karen Reue

Biology

Obesity and associated metabolic diseases are sexually dimorphic. To provide better diagnosis and treatment for both sexes, it is of interest to identify the factors that underlie male/female differences in obesity. Traditionally, sexual dimorphism has been attributed to effects of gonadal hormones, which influence numerous metabolic processes. However, the XX/XY sex chromosome complement is an additional factor that may play a role. Recent data using the four core genotypes mouse model have revealed that sex chromosome complement—independently from gonadal sex—plays a role in adiposity, feeding behavior, fatty liver and glucose homeostasis. Potential mechanisms for the effects of sex chromosome complement …