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Articles 2371 - 2400 of 3460

Full-Text Articles in Ecology and Evolutionary Biology

Cryptic Diversity And Conservation Of Gopher Frogs Across The Southeastern United States, Stephen C. Richter, Eric M. O’Neill, Schyler O. Nunziata, Andrew Rumments, Emily S. Gustin, Jeanne E. Young, Brian I. Crother Jun 2014

Cryptic Diversity And Conservation Of Gopher Frogs Across The Southeastern United States, Stephen C. Richter, Eric M. O’Neill, Schyler O. Nunziata, Andrew Rumments, Emily S. Gustin, Jeanne E. Young, Brian I. Crother

Biological Sciences Faculty and Staff Research

Identifying cryptic biodiversity is fundamental to evolutionary biology and to conservation efforts. This study investigated range-wide genetic diversity of Gopher Frogs, Lithobates capito, across the southeastern United States coastal plain to determine implications for taxonomy and conservation. We collected data for two mtDNA regions in 21 populations to identify genetic structure across the geographic distribution of the species. Based on population genetic, phylogenetic, and genealogical analyses, we recovered three reciprocally monophyletic mtDNA lineages corresponding to mainland coastal plain populations and two lineages within peninsular Florida. Breakpoints for these lineages did not occur in previously identified hotspots of amphibian phylogeographic breaks …


Pparγ Negatively Regulates T Cell Activation To Prevent Follicular Helper T Cells And Germinal Center Formation, Hong-Jai Park, Do-Hyun Kim, Jin-Young Choi, Won-Ju Kim, Ji Yun Kim, Ali Senejani, Soo Seok Hwang, Lark Kyun Kim, Zuzana Tobiasova, Gap Ryol Lee, Joseph Craft, Alfred L.M. Bothwell, Je-Min Choi Jun 2014

Pparγ Negatively Regulates T Cell Activation To Prevent Follicular Helper T Cells And Germinal Center Formation, Hong-Jai Park, Do-Hyun Kim, Jin-Young Choi, Won-Ju Kim, Ji Yun Kim, Ali Senejani, Soo Seok Hwang, Lark Kyun Kim, Zuzana Tobiasova, Gap Ryol Lee, Joseph Craft, Alfred L.M. Bothwell, Je-Min Choi

Biology and Environmental Science Faculty Publications

Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor that regulates lipid and glucose metabolism. Although studies of PPARγ ligands have demonstrated its regulatory functions in inflammation and adaptive immunity, its intrinsic role in T cells and autoimmunity has yet to be fully elucidated. Here we used CD4- PPARγ KO mice to investigate PPARγ -deficient T cells, which were hyper-reactive to produce higher levels of cytokines and exhibited greater proliferation than wild type T cells with increased ERK and AKT phosphorylation. Diminished expression of IκΒα, Sirt1, and Foxo1, which are inhibitors of NF-κΒ, was observed in PPARγ-deficient T cells that …


Divergent Transcriptional Responses To Low Temperature Among Populations Of Alpine And Lowland Species Of New Zealand Stick Insects (Micrarchus)., Luke T Dunning, Alice B Dennis, Brent J Sinclair, Richard D Newcomb, Thomas R Buckley Jun 2014

Divergent Transcriptional Responses To Low Temperature Among Populations Of Alpine And Lowland Species Of New Zealand Stick Insects (Micrarchus)., Luke T Dunning, Alice B Dennis, Brent J Sinclair, Richard D Newcomb, Thomas R Buckley

Biology Publications

In widespread and genetically structured populations, temperature variation may lead to among-population differentiation of thermal biology. The New Zealand stick insect genus Micrarchus contains four species that inhabit different thermal environments, two of which are geographically widespread. RNA-Seq and quantitative PCR were used to investigate the transcriptional responses to cold shock among lowland and alpine species to identify cold-responsive transcripts that differ between the species and to determine whether there is intraspecific geographical variation in gene expression. We also used mitochondrial DNA, nuclear 28S ribosomal DNA and transcriptome-wide SNPs to determine phylogeographic structure and the potential for differences in genetic …


Obligate Male Death And Sexual Cannibalism In Dark Fishing Spiders, Steven Schwartz, William E. Wagner, Eileen A. Hebets Jun 2014

Obligate Male Death And Sexual Cannibalism In Dark Fishing Spiders, Steven Schwartz, William E. Wagner, Eileen A. Hebets

Eileen Hebets Publications

Male dark fishing spiders (Dolomedes tenebrosus Araneae, Pisauridae) always die during their first and only copulation, making all males monogynous. Such obligate male death can be adaptive if it facilitates sexual cannibalism, and if sexual cannibalism results in male reproductive benefits, such as an advantage in sperm competition through reduced female remating. We first conducted an experiment to determine the extent to which D. tenebrosus (1) males are cannibalized by females and (2) females engage in remating, both of which are prerequisites for several adaptive hypotheses of male self-sacrifice. We then conducted an experiment to test the hypothesis that …


The Neotropical Genus Austrolebias: An Emerging Model Of Annual Killifishes, Nibia Berois, María J. Arezo, Rafael O. De Sá Jun 2014

The Neotropical Genus Austrolebias: An Emerging Model Of Annual Killifishes, Nibia Berois, María J. Arezo, Rafael O. De Sá

Biology Faculty Publications

Annual fishes are found in both Africa and South America occupying ephemeral ponds that dried seasonally. Neotropical annual fishes are members of the family Rivulidae that consist of both annual and non-annual fishes. Annual species are characterized by a prolonged embryonic development and a relatively short adult life.

Males and females show striking sexual dimorphisms, complex courtship, and mating behaviors. The prolonged embryonic stage has several traits including embryos that are resistant to desiccation and undergo up to three reversible developmental arrests until hatching. These unique developmental adaptations are closely related to the annual fish life cycle and are the …


Privatization And Property In Biology, Joan E. Strassmann, David C. Queller Jun 2014

Privatization And Property In Biology, Joan E. Strassmann, David C. Queller

Biology Faculty Research

Organisms evolve to control, preserve, protect and invest in their own bodies. When they do likewise with external resources they privatize those resources and convert them into their own property. Property is a neglected topic in biology, although examples include territories, domiciles and nest structures, food caching, mate guarding, and the resources and partners in mutualisms. Property is important because it represents a solution to the tragedy of the commons; to the extent that an individual exerts long-term control of its property, it can use it prudently, and even invest in it. Resources most worth privatizing are often high in …


Photosynthetic Thermal Tolerance And Recovery To Short Duration Temperature Stress In Desert And Montane Plants: A Comparative Study, David William Gallagher Jun 2014

Photosynthetic Thermal Tolerance And Recovery To Short Duration Temperature Stress In Desert And Montane Plants: A Comparative Study, David William Gallagher

Master's Theses

  • Climate change models predict an increase in frequency and amplitude of extreme weather events, including heat waves. To better predict how the composition and distribution of plant assemblages might respond to these changes in temperature, it is important to understand how species currently respond to these extremes. Photosynthetic thermal tolerance (T25)and photosynthetic recovery (RT25) were quantified in 27 species. We also studied the relationships between T25, RT25 and leaf mass per area (LMA). Leaf temperature was also monitored in the field.
  • Leaves used in this study were collected from two distinct …


Insect Visitation Of Peduncular And Petiolar Extrafloral Nectar Glands On Castor Bean (Ricinus Communis L.) Plants In Southern California, Victor D. Carmona-Galindo, Taylor Waters, David Chirikian Jun 2014

Insect Visitation Of Peduncular And Petiolar Extrafloral Nectar Glands On Castor Bean (Ricinus Communis L.) Plants In Southern California, Victor D. Carmona-Galindo, Taylor Waters, David Chirikian

Biology Faculty Works

Castor bean (Ricinus communis L.) is a myrmecophytic plant species with specialized extrafloral nectar (EFN) glands that serve to attract predatory insects, which in return defend plant-tissues against herbivores. The EFN glands on castor bean plants are located along the leaf petioles as well as on the peduncles of its imperfect (unisexual) flowers. This field-project evaluates the richness, diversity, and species assemblage of insects visiting EFN glands located on (female and male) flower peduncles and leaf petioles on castor bean plants growing in a Southern California coastal landscape. We detected that EFN glands on female-flower peduncles were visited by …


Temporal Variations In The Abundance And Composition Of Biofilm Communities Colonizing Drinking Water Distribution Pipes, John J. Kelly, Nicole Minalt, Alessandro Culotti, Marsha Pryor, Aaron Packman May 2014

Temporal Variations In The Abundance And Composition Of Biofilm Communities Colonizing Drinking Water Distribution Pipes, John J. Kelly, Nicole Minalt, Alessandro Culotti, Marsha Pryor, Aaron Packman

Biology: Faculty Publications and Other Works

Pipes that transport drinking water through municipal drinking water distribution systems (DWDS) are challenging habitats for microorganisms. Distribution networks are dark, oligotrophic and contain disinfectants; yet microbes frequently form biofilms attached to interior surfaces of DWDS pipes. Relatively little is known about the species composition and ecology of these biofilms due to challenges associated with sample acquisition from actual DWDS. We report the analysis of biofilms from five pipe samples collected from the same region of a DWDS in Florida, USA, over an 18 month period between February 2011 and August 2012. The bacterial abundance and composition of biofilm communities …


Joint Phenotypes, Evolutionary Conflict And The Fundamental Theorem Of Natural Selection, David C. Queller May 2014

Joint Phenotypes, Evolutionary Conflict And The Fundamental Theorem Of Natural Selection, David C. Queller

Biology Faculty Research

Multiple organisms can sometimes affect a common phenotype. For example, the portion of a leaf eaten by an insect is a joint phenotype of the plant and insect and the amount of food obtained by an offspring can be a joint trait with its mother. Here, I describe the evolution of joint phenotypes in quantitative genetic terms. A joint phenotype for multiple species evolves as the sum of additive genetic variances in each species, weighted by the selection on each species. Selective conflict between the interactants occurs when selection takes opposite signs on the joint phenotype. The mean fitness of …


Use Of Coastal Islands By Seabirds: A Tool To Guide Future Marine Protected Areas In California, Dana A. Page May 2014

Use Of Coastal Islands By Seabirds: A Tool To Guide Future Marine Protected Areas In California, Dana A. Page

Master's Projects and Capstones

Seabird breeding colonies on islands off the coast of California offer a unique tool to help guide marine spatial planning. The life histories of seabirds can be used to develop locations of ecological importance along the coast of California. Tracking methodologies and habitat modeling related to seabird habitat utilization can be used to inform management approaches which can aid in the expansion of marine protected areas (MPAs). Protecting ocean habitats will help mitigate impacts of climate change and ensure the ecosystem services provided by marine environments. Areas within the Monterey Bay National Marine Sanctuary were analyzed to locate candidate MPA …


Water Water Everywhere: Analyzing Long Island's Water Issues And Finding Solutions For A Sustainable Future, Anthony T. Becker May 2014

Water Water Everywhere: Analyzing Long Island's Water Issues And Finding Solutions For A Sustainable Future, Anthony T. Becker

2014 Student Theses

Over three million people call Long Island their home. With access to beautiful landscapes, world-renowned beaches, and proximity to New York City, it is no wonder that so many proudly call this geographic stretch of glacial till their home. However, throughout the years our actions do not necessarily reflect this affection we have to our home. Years of sprawl and human infestation across the island have resulted in widespread environmental degradation. Specifically, the water we drink and the beaches we enjoy have become endangered. I plan on studying the urban ecology of how intensified population growth led to the eutrophication …


Level Of Uv-B Radiation Influences The Effects Of Glyphosate-Based Herbicide On Fitness Of The Spotted Salamander, Nicholas A. Levis May 2014

Level Of Uv-B Radiation Influences The Effects Of Glyphosate-Based Herbicide On Fitness Of The Spotted Salamander, Nicholas A. Levis

Masters Theses & Specialist Projects

Numerous causes have been implicated in contributing to amphibian population declines since the 1980's, with habitat modification, ultraviolet radiation (UV-B) and environmental contaminants (such as glyphosate-based herbicide) being among the most common. This study identifies the effects of a generic glyphosate-based herbicide (GLY- 4 Plus) on mortality, immune function, body condition, and morphological plasticity of larvae of the spotted salamander (Ambystoma maculatum) under conditions that reflect open and closed canopy light regimes. Larval salamander responses to glyphosate-based herbicide varied depending on UV-B conditions. In general, it appears that an open canopy (i.e. greater UV-B exposure) may confer fitness benefits. In …


Wire Netting Reduces African Elephant (Loxodonta Africana) Impact To Selected Large Trees In South Africa, Kelly Derham May 2014

Wire Netting Reduces African Elephant (Loxodonta Africana) Impact To Selected Large Trees In South Africa, Kelly Derham

Masters Theses & Specialist Projects

African elephants (Loxodonta africana) are ecosystem engineers in that they substantially alter the environment through their unique foraging and feeding habits. At high densities, elephants potentially have negative impacts on the environment, specifically to large trees. Because of this, recent increases of elephants in the Associated Private Nature Reserves (APNR) on the Western Boundary of Kruger National Park, South Africa have caused concern regarding the health of several species of tree. My objective was to assess the effectiveness of wrapping protective wire netting around the trunk of the tree in preventing and reducing bark stripping by elephants. 2,668 …


Tactical Adjustment Of Signaling Leads To Increased Mating Success And Survival, Laura Sullivan-Beckers, Eileen A. Hebets May 2014

Tactical Adjustment Of Signaling Leads To Increased Mating Success And Survival, Laura Sullivan-Beckers, Eileen A. Hebets

Eileen Hebets Publications

Most sexually reproducing animals overcome the challenge of searching for and attracting mates by utilizing signals that are broadcast through a spatially and temporally varying environment. A diverse suite of behavioral solutions exist for overcoming such environmental variability, including the adjustment of signaling behavior based upon receiver feedback. Few studies have directly examined the relationship between such tactical signaling adjustments and proxies of male fitness; the few that have, failed to find a relationship. Using the wolf spider, Schizocosa rovneri, we set out to first quantify among-male variation in the form and degree of responsiveness to female feedback. Following …


Influence Of Wildfire Disturbance And Post-Fire Seeding On Vegetation And Insects In Sagebrush Habitats, Ashley T. Rohde May 2014

Influence Of Wildfire Disturbance And Post-Fire Seeding On Vegetation And Insects In Sagebrush Habitats, Ashley T. Rohde

Boise State University Theses and Dissertations

Disturbance events alter community composition and structure because of differences in resistance and resilience of individual taxa, changes in habitat resulting in colonization by new taxa and alteration of biotic interaction patterns. Recent changes in disturbance types, frequencies and intensities caused by anthropogenic activities may further alter community composition and structure if these disturbances exceed the tolerances or adaptations of some taxa. In sagebrush steppe habitats of the western United States, wildfire is the current dominant disturbance type, burning millions of hectares annually. Further, up to 90% of sagebrush-steppe ecosystems are affected by anthropogenic influences such as invasive species. Post-fire …


Paleozoic Seed Bank And Their Ecological Significance, Petra Seka Yehnjong May 2014

Paleozoic Seed Bank And Their Ecological Significance, Petra Seka Yehnjong

Electronic Theses and Dissertations

Soil seed banks are a reservoir of viable seeds present in the soil in plant communities. They have been studied and characterized in various ways in different habitats. However, these studies are limited to modern seed banks. This study extends seed bank studies to the Paleozoic Era. It was hypothesized that size distribution and seed density in Paleozoic seed banks exhibit similar patterns as in modern seed banks. Seed sizes and seed density of fossil seed from Wise Virginia were estimated. Modern seed bank information was obtained from published data. Data were analyzed using one-way ANOVA and Kruskal-Wallis test. The …


Population Genetics And Microbial Communities Of The Gopher Tortoise (Gopherus Polyphemus), Daniel Lyle Gaillard May 2014

Population Genetics And Microbial Communities Of The Gopher Tortoise (Gopherus Polyphemus), Daniel Lyle Gaillard

Dissertations

The gopher tortoise, Gopherus polyphemus, is an endangered species living in the southeastern United States. The recent and drastic decline in tortoise numbers has resulted in a multi-faceted approach to conserve this species. I used a population genetic approach to determine the population structure, genetic diversity and barriers to gene flow at a broad, regional and local scale. Tortoises are divided into five distinct genetic populations at the broad scale, the central populations have the highest levels of genetic diversity and the Tombigbee, Mobile, Apalachicola, Suwannee and St. John’s Rivers appear to be barriers to gene flow. At the regional …


The Delivery, Speciation, And Fate Of Trace Elements In St. Louis Bay, Mississippi, Gopal Bera May 2014

The Delivery, Speciation, And Fate Of Trace Elements In St. Louis Bay, Mississippi, Gopal Bera

Dissertations

Estuaries are dynamic regions in which there can be significant modification of the riverine flux of trace elements to the open ocean due to various geochemical, physical, and biological processes. Additionally, estuaries are often subject to anthropogenic inputs of trace elements. The first portion of this study investigated the source, behavior, and sediment interaction of anthropogenic stable cesium (Cs) in St. Louis Bay (SLB), MS. A consistent increase in stable Cs concentration was noticed in sediment cores starting from a period when a titanium dioxide refinery on SLB started operations. Weak correlation between Cs and clay percentage and strong correlations …


Plasticity In Female Mate Choosiness: A Result Of Variation In Perceived Predation Risk And The Interaction Of Female Age And Male Density, Ashley N. Atwell May 2014

Plasticity In Female Mate Choosiness: A Result Of Variation In Perceived Predation Risk And The Interaction Of Female Age And Male Density, Ashley N. Atwell

School of Biological Sciences: Dissertations, Theses, and Student Research

In many species, female mate choices can be a strong source of sexual selection. Females often prefer a certain male phenotype, and this can be due to benefits females gain from mating with preferred males. However, such benefits can sometimes be outweighed by the cost of searching for a preferred male. These costs and benefits often change concomitantly with changes in environmental (e.g., predator abundance and conspecific density) and internal factors (e.g., female age). Thus, female mate choosiness (the degree to which preferences for certain males are expressed) should often be plastic. Plasticity in female mate choosiness may be complicated …


Ecomorphological And Genetic Investigations Into The Utah Lake, Ut Sucker Complex With Comparisons To The Jackson Lake, Wy Sucker Complex, David D. Cole May 2014

Ecomorphological And Genetic Investigations Into The Utah Lake, Ut Sucker Complex With Comparisons To The Jackson Lake, Wy Sucker Complex, David D. Cole

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Natural selection within the sucker family of fishes has produced populations including typical benthic (bottom-feeding) suckers (Catostomus) and lakesuckers (Chasmistes), mid-water plankton eaters, in several large western North American lakes. Suckers of intermediate morphology (shape) exist in a continuum of head, mouth, and body characteristics between these two extremes. All current lakesuckers are listed Endangered, and population declines have been attributed in part to hybridization with their Catostomus neighbors.

Chapter 2 describes the investigation of the relationship between morphology and genetics of June sucker, a lakesucker, and Utah sucker, a benthic sucker, in Utah Lake, Utah. …


The Role Of Vegetation Structure, Composition, And Nutrition In Greater Sage-Grouse Ecology In Northwestern Utah, Brian R. Wing May 2014

The Role Of Vegetation Structure, Composition, And Nutrition In Greater Sage-Grouse Ecology In Northwestern Utah, Brian R. Wing

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The greater sage-grouse (Centrocercus urophasianus; sage-grouse) is the largest grouse species in North America and an indicator species for the condition of sagebrush (Artemisia spp.) ecosystems. The Box Elder Sage-Grouse Management Area (SGMA) in northwestern Utah encompasses one of the state’s largest sage-grouse populations.

To fill knowledge gaps regarding the population inhabiting the Raft River subunit of the Box Elder SGMA, I captured, radio-marked, and monitored 123 (68 female, 55 male) sage-grouse from January 2012 through December 2013. My purpose was to describe how the seasonal movements, survival, and reproductive rates of this sage-grouse population …


Survival, Abundance, And Geographic Distribution Of Temperate-Nesting Canada Geese (Branta Canadensis) In Arkansas, Margaret Eliese Ronke May 2014

Survival, Abundance, And Geographic Distribution Of Temperate-Nesting Canada Geese (Branta Canadensis) In Arkansas, Margaret Eliese Ronke

Graduate Theses and Dissertations

Temperate-nesting Canada geese in Arkansas have grown in abundance and range since reintroduction in the 1980s. The Arkansas Game and Fish Commission uses harvest and other methods to maintain the population at desired levels. However, continued management of temperate-nesting geese requires knowledge of the population's demographics and current range to help establish quantifiable management goals.

To assess the need and effect of changing hunting regulations, survival and recovery rates and abundance were estimated for this population. Annual survival rates of temperate-nesting Canada geese banded and recovered in Arkansas from 2005 to 2011 were estimated using the Burnham joint live-dead recovery …


Adaptive Strategies For Foraging And Their Implications For Flower Constancy, Or: Do Honey Bees Multitask?, Ashley E. Wagner May 2014

Adaptive Strategies For Foraging And Their Implications For Flower Constancy, Or: Do Honey Bees Multitask?, Ashley E. Wagner

Electronic Theses and Dissertations

Classical experiments on honey bee time-memory showed that foragers trained to collect food at a fixed time of day return the following day with remarkable time-accuracy. Previous field experiments revealed that not all foragers return to a food source on unrewarded test days. Rather, there exist 2 subgroups: “persistent” foragers reconnoiter the source; “reticent” foragers wait in the hive for confirmation of source availability. To examine how these foragers contribute to a colony’s ability to reallocate foragers across sources with rapidly changing availabilities, foragers were trained to collect sucrose during a restricted window for several days and observed over 3 …


Sink Or Ecological Trap For Tree Swallows In Central Minnesota?, James T. Pathoulas, Nicole E. Noyes Apr 2014

Sink Or Ecological Trap For Tree Swallows In Central Minnesota?, James T. Pathoulas, Nicole E. Noyes

Celebrating Scholarship & Creativity Day (2011-2017)

Background: An ecological trap is typically defined as a low-quality habitat, incapable of sustaining a population, which is preferred over a high quality habitat. Ecological traps may lead to species extinction in populations with 1) strict habitat requirements 2) minimal information about the habitat, and 3) low population size. Tree Swallows (Tachycineta bicolor) meet the former two of these criteria.

Methods: We monitored Tree Swallow (TS) nest boxes (n=90) at two ecologically similar sites A and B with similar occupancy rates. Site B has lower reproductive fitness —suggestive of an ecological trap. Binary logistic regression was used to …


Fifth Specimen Of The Nine-Banded Armadillo (Dasypus Novemcinctus) From Nebraska, Keith Geluso, Greg D. Wright, Angelina E. Wright Apr 2014

Fifth Specimen Of The Nine-Banded Armadillo (Dasypus Novemcinctus) From Nebraska, Keith Geluso, Greg D. Wright, Angelina E. Wright

Transactions of the Nebraska Academy of Sciences and Affiliated Societies

The nine-banded armadillo (Dasypus novemcinctus) has moved northward in the Great Plains in the last century, reaching distributional limits in Nebraska for pioneering individuals. Herein, we report on the fifth specimen from Nebraska. A male individual was obtained from Lincoln County representing a new county record for Nebraska and one of the northwestern-most specimens in the United States.


Host-Parasite Interactions In An Invasive Songbird, Courtney A.C. Coon Apr 2014

Host-Parasite Interactions In An Invasive Songbird, Courtney A.C. Coon

USF Tampa Graduate Theses and Dissertations

Introduced species are the greatest threat to biodiversity after habitat loss. Understanding the processes that permit organisms to become successful invaders may provide opportunities to prevent or limit their dispersal and establishment and thereby alleviate some of their harmful effects. The goal of my dissertation research has been to investigate whether invasive species have distinctive interactions with parasites, and some of the mechanisms that may underlie that variation. I used one of the world's most successful vertebrate invaders as a case study: the house sparrow (Passer domesticus; Introduction).

Previous research in the house sparrow suggested that loss of …


An Investigation Into The Habitat, Behavior And Opportunistic Feeding Strategies Of The Protected Goliath Grouper (Epinephelus Itajara), Angela Collins Apr 2014

An Investigation Into The Habitat, Behavior And Opportunistic Feeding Strategies Of The Protected Goliath Grouper (Epinephelus Itajara), Angela Collins

USF Tampa Graduate Theses and Dissertations

Groupers (Epinephelidae: Epinephelinae) are apex predators within many reef communities worldwide. Grouper landings contribute significantly to global fisheries, and many populations are suffering from unsustainable levels of exploitation. The large size, site specificity and catchability of most groupers increase susceptibility to fishing pressure, and a large number of grouper species throughout the world are currently overfished. Multiple species are listed as endangered or threatened, and many have suffered local extirpations across their range. Removal of these upper level predators can significantly alter community structure and result in second order effects that may have critical ecological implications. The economic and ecological …


Sex Ratio Bias And Extinction Risk In An Isolated Population Of Tuatara (Sphenodon Punctatus), Kristine L. Grayson, Nicola J. Mitchell, Joanne M. Monks, Susan N. Keall, Joanna N. Wilson, Nicola J. Nelson Apr 2014

Sex Ratio Bias And Extinction Risk In An Isolated Population Of Tuatara (Sphenodon Punctatus), Kristine L. Grayson, Nicola J. Mitchell, Joanne M. Monks, Susan N. Keall, Joanna N. Wilson, Nicola J. Nelson

Biology Faculty Publications

Understanding the mechanisms underlying population declines is critical for preventing the extinction of endangered populations. Positive feedbacks can hasten the process of collapse and create an ‘extinction vortex,’ particularly in small, isolated populations. We provide a case study of a male-biased sex ratio creating the conditions for extinction in a natural population of tuatara (Sphenodon punctatus) on North Brother Island in the Cook Strait of New Zealand. We combine data from long term mark-recapture surveys, updated model estimates of hatchling sex ratio, and population viability modeling to measure the impacts of sex ratio skew. Results from the mark-recapture …


The Effects Of Invasive Macrophytes Phragmites Australis And Typha Angustifolia On Nitrate Removal In High Nitrate Wetland Sediments, Lauren Mackenzie Beal Apr 2014

The Effects Of Invasive Macrophytes Phragmites Australis And Typha Angustifolia On Nitrate Removal In High Nitrate Wetland Sediments, Lauren Mackenzie Beal

Theses and Dissertations

Constructed wetlands are quickly becoming inundated with invasive species like Phragmites australis and Typha angustifolia which are capable of changing whole ecosystem function and community composition. We wanted to assess how plants affect dissolved oxygen (DO) and dissolved organic carbon concentrations (DOC), and in turn if they increase nitrate (NO3-N) removal rates relative to barren sediments. Using a NO3-N/Br tracer test, we tested NO3-N removal rates, DO, and DOC concentrations. After the tracer test, we measured above- and below-ground plant biomass and sediment characteristics. NO3-N removal did not differ across the treatments. Phragmites australis microcosms had significantly higher sediment bulk …