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Ecology and Evolutionary Biology

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Full-Text Articles in Life Sciences

Isotopic Discrimination In The Double-Crested Cormorant (Phalacrocorax Auritus), Elizabeth C. Craig, Brian S. Dorr, Katie C. Hanson-Dorr, Jed P. Sparks, Paul D. Curtis Oct 2015

Isotopic Discrimination In The Double-Crested Cormorant (Phalacrocorax Auritus), Elizabeth C. Craig, Brian S. Dorr, Katie C. Hanson-Dorr, Jed P. Sparks, Paul D. Curtis

Brian S Dorr

The diet-tissue discrimination factor is the amount by which a consumer’s tissue varies isotopically from its diet, and is therefore a key element in models that use stable isotopes to estimate diet composition. In this study we measured discrimination factors in blood (whole blood, red blood cells and plasma), liver, muscle and feathers of Double- crested Cormorants (Phalacrocorax auritus) for stable isotope ratios of carbon, nitrogen and sulfur. Cormorants exhibited discrimination factors that differed significantly among tissue types (for carbon and nitrogen), and differed substantially (in the context of the isotopic variation among relevant prey species) from those observed ...


Rooted In Hell: Simulating Phragmites Australis, Rachel Nydegger Rozum, Jacob Duncan, James Powell Ph.D. Jul 2015

Rooted In Hell: Simulating Phragmites Australis, Rachel Nydegger Rozum, Jacob Duncan, James Powell Ph.D.

Rachel Nydegger Rozum

Across the estuaries of the east coast and wetlands of the Great Lakes, the invasive grass Phragmites australis outcompetes other vegetation and destroys local ecosystems. Because its roots are tolerant to salinity that other plants find hellish, Phragmites invasions begin with vegetative spread of genetic clones in brackish marshlands.This plant can grow over three meters tall at densities of 50 stems/m2, provides poor wildlife habitat, and is very difficult to eradicate. A discrete life stage model on a yearly time step captures seed survivorship in a seed bank, sexual and asexual recruitment into a juvenile age class, and ...


Influence Of Simulated Double-Crested Cormorant, Phalacrocorax Auritus, Predation On Multiple-Batch Production Of Channel Catfish, Ictalurus Punctatus, Brian S. Dorr, Carole R. Engle Jun 2015

Influence Of Simulated Double-Crested Cormorant, Phalacrocorax Auritus, Predation On Multiple-Batch Production Of Channel Catfish, Ictalurus Punctatus, Brian S. Dorr, Carole R. Engle

Brian S Dorr

The double-crested cormorant, Phalacrocorax auritus, is considered the primary depredating bird species on commercially produced channel catfish, Ictalurus punctatus, in the southeastern USA. We simulated different levels of cormorant predation on losses at harvest and economic effects on channel catfish production in a multiple-batch cropping system. We observed significant (P<0.05) declines in catfish production at increasing levels of cormorant predation in this study. This decline was mitigated by increased individual growth of catfish at higher predation rates (i.e., lower catfish densities). This mitigating effect produced a non-linear relationship with total kg of catfish harvested per pond resulting in a non-linear incremental increase in breakeven price related to predation. Costs of production ($/kg) increased with increasing predation levels up to very high levels of predation with a cumulative maximum increase in breakeven price of $0.143/kg. These results indicate that losses at harvest due to cormorant predation occur immediately but are mitigated in part by compensatory growth of individual catfish. Losses due to cormorant predation in multi-batch systems can be considerable, but there is not a 1:1 relationship between losses and kg of catfish harvested due to compensatory actors.


Impacts Of Colonial Waterbirds On Vegetation And Potential Restoration Of Island Habitats, Christopher R. Ayers, Katie C. Hanson-Dorr, Sadie O'Dell, Charles D. Lovell, Michael L. Jones, Jason R. Suckow, Brian S. Dorr May 2015

Impacts Of Colonial Waterbirds On Vegetation And Potential Restoration Of Island Habitats, Christopher R. Ayers, Katie C. Hanson-Dorr, Sadie O'Dell, Charles D. Lovell, Michael L. Jones, Jason R. Suckow, Brian S. Dorr

Brian S Dorr

Colonial waterbirds have impacted forested island ecosystems throughout their breeding range, changing vegetation, and soil characteristics and bird communities.Our objectives were to (1) determine effects of three levels of colonial waterbird exclusion on overall vegetation diversity and growth, and survival of a candidate restoration species (black elderberry; Sambucus nigra canadensis); (2) investigate effects of different planting techniques on survival and growth of black elderberry; and (3) determine effects of waterbird colonization on soil chemistry. In 2012, we investigated effects of three levels of waterbird exclusion (none control plots [CON]; partial, which excluded waterbirds larger than gulls [PEX]; and full ...


Slotted Drainage Pipe For Sub-Irrigation, David A. Bainbridge Jan 2015

Slotted Drainage Pipe For Sub-Irrigation, David A. Bainbridge

David A Bainbridge

Subirrigation with drainage pipe was effective for planting a windbreak in the Mojave Desert. The pipe was refilled periodically with a water truck. Survival was very good.


Preliminary Home Range Study Of Juvenile Chinese Horseshoe Crabs, Tachypleus Tridentatus (Xiphosura), Using Passive Tracking Methods, Kit Yue Kwan, Pks Shin, Sg Cheung Jan 2015

Preliminary Home Range Study Of Juvenile Chinese Horseshoe Crabs, Tachypleus Tridentatus (Xiphosura), Using Passive Tracking Methods, Kit Yue Kwan, Pks Shin, Sg Cheung

KWAN Kit Yue, Billy

Three passive tracking methods, using colored plastic tag (CPT), passive integrated transponder (PIT) tag, and CPT plus PIT were compared to track the movements of juvenile Chinese horseshoe crabs, Tachypleus tridentatus, in summer 2013 on a mudflat in Hong Kong. The study site was re-visited within 2 months after the release of the tagged individuals on ten occasions during low tides. The cumulative recovery rates of the tagged juveniles ranged from 70 to 82 %, with the number of position fixes where each individual was recovered during the repeated field visits varying from one to seven. Based on the adaptive kernel ...


Social Sciences, Not Given Dec 2014

Social Sciences, Not Given

cm articles

No abstract provided.


Wintering Ecology Of Adult North American Ospreys, Brian E. Washburn, Charles J. Henny, Mark S. Martell, Richard O. Bierregaard, Brian S. Dorr, Thomas J. Olexa Dec 2014

Wintering Ecology Of Adult North American Ospreys, Brian E. Washburn, Charles J. Henny, Mark S. Martell, Richard O. Bierregaard, Brian S. Dorr, Thomas J. Olexa

Brian S Dorr

North American Ospreys (Pandion haliaetus) typically migrate long distances to their wintering grounds in the tropics. Beyond the general distribution of their wintering range (i.e., the Caribbean, South America, and Central America), very little is known about the wintering ecology of these birds. We used satellite telemetry to determine the duration of wintering period, to examine the characteristics of wintering areas used by Ospreys, and to quantify space use and activity patterns of wintering Ospreys. Adult Ospreys migrated to wintering sites and exhibited high wintering site fidelity among years. Overall, Ospreys wintered on river systems (50.6%) more than ...


Geographic Segregation And Evidence Of Density-Dependent Changes In Sex Ratios In An Abundant Colonial Waterbird, Brian S. Dorr, Katie C. Hanson-Dorr, Travis L. Devault, Alban Guillaumet, Scott C. Barras Dec 2014

Geographic Segregation And Evidence Of Density-Dependent Changes In Sex Ratios In An Abundant Colonial Waterbird, Brian S. Dorr, Katie C. Hanson-Dorr, Travis L. Devault, Alban Guillaumet, Scott C. Barras

Brian S Dorr

Demographic information, such as geographic segregation of sexes and sex ratio data, is needed to develop, model and evaluate conservation and management strategies for wildlife. A variety of physiological, behavioral and environmental factors can influence segregation of sexes and sex ratios, many of which originate with density- dependent processes. Departure from 50:50 sex ratios of double-crested cormorants (Phalacrocorax auritus) collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z-test as well as Stouffer’s weighted Z-tests. In addition, a specifically-designed randomization test was used to evaluate density-dependent ...


Freshwater Habitats And Fishing Activities In The Buriganga River, Dhaka, Bangladesh., Md.Muzammel Hossain, Mohammad Abdul Baki Nov 2014

Freshwater Habitats And Fishing Activities In The Buriganga River, Dhaka, Bangladesh., Md.Muzammel Hossain, Mohammad Abdul Baki

Md.Muzammel Hossain

The Buriganga River has served as the central artery to economic life in Dhaka city for centuries. But Buriganga River is the most polluted river in Bangladesh. During the study period (December 2012 to November 2013), we directly observed freshwater habitats and fishing activities by boat-base survey from china-Bangladesh Friendship Bridge (90°26´12'' E and 23°40´25''N) to Amin bazar Bridge (90°20´12''E and 23°46´25''N) in the Buriganga River. Freshwater habitats were observed at babu bazar, kamrangichar, kholamora ghat and shadar ghat throughout the year in the River. Different types of fishes ...


Mitigation Site Soil Characteristics And The Effects Of Inoculation, Nursery Fertilizer Practices And Irrigation On Survival And Growth Of Mesquite (Prosopis Glandulosa) In The Coachella Valley, California, David A. Bainbridge, Marcelle M. Darby Jul 2014

Mitigation Site Soil Characteristics And The Effects Of Inoculation, Nursery Fertilizer Practices And Irrigation On Survival And Growth Of Mesquite (Prosopis Glandulosa) In The Coachella Valley, California, David A. Bainbridge, Marcelle M. Darby

David A Bainbridge

Prosopis glandulosa var. torreyana (mesquite, honey mesquite) is a small to medium sized leguminous tree that was once common in the low desert of California. Widespread destruction of mesquite woodlands in the Coachella Valley of southern California for fuel wood, agricultural and urban development, and urbanization has reduced once vast stands to isolated remnants. The rerouting and widening of Highway 86 in the Coachella Valley was a typical example of ongoing mesquite woodland removal. Despite the recognized need for mitigation, relatively little information on mesquite establishment in California is available. This research explored mesquite establishment by replanting on an abandoned ...


Effects Of Prey Abundance On Breeding Season Diet Of Northern Goshawks (Accipiter Gentilis) Within An Unusual Prey Landscape, Robert A. Miller, Jay D. Carlisle, Marc J. Bechard Mar 2014

Effects Of Prey Abundance On Breeding Season Diet Of Northern Goshawks (Accipiter Gentilis) Within An Unusual Prey Landscape, Robert A. Miller, Jay D. Carlisle, Marc J. Bechard

Robert Miller

A critical element of diet analysis is species adaptability to alternative prey sources. The breeding season diet of Northern Goshawks (Accipiter gentilis) includes both mammalian and avian species, varies geographically, and is often dependent upon tree squirrels of the genera Sciurus and Tamiasciurus>/i>. We studied alternative prey sources of Northern Goshawks in the South Hills of south-central Idaho, an area where tree squirrels are naturally absent and other prey frequently important in the diet of goshawks, such as smaller corvids, are uncommon. We quantified the diet of goshawks using nest cameras and surveyed abundance of prey using line transects ...


Avian Influenza Virus Prevalence In Migratory Waterfowl In The United States, 2007-2009, Scott R. Groepper Mr., Thomas Deliberto, Mark Vrtiska, Kerri Pedersen, Seth Swafford, Scott Hyngstrom Jan 2014

Avian Influenza Virus Prevalence In Migratory Waterfowl In The United States, 2007-2009, Scott R. Groepper Mr., Thomas Deliberto, Mark Vrtiska, Kerri Pedersen, Seth Swafford, Scott Hyngstrom

Scott R Groepper

SUMMARY. We analyzed 155,535 samples collected for surveillance of avian influenza viruses (AIVs), in the United States from 2007 to 2009, from migratory waterfowl (ducks, geese, and swans). The goal was to elucidate patterns of prevalence by flyway and functional groups to determine targets for future surveillance. Apparent prevalence of AIV was highest in the Pacific Flyway in 2007–2008 (14.2% and 14.1%, respectively), in the Mississippi Flyway in 2009 (16.8%), and lowest each year in the Atlantic Flyway (range, 7.3%–8.9%). Dabbling ducks had higher apparent prevalence of AIV (12.8%–18.8 ...


Recreating Mesquite Mounds (Nebkas) In The Colorado Desert, David A. Bainbridge Jan 2014

Recreating Mesquite Mounds (Nebkas) In The Colorado Desert, David A. Bainbridge

David A Bainbridge

Accretion dunes or mounds (also known as nebkas or nebkhas) are formed when plants capture and then are partially buried in wind-blown sand. In the San Felipe drainage in the western Colorado Desert, mesquite (Prosopis glandulosa Torrey var. torreyana (L. D. Benson) M. C. Johnston)) forms dunes up to 5 m high. These are ecologically important for both ecosystem structure (primarily habitat) and function (soil accumulation, moisture retention and nutrient cycling). The widening of California state highway 86 damaged and removed several mesquite mounds and the California Department of Transportation asked us to explore techniques for recreating them to reduce ...


Resolution Of Deep Nodes Yields An Improved Backbone Phylogeny And A New Basal Lineage To Study Early Evolution Of Asteraceae, Jose L. Panero, Susana E. Freire, Luis Ariza Espinar, Bonnie S. Crozier, Gloria E. Barboza, Juan J. Cantero Jan 2014

Resolution Of Deep Nodes Yields An Improved Backbone Phylogeny And A New Basal Lineage To Study Early Evolution Of Asteraceae, Jose L. Panero, Susana E. Freire, Luis Ariza Espinar, Bonnie S. Crozier, Gloria E. Barboza, Juan J. Cantero

Jose L. Panero

A backbone phylogeny that fully resolves all subfamily and deeper nodes of Asteraceae was constructed using 14 chloroplast DNA loci. The recently named genus Famatinanthus was found to be sister to the Mutisioideae–Asteroideae clade that represents more than 99% of Asteraceae and was found to have the two chloroplast inversions present in all Asteraceae except the nine genera of Barnadesioideae. A monotypic subfamily Famatinanthoideae and tribe Famatinantheae are named herein as new. Relation- ships among the basal lineages of the family were resolved with strong support in the Bayesian analysis as (Barnadesioideae (Famatinanthoideae (Mutisioideae (Stifftioideae (Wunderlichioideae– Asteroideae))))). Ancestral state ...


Architecture Of Ponderosa Pine Bark In Relation To Spalling Behavior, Eric R. Force Jan 2014

Architecture Of Ponderosa Pine Bark In Relation To Spalling Behavior, Eric R. Force

Eric R Force

Shedding/spalling behavior of ponderosa bark, with or without fire impetus, is primarily a function of the geometry of individual bark pieces, which are stable laterally due to their digitate shapes, and metastable radially due to flanges around the base of each piece. In detail, each piece is a zoned envelope of distinctive elements, separated from other pieces by another element. Different physical properties of these elements are probably involved in bark-piece expulsion, which requires sequential flange release. Criteria to determine any role of fire in bark-piece expulsion are described.


The Cumulative Effects Of Management On The Population Dynamics Of The Double-Crested Cormorant Phalacrocorax Auritus In The Great Lakes, Alban Guillaumet, Brian S. Dorr, Guiming Wang, Terry J. Doyle Jan 2014

The Cumulative Effects Of Management On The Population Dynamics Of The Double-Crested Cormorant Phalacrocorax Auritus In The Great Lakes, Alban Guillaumet, Brian S. Dorr, Guiming Wang, Terry J. Doyle

Brian S Dorr

Wildlife species have been subject to control efforts throughout human history due to real or alleged human–wildlife conflicts. The Double-crested Cormorant Phalacrocorax auritus in the interior of North America is no exception, with recent population growth leading to increased conflicts and consequently the development of many control programmes. These control programmes are usually conducted at local scales, often with little or no effort to assess their cumulative effects at the population level. We attempted the first comprehensive assessment of the cumulative effects of control at various spatio-temporal scales, focusing on 199 colonies of Double-crested Cormorant monitored during a 29-year ...


Effects Of Disturbance And Climate Change On Ecosystem Performance In The Yukon River Basin Boreal Forest, Bruce K. Wylie, Matthew Rigge, Brian Brisco, Kevin Murnaghan, Jennifer A. Rover Jan 2014

Effects Of Disturbance And Climate Change On Ecosystem Performance In The Yukon River Basin Boreal Forest, Bruce K. Wylie, Matthew Rigge, Brian Brisco, Kevin Murnaghan, Jennifer A. Rover

Bruce K. Wylie

A warming climate influences boreal forest productivity, dynamics, and disturbance regimes. We used ecosystem models and 250 m satellite Normalized Difference Vegetation Index (NDVI) data averaged over the growing season (GSN) to model current, and estimate future, ecosystem performance. We modeled Expected Ecosystem Performance (EEP), or anticipated productivity, in undisturbed stands over the 2000–2008 period from a variety of abiotic data sources, using a rule-based piecewise regression tree. The EEP model was applied to a future climate ensemble A1B projection to quantify expected changes to mature boreal forest performance. Ecosystem Performance Anomalies (EPA), were identified as the residuals of ...


Water Stress Strengthens Mutualism Among Ants, Trees, And Scale Insects, Elizabeth G. Pringle, Erol Akc¸Ay, Ted K. Raab, Rodolfo Dirzo, Deborah M. Gordon Nov 2013

Water Stress Strengthens Mutualism Among Ants, Trees, And Scale Insects, Elizabeth G. Pringle, Erol Akc¸Ay, Ted K. Raab, Rodolfo Dirzo, Deborah M. Gordon

Ted K. Raab

Abiotic environmental variables strongly affect the outcomes of species interactions. For example, mutualistic interactions between species are often stronger when resources are limited. The effect might be indirect: water stress on plants can lead to carbon stress, which could alter carbon-mediated plant mutualisms. In mutualistic ant–plant symbioses, plants host ant colonies that defend them against herbivores. Here we show that the partners’ investments in a widespread ant–plant symbiosis increase with water stress across 26 sites along a Mesoamerican precipitation gradient. At lower precipitation levels, Cordia alliodora trees invest more carbon in Azteca ants via phloem-feeding scale insects that ...


The Contribution Of Fe (Iii) And Humic Acid Reduction To Ecosystem Respiration In Drained Thaw Lake Basins Of The Arctic Coastal Plain, David A. Lipson, Ted K. Raab, Dominic Goria, Jaime Zlamal May 2013

The Contribution Of Fe (Iii) And Humic Acid Reduction To Ecosystem Respiration In Drained Thaw Lake Basins Of The Arctic Coastal Plain, David A. Lipson, Ted K. Raab, Dominic Goria, Jaime Zlamal

Ted K. Raab

Previous research showed that anaerobic respiration using iron (Fe) oxides as terminal electron acceptor contributed substantially to ecosystem respiration (ER) in a drained thaw lake basin (DTLB) on the Arctic coastal plain. As DTLB age, the surface organic layer thickens, progressively burying the Fe-rich mineral layers. We therefore hypothesized that Fe (III) availability and Fe reduction would decline with basin age. We studied four DTLB across an age gradient, comparing seasonal changes in the oxidation state of dissolved and extractable Fe pools and the estimated contribution of Fe reduction to ER. The organic layer thickness did not strictly increase with ...


Metagenomic Insights Into Anaerobic Metabolism Along An Arctic Peat Soil Profile, David A. Lipson, John M. Haggerty, Archana Srinivas, Ted K. Raab, Shashank Sathe, Elizabeth A. Dinsdale May 2013

Metagenomic Insights Into Anaerobic Metabolism Along An Arctic Peat Soil Profile, David A. Lipson, John M. Haggerty, Archana Srinivas, Ted K. Raab, Shashank Sathe, Elizabeth A. Dinsdale

Ted K. Raab

A metagenomic analysis was performed on a soil profile from a wet tundra site in northern Alaska. The goal was to link existing biogeochemical knowledge of the system with the organisms and genes responsible for the relevant metabolic pathways. We specifically investigated how the importance of iron (Fe) oxides and humic substances (HS) as terminal electron acceptors in this ecosystem is expressed genetically, and how respiratory and fermentative processes varied with soil depth into the active layer and into the upper permafrost. Overall, the metagenomes reflected a microbial community enriched in a diverse range of anaerobic pathways, with a preponderance ...


Real And Perceived Damage By Wild Turkeys: A Literature Review, Scott R. Groepper, Scott E. Hygnstrom Dr, Brandon Houck, Stephen M. Vantassel Jan 2013

Real And Perceived Damage By Wild Turkeys: A Literature Review, Scott R. Groepper, Scott E. Hygnstrom Dr, Brandon Houck, Stephen M. Vantassel

Scott R Groepper

As populations of wild turkeys (Meleagris gallopavo) have increased, the number of complaints about damage has increased. We conducted a literature review to determine real and perceived damage caused by wild turkeys in North America. Wild turkeys can cause damage to agricultural crops, such as corn (Zea mays L.), soybeans (Glycine max [L.] Merrill), wheat, and hay crops but the majority of actual damage is usually minor or caused by other wildlife, thus estimates of damage by wild turkeys often are inflated. Occasionally, wild turkeys damage specialty crops, turfgrass, or ornamental flowers that may have higher value than common agricultural ...


Site Assessment For Environmental Restoration, David A. Bainbridge Jan 2013

Site Assessment For Environmental Restoration, David A. Bainbridge

David A Bainbridge

Restoring degraded desert ecosystems is challenging but it can be done. The first key step is understanding the site history and understanding the disturbance and current site conditions. With this information the appropriate steps can be taken to improve the site ecosystem function and structure.


The Hudson’S Bay Company Brigades Of 1832-33 And The Malaria Epidemic In California, David A. Bainbridge Jan 2013

The Hudson’S Bay Company Brigades Of 1832-33 And The Malaria Epidemic In California, David A. Bainbridge

David A Bainbridge

The ecological and cultural impacts of the Hudson’s Bay Company fur brigades to California were long term and important, but the expedition of 1832-33 caused a catastrophe by introducing the intermittent fever. The “intermittent fever” led to mortality rates from 50-90 percent or more, and it is likely more than 30,000 people died from the fever in the affected areas of California.


West Nile Virus West Nile Virus Infection In American Robins: New Insights On Dose Response., Larry Clark Jan 2013

West Nile Virus West Nile Virus Infection In American Robins: New Insights On Dose Response., Larry Clark

Larry Clark

West Nile virus (WNV) is a vector-borne pathogen that was first detected in the United States in 1999. The natural transmission cycle of WNV involves mosquito vectors and avian hosts, which vary in their competency to transmit the virus. American robins are an abundant backyard species in the United States and appear to have an important role in the amplification and dissemination of WNV. In this study we examine the response of American robins to infection with various WNV doses within the range of those administered by some natural mosquito vectors. Thirty American robins were assigned a WNV dosage treatment ...


Diversity Of Plants And Animals In Mountain Systems In Tajikistan, Victor Roy Squires Dr, Neymatalo Safarov Dr Jan 2013

Diversity Of Plants And Animals In Mountain Systems In Tajikistan, Victor Roy Squires Dr, Neymatalo Safarov Dr

Victor Roy Squires Dr

Tajikistan, a landlocked country, is one of the world's centers of origin of cultivated plants and has a special role in the conservation of mountain biodiversity. The richness of biodiversity shows up at the genetic, species, population, and ecosystem levels. There are many relic and endemic species, with most of the components of biodiversity vulnerable to anthropogenic factors. Close cooperation across borders will be required for conservation of unique and threatened ecosystems in the Central Asian region. Proximate threats such as poaching, overfishing, illegal logging and overgrazing are causing irreversible damage to biodiversity in the Tajikistan hotspot. Threats stem ...


Use Of Anecdotal Occurrence Data In Species Distribution Models: An Example Based On The White-Nosed Coati (Nasua Narica) In The American Southwest., Jennifer K. Frey, Jeremy C. Lewis, James S. Stuart, Rachel K. Guy Jan 2013

Use Of Anecdotal Occurrence Data In Species Distribution Models: An Example Based On The White-Nosed Coati (Nasua Narica) In The American Southwest., Jennifer K. Frey, Jeremy C. Lewis, James S. Stuart, Rachel K. Guy

Jennifer K. Frey

No abstract provided.


Review Of Mark Bekoff's Ignoring Nature No More: The Case For Compassionate Conservation, Ian Werkheiser Jan 2013

Review Of Mark Bekoff's Ignoring Nature No More: The Case For Compassionate Conservation, Ian Werkheiser

Ian Werkheiser

No abstract provided.


Classification Of The Alterations Of Beaver Dams To Headwater Streams In Northeastern Connecticut, U.S.A., Denise Burchsted, Melinda D. Daniels Jan 2013

Classification Of The Alterations Of Beaver Dams To Headwater Streams In Northeastern Connecticut, U.S.A., Denise Burchsted, Melinda D. Daniels

Denise Burchsted

Of the many types of barriers to water flow, beaver dams are among the smallest, typically lasting less than a decade and rarely exceeding 1.5 m in height. They are also among the most frequent and common obstructions in rivers, with a density often exceeding ten dams per km, a frequency of construction within a given network on a time scale of years, and a historic extent covering most of North America. Past quantification of the geomorphologic impact of beaver dams has primarily been limited to local impacts within individual impoundments and is of limited geographic scope. To assess ...


Divergence In Thyroid Hormone Concentrations Between Juveniles Of Marine And Stream Ecotypes Of The Threespine Stickleback (Gasterosteus Aculeatus), Jun Kitano, Sean C. Lema Jan 2013

Divergence In Thyroid Hormone Concentrations Between Juveniles Of Marine And Stream Ecotypes Of The Threespine Stickleback (Gasterosteus Aculeatus), Jun Kitano, Sean C. Lema

Sean Lema

Background: Hormones regulate the expression of multiple phenotypic traits. Therefore,

divergence in hormone concentrations may lead to evolutionary changes in the coordinated

physiological and behavioural traits that comprise an organism’s integrated phenotype. Adults

of marine ecotypes of threespine stickleback (Gasterosteus aculeatus) have higher concentrations

of the thyroid hormone thyroxine (T4) than adults of stream-resident ecotypes (Kitano

et al., 2010). Thyroid hormones are well-established mediators of osmoregulation and migratory

behaviours in fish, and the difference in T4 concentrations indicates that changes in thyroid

hormone signalling may underlie the evolutionary and ecological divergence of migratory and

non-migratory ecotypes.

Questions: Is the ...