Ecology & Evolutionary Biology

Home » postdoc

postdoc

NSF Award and Recognition for EEB

by

EEB undergraduate Justin Baldwin and EEB graduate student Maggie Mamantov (Sheldon Lab) both received honorable mentions in the prestigious National Science Foundation Graduate Research Fellowship Program. This program selects early career students with high potential in science.

Amanda Wilson Carter (postdoc, Sheldon Lab) was awarded an NSF Postdoctoral Research Fellowship in Biology! Using dung beetles, she will integrate thermal plasticity across life stages with maternal behavior to understand the mechanisms driving responses to increased temperature variation.

Congratulations!

50th Anniversary of Island Biogeography Studies

by

In honor of the 50th anniversary of the seminal Simberloff and Wilson island biogeography studies, the Bulletin for the Ecological Society of America published a special extended edition of their “Paper Trail” series in October. In this series, young researchers tell stories of how a particular paper influenced them, and the original authors of the papers in turn describe their experiences with the paper.

For this special edition, a collection of researchers, ranging from graduate students to full professors, describe how the Simberloff and Wilson 1969 papers influenced their careers. From our department, Jeremiah Henning, Jordan Bush (graduate students), Christy Leppanen (lecturer and post doc), and Kimberly Sheldon (assistant professor) all contributed to this section. Dan Simberloff and Edward O. Wilson then wrote a reflection on the original paper, complete with photographs and stories from the mangrove experiments. 

A Pioneering Adventure Becomes an Ecological Classic: Editor’s Note
(overview, by Young, Stephen L.)

A Pioneering Adventure Becomes an Ecological Classic: The Arising and Established Researchers
(Authors: Henning, Jeremiah A.; Leppanen, Christy; Bush, Jordan; Sheldon, Kimberly S; Gotelli, Nick; Gravel, Dominique; Strauss, Sharon)

A Pioneering Adventure Becomes an Ecological Classic: The Pioneers
(Authors: Simberloff, Daniel; Wilson, Edward)

 

Buried in their Work!

by

EEB Volunteers get Dirty Digging Roots to Help with Invasive Species Research

Christy Leppanen, Dan Simberloff, and Kimberly Sheldon pose in front of a southern Japanese hemlock, Tsuga sieboldii.

In July, a group of EEB faculty, staff, graduate and undergraduate students, family, and friends helped dig roots as part of a study of belowground communities associated with hemlock trees.  Prof. Daniel Simberloff and Christy Leppanen (EEB lecturer and postdoc), are collaborating with Melissa Cregger (Oak Ridge National Laboratory) to characterize microbial communities associated with native and non-native hemlocks.  Some of the trees are vulnerable to infestation by the hemlock woolly adelgid, but some appear to be resistant.

Distribution of hemlock species (Tsuga spp., Family: Pinaceae)

The hemlock woolly adelgid (Adelges tsugae or HWA) is a sap-feeding insect introduced in the 1950s from Asia to eastern North America, where it kills native eastern (Tsuga canadensis) and Carolina (T. caroliniana) hemlocks.  In Asia and in western North America, HWA feeds on, but does not kill, hemlocks that are native there.  Therefore, aspects of communities where HWA is native and trees that are apparently resistant are studied to help understand impacts and develop management approaches where HWA is introduced.

EEB graduate students Chelsea Miller (Kwit Lab) and Angela Chuang (Riechert Lab) collect roots and soil from under an eastern hemlock, Tsuga canadensis.

Simberloff and Leppanen traveled with a group of 14 volunteers to North Carolina State University’s Mountain Horticultural Crops Research and Extension Center, in Mills River, North Carolina, to collect roots and associated soil from native and non-native hemlocks that are vulnerable or appear resistant to HWA infestation.  From these samples, Cregger will characterize microbial communities: archaea, bacteria, and fungi associated with the different trees.  The team will then meet to discuss the results and consider implications and next steps.

Kylie Hannahs digs under a southern Japanese hemlock, Tsuga sieboldii, with Chase Steele, EEB undergraduate research assistant in the Fitzpatrick and Simberloff Labs.

Microbial communities influence and can indicate associated host organism health.  Microbial diversity and composition can influence large-scale nutrient fluxes across ecosystems.  Loss of native hemlocks, or even HWA infestation of living hemlocks, may impact important ecosystem-level processes as a result of losses or changes to associated microbial communities.  Additionally, suggested replacement of our native hemlocks with non-native species such as the Chinese hemlock (T. chinensis) may have ecosystem-level implications if microbial communities associated with the Chinese hemlock differ.  Microbial communities associated with non-native “replacement” trees may not only prevent the return of native ecosystem dynamics but may also influence our native ecosystems in entirely new and unpredictable ways.

Ruth Simberloff and Frank Scott examine roots under a Himalayan hemlock, Tsuga dumosa.

Fine roots are collected to characterize microbial communities associated with different hemlock species.

T.J. Rogers, SULI Intern working with Melissa Cregger at Oak Ridge National Laboratory, and EEB undergraduate researchers Jake Lockyer and Casey Fellhoelter finish work with a Chinese hemlock, Tsuga chinensis. (SULI, Science Undergraduate Laboratory Internships)

EEB student workers Damon Christensen and Michael Ellison excavate under an eastern hemlock, Tsuga canadensis.

Scientific American Blog Highlights UT Research

by

The popular Scientific American Blog has posted an article about bat research done by grad student Jessica Welch (McCracken and Simberloff labs) and NIMBioS postdoc Jeremy Beaulieu.

The article, “Are Bats Facing a Hidden Extinction Crisis? A new way of calculating bat extinction risk reveals previously hidden conservation priorities,” can be viewed here.

Tennessee Today also did an article covering the blog post.

Eppley Foundation Grant Awarded for Hemlock Woolly Adelgid Research

by

Professor Daniel Simberloff and postdoc Christy Leppanen have been awarded a $16,500 grant from The Eppley Foundation for Research for their proposal:  Effects of Evolutionary Ecology and Ecosystem Variability in Native and Introduced Predator-Prey Systems.

Print

Click image to view larger version.

Simberloff and Leppanen study interactions involving introduced predators and their prey, the hemlock woolly adelgid, Adelges tsugae, or HWA.  A sap-feeding insect native to Asia, HWA has spread to eastern North America where infestations have caused sharp declines in native hemlocks, including in some locations complete losses of eastern hemlock and Carolina hemlock, which is now vulnerable to extinction.  Predators transplanted from Asia are considered a long-term solution.  Little is known, however, about HWA and predator behavior and interactions in their native or introduced ranges.

Print

Click image to view larger version.

Funds from the Eppley Foundation will be used to study HWA where it is introduced and native, where trees seem relatively unharmed by the insect.  Hemlock species, climate, and invertebrate communities differ between native and invaded areas.  Simberloff and Leppanen are interested in understanding what influences HWA population size, for example, whether predators experience different levels of success in their native and introduced habitats, much like HWA imparts different levels of damage where it is native and introduced.  They suspect that HWA control likely involves a variety of influences and interactions that vary by location.  In their research, they will evaluate interactions involving HWA, its predators, and other native and non-native species in different locations.  For example, they have documented and will assess the significance of predator entrapment in droplets of HWA’s liquid waste, a previously unreported phenomenon that may influence predator success and thus HWA populations; and, if the outcome of entrapment differs by predator species, HWA populations may differ further where predator communities differ.  They will also consider interactions among mites, lichen, and another invasive predator, the multicolored Asian lady beetle, Harmonia axyridis, which shares its native range with HWA.

The results of this research will be included in a review of what is known about evolutionary ecology and ecosystem variability in native and non-native HWA systems relevant to its population size and impacts.  This is a model system with broad applicability in education; information from the review will also be used to develop a teaching lesson.

The Eppley Foundation for Research was incorporated in 1947 for the purpose of “increasing knowledge in pure or applied science…in chemistry, physics and biology through study, research and publication.”  The Foundation funds projects in biological and physical sciences. Particular areas of interest include innovative medical investigations, endangered species and ecosystems in the U.S. and abroad, and climate change.

 – From The Eppley Foundation for Research website

NSF Postdoctoral Fellowship for Heberling

by

Postdoc J. Mason Heberling (Kalisz Lab) has been awarded a two-year National Science Foundation postdoctoral fellowship.  The proposal, entitled “Leveraging ventures of herbarium data to track plant invasion processes: trait shifts, local adaptation, and rapid evolution,” was funded by NSF’s Postdoctoral Research Fellowship in Biology, Interdisciplinary Research Using Biological Collections program.

The host institutions for this fellowship are the Carnegie Museum of Natural History and the University of Tennessee Knoxville, and the sponsoring scientists are Dr. Stephen Tonsor (Carnegie) and Dr. Susan Kalisz (UT).  Heberling will use herbaria worldwide to track trait shifts of invasive plants in the Eastern US through space and time.

For more information, please read his abstract, below.  Congratulations, Mason!

ABSTRACT:

The globalization of human activities has reshuffled plant communities across the world, resulting in substantial environmental damage and economic losses. This research leverages centuries of biological collections alongside recent advances in functional trait ecology to understand fundamental plant invasion processes. The frequency and importance of trait shifts following plant introductions, the direction and rate of these potential trait changes, and the degree to which local adaptation influences invasion success remain largely unknown. This project utilizes the extensive collection of the herbarium of the Carnegie Museum of Natural History, supplemented with specimens from other herbaria worldwide. These specimens of introduced and native Eastern US species, collected from early 1800s to today, are being used to measure traits relating to carbon gain, resource-use, reproductive/dispersal ability, and phenology across space and time. This novel approach allows the ability to track species trait shifts through space and time – a task that would otherwise be impossible without collections. Main research objectives include using these data to track phenotypic change through the course of plant invasion and assess the role of local adaption to understand and predict species success. Advancing the use of herbaria to the rising field of trait-based ecology will substantially expand existing global trait databases to facilitate research on fundamental biological questions at a large scale.

The training objectives of this fellowship include the development of skills associated with herbarium methods, recent statistical advancements, geographic information systems (GIS), and software development for efficient specimen georeferencing. Career development activities include building research collaborations, expanding past research to include herbarium data and evolutionary analyses, and encouraging diverse participation to highlight the importance of biological collections as a vital source of knowledge to the broader community. Despite availability and relevance, collections-based science has been reported on the decline. This project addresses this disconnect through interaction with community organizations in Western PA, including local elementary education programs and museum docent training.

Hemlock Woolly Adelgid Press Release

by

FIRST REPORT OF HEMLOCK WOOLLY ADELGID EGGS HATCHING IN EARLY WINTER, POSSIBLY LINKED TO CLIMATE WARMING

(View the related Tennessee Today press release.)

Newly discovered much earlier reproduction of this forest pest may explain why it is invasive, reveal why control has failed, and impede future control.

HWA Infestation

Hemlock woolly adelgid (Adelges tsugae) infestation on the underside of an eastern hemlock (Tsuga canadensis) branch in Knox County, Tennessee.

A sap-feeding insect native to Asia, the hemlock woolly adelgid (Adelges tsugae) or HWA was first found in 1951 in eastern North America, where it has since devastated native hemlock populations. HWA does not kill hemlocks in its native range, and why it devastates hemlocks in eastern North America has not been determined.

Like its aphid relatives, HWA has a complex life cycle. Reproduction alternates through several sexual and asexual generations. Each generation is made up of a variety of life forms. Completing two generations each year on hemlock, adults lay eggs that hatch from March through June, then develop though four stages before they mature and lay eggs that hatch from May through July. Until now, scientists documented HWA eggs hatching only from March through July.

HWA Crawlers

Hemlock woolly adelgid (Adelges tsugae) 1st instar nymphs, called “crawlers,” emerging from a “woolly” mass where an adult female lays eggs inside.

The newly documented activity occurred in eastern Tennessee during and after record high temperatures, attributed to global climate change and El Niño conditions, where December’s average mean was 53°F with 14 days at least 65°F. Although not proven to be the reason for this newly documented HWA activity, temperature likely contributed in some way. Temperature influences the rate of insect development, distribution, and abundance.  Higher temperatures shorten life cycle stages, sometimes increasing the number of generations each year. More generations create more offspring and may increase insect populations. Alternatively, insect populations may crash when put out of sync with their hosts or when they develop new interactions preventing their survival.

HWA Eggs

Hemlock woolly adelgid (Adelges tsugae) eggs revealed inside “woolly” mass.

When University of Tennessee researchers Christy Leppanen and Daniel Simberloff discovered eggs hatching in December, they followed populations and determined that this winter’s HWA populations reproduced earlier and more quickly than previously documented.

Reproduction outside of recognized cycles can counteract management because control relies on accurate predictions of pest reproduction, knowing what life stages are present when, so they can be targeted at the most effective times. We are caught by surprise when pests break the rules.

“We visit only a few locations out of the introduced range that extends from Georgia to Maine and couldn’t have been so lucky to happen across the first instance of early winter reproduction,” Leppanen said. “This likely occurred before, possibly increasing populations at times or in numbers that overwhelmed existing population controls, including beetles deliberately introduced to eat them, and contributed to HWA’s escalation from ‘introduced’ to ‘invasive’ in the East.”

Hemlock woolly adelgid (Adelges tsugae) 1st instar nymphs implanted to feed at the base of eastern hemlock needles.

Hemlock woolly adelgid (Adelges tsugae) 1st instar nymphs implanted to feed at the base of eastern hemlock needles.

Events like this challenge current HWA control focused on matching natural enemies like the introduced beetles with HWA population cycles. Control using natural enemies has not yet proven successful, possibly because HWA reproduction has not been sufficiently synchronized with enemies able to respond in time, place, and densities necessary to reduce HWA populations. And while earlier reproduction that occurs regularly is predictable, reproduction on the fly in response to changing conditions, such as temperature fluctuations, is difficult to anticipate. So, the frequency and regularity of “extragenerational” reproduction must be understood.

After their discovery, Leppanen sent a mass email to a group of HWA researchers and managers on December 31, 2015, New Year’s Eve. An immediate response came via dozens of “Out of Office” replies. Simberloff asks, “Could similar events in other years have gone unrecorded because HWA life cycles were not synchronized with researcher activity periods?”

Dr. Christy Leppanen is a Postdoctoral Research Associate working in the laboratory of Dr. Daniel Simberloff, the Nancy Gore Hunger Professor of Environmental Studies, in the Department of Ecology and Evolutionary Biology at the University of Tennessee.

Old growth eastern hemlock (Tsuga canadensis) in Knox County, Tennessee.

Old growth eastern hemlock (Tsuga canadensis) in Knox County, Tennessee.

Fresh, vibrant eastern hemlock (Tsuga canadensis) growth in Knox County, Tennessee.

Fresh, vibrant eastern hemlock (Tsuga canadensis) growth in Knox County, Tennessee.

 

 

 

Best Paper in Theoretical Ecology

by

Jiang Jiang (NIMBioS fellow and Classen Lab postdoc) and Don DeAngelis (adjunct) have received the Ecological Society of America’s 2014 Outstanding Ecological Theory Paper Award.  Their winning paper,  “Strong species-environment feedback shapes plant community assembly along environmental gradients,” was published in the journal Ecology and Evolution in 2013 (3: 4119–4128).

“In their clearly-written paper, the authors make direct linkages to problems in plant ecology, while building a general theoretical model that addresses a key issue, not just in plant ecology, of feedbacks between organisms and their environment. Through well-designed analyses of an elegant model, they found that “ecological engineers” (species that modify the environment to their own benefit) can affect the diversity of the competitive community they inhabit, and that the direction of this effect depends critically on the extent to which the community is closed to immigration and on the spatial heterogeneity of the environment. These novel results should are likely to foster further theoretical research and generate some fine hypotheses that will motivate experimental and field studies.”

“The Theoretical Ecology Section of the Ecological Society of America sponsors an annual award for an outstanding published paper in ecological theory.  Papers with a print or electronic publication date in either of the two years preceding the year of the award are eligible.”

Mulholland Endowment Challenge Match

by

Friends and colleagues of Pat Mulholland have an opportunity to double the impact of their contributions in support of the Pat Mulholland Post-Doctoral Endowed Fellowship. A donor has generously pledged to give up to $10,000 in this challenge match donation.  Any contributions we make that exceed this $10,000 challenge also will be placed in the Mulholland Endowment Fund. 

Throughout his career, Dr. Patrick Mulholland was a strong advocate for early career scientists as well as for collaboration between University of Tennessee and Oak Ridge National Laboratory (ORNL). In recognition of Dr. Mulholland’s efforts, this endowment will support a postdoctoral fellow for one to three years to conduct collaborative research in ecology or environmental sciences, focusing on pressing environmental issues related to global change, with faculty in the Ecology and Environmental Biology Department (EEB) at UT and staff scientists at ORNL.  For more information about Pat Mulholland, please read the Mulholland Endowment Article from page 2 of the 2012 EEB Newsletter.

To give to the Mulholland Post-Doc Fellowship Endowment Challenge

By Mail

Please make checks payable to “The University of Tennessee Foundation” and indicate “Mulholland End. / MULHO_P” in the memo line.

Mailing address:           College of Arts and Sciences Development Office
                                          2524 Dunford Hall
                                          Knoxville, TN 37996-4000

By Phone

To make a pledge or give a gift using your VISA, Mastercard, or Discover credit card, you may call the office at (865) 974-2295.

Online

Visit volsconnect.com/patmulholland to donate online using our secure website.

Stock Gifts

There can be significant tax advantages for donors choosing to transfer highly appreciated (long-term) securities to the UT Foundation as a charitable gift. The value of your gift depends upon the market price of your assets when they are given. Please contact Cathy Dodge (865-974-4321) or Judy Miller (865-974-2557) for more information on gifts of securities.

 One-time donations and multi-year pledges are welcome.

Bats go where the food is

by

A recent paper in PLOS ONE by dept. head Gary McCracken and colleagues, including former UTK EEB grad students Veronica Brown and Paula Federico, as well as UTK postdoc Melanie Eldridge, analyzed insect DNA in bat feces. Their work suggests that bats change foraging locations to match prey abundance. It also supports previous researchers’ findings that bats contribute substantially to agriculture, providing services that can amount to 12% of the value of a crop.

Abstract: 
The role of bats or any generalist predator in suppressing prey populations depends on the predator’s ability to track and exploit available prey. Using a qPCR fecal DNA assay, we document significant association between numbers of Brazilian free-tailed bats (Tadarida brasiliensis) consuming corn earworm (CEW) moths (Helicoverpa zea) and seasonal fluctuations in CEW populations. This result is consistent with earlier research linking the bats’ diet to patterns of migration, abundance, and crop infestation by important insect pests. Here we confirm opportunistic feeding on one of the world’s most destructive insects and support model estimates of the bats’ ecosystem services. Regression analysis of CEW consumption versus the moth’s abundance at four insect trapping sites further indicates that bats track local abundance of CEW within the regional landscape. Estimates of CEW gene copies in the feces of bats are not associated with seasonal or local patterns of CEW abundance, and results of captive feeding experiments indicate that our qPCR assay does not provide a direct measure of numbers or biomass of prey consumed. Our results support growing evidence for the role of generalist predators, and bats specifically, as agents for biological control and speak to the value of conserving indigenous generalist predators.