Wieteke A. Holthuijzen, a doctoral student in the Department of Ecology and Evolutionary Biology, is the first author on a new research study in PLOS on the diets of house mice and their conservation threat on islands.
Read the article here: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0293092
Dr. Angela Chuang, formerly of the Riechert lab, was consulted for this NY Times article on Joro Spiders, and whether current research is in fact proving how shy the species can be.
EEB Graduate Student Wieteke Holthuijzen received the best PhD poster award at the 50th Annual Meeting of the Pacific Seabird Group and also received the Chairs Choice Award for assistance in organizing the conference. Per their website, “The Pacific Seabird Group (PSG) is a society of professional seabird researchers and managers dedicated to the study and conservation of seabirds…PSG members include biologists, wildlife managers, post-docs, students and conservation biologists from 16 countries including the United States, Mexico, Canada and Japan. PSG annual meetings and publications provide forums where members can share their findings on all research topics related to Pacific seabirds, and discuss local and large scale conservation issues.”
Title: Determining arthropod consumption by Laysan Ducks to inform non-target mitigation efforts during rodent eradication
Authors: Wieteke Holthuijzen, Carmen Antaky, Beth Flint, Jonathan Plissner, Coral Wolf, Holly Jones
Abstract: The critically endangered koloa pōhaka (Laysan Duck, Anas laysanensis) in the Northwestern Hawaiian Islands has wild populations on Kamole (Laysan Island), Kuaihelani (Midway Atoll NWR), and Hōlanikū (Kure Atoll). Although its population and distribution have increased since its listing in 1967, the koloa pōhaka faces a new risk on Kuaihelani: non-target poisoning via a pending House Mouse (Mus musculus) eradication. After mice were observed attacking and depredating mōlī (Laysan Albatross, Phoebastria immutabilis) on Sand Island of Kuaihelani in 2015, plans to eradicate mice with rodenticide were quickly developed. To reduce exposure to rodenticide, ducks will be captured and translocated to Eastern Island (mouse-free) during eradication activities. Even so, ducks may risk secondary poisoning by ingesting arthropods that feed on brodifacoum bait. Therefore, it is crucial to monitor rodenticide residue in arthropods to determine when koloa pōhaka can be safely released post-eradication. Because duck diet is unknown on Kuaihelani, we used next-generation sequencing (NGS) to identify which arthropods ducks consume. We found that Sand Island’s ducks most frequently consume cockroaches (Blattodea), freshwater ostracods (Cyprididae), midges (Chironomidae), and isopods (Porcellionidae). Notably, Sand Island’s ducks consume entirely different arthropods from ducks on Kamole, which mainly eat flies (Diptera) and brine shrimp (Anostraca, Artemia sp.). Our study adds to the literature on the biology and ecology of translocated koloa pōhaka populations by using advanced techniques to uncover their diet with a high degree of taxonomic precision. In addition, our study serves as a model for risk mitigation during invasive rodent eradications.
Thirty volunteers came out to help remove invasive plants from Deans Woodlot (near Alcoa Highway, south of UT’s main campus) at the end of March. Everyone had a great attitude and was eager to remove invasive plants! Below are a some pictures of before, after, and the mound of material removed.
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.
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.
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.
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.”
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.
UTK EEB PhD student Sara Kuebbing was recently featured in the Knoxville News Sentinel for her work as part of the Tennessee Exotic Plant Pest Council. She uses an iPad app to identify and track species that are invading the US from elsewhere, typically after introduction by humans. Such species can dramatically affect functioning of ecosystems: examples in the United States include kudzu, zebra mussels, and pythons.