UMaine graduate student finds after last mass extinction, tiny fish ruled the sea

November 18th, 2015 11:26 AM

Orono, Maine — Andrew Galimberti, an entomology graduate student at the University of Maine, was part of a research team that discovered that bigger isn’t necessarily better for a fish during an extinction event.

Researchers from the University of Pennsylvania and UMaine found that for at least 40 million years following the last massive extinction, small, fast-reproducing fish may have dominated the planet’s oceans.

Approximately 359 million years ago, a bio-event referred to as Hangenberg, triggered a drastic and lasting transformation of Earth’s vertebrate community.

The event occurred during the late Devonian period — 416 million to 358 million years ago — and was characterized by high fish diversity, including some massive fish reaching 8 meters in length.

During this period, major climatic and ecological changes occurred, such as glacial events, sea level decreases and ecological invasions, which ultimately resulted in a major extinction event.

Recent evidence has shown that the Hangenberg event profoundly altered the course of vertebrate evolution, wiping out taxa that were dominant in the Devonian era. These findings, published in Science, could have implications for modern species today.

“Some large species hung on, but most eventually died out,” says Lauren Sallan, UPenn assistant professor of Earth and environmental science and lead author on the study.

Sallan and Galimberti were interested in the trends which characterized body size evolution in the Devonian, and how the Hangenberg event changed these trends.

“So the end result is an ocean in which most sharks are less than a meter and most fishes and tetrapods are less than 10 centimeters, which is extremely tiny. Yet these are the ancestors of everything that dominates from then on, including humans.”

One hypothesis the researchers explored for post-extinction size change is the “Lilliput effect” – the tendency for sizes to briefly decrease following an extinction event, then recover to normal. However, Galimberti noted, evidence for the Lilliput effect is limited, especially for vertebrates.

For the project, Galimberti and Sallan assembled a dataset of body sizes for 1,120 species of fish fossils spanning from 419 to 323 million years ago. The researchers gathered the body-size information from published papers, museum specimens, photographs and from incomplete fossils for which they could extrapolate a full size.

They performed a series of analyses to determine how body sizes changed throughout the Devonian and how the end-Devonian mass extinction affected these patterns.

The researchers found that after a period of steadily increasing body sizes throughout the Devonian, small fish, as the Lilliput effect suggests, dominated the early Mississippian, says Galimberti. However, recovery of large sizes did not occur in the Mississippian — sizes remained small or, in some cases, decreased throughout for at least 40 million years.

By the end of the Devonian, some fish were as large as school buses, says Sallan. “You had some vertebrates that are small, but the majority of residents in ecosystems, from bottom dweller to apex predator, were a meter or more long.”

“These large fish, though, were “dead clades walking” — clades that would fail to diversify and eventually become extinct, in contrast to the smaller survivors which continued to diversify throughout the Mississippian and beyond,” said Galimberti.

This suggests that, even if a large organism is able to survive an extinction event, it may remain vulnerable to extinction, he says.

Generally, larger organisms tend to be more prone to extinction due to greater energy requirements, and production of fewer offspring which results in smaller population sizes. These factors make large organisms less likely to adapt to drastic changes in the environment.

“Conversely, small organisms have large populations and high reproductive ability, increasing their chance at survival and their ability to adapt,” said Galimberti.

“As extinctions continue, we may see similar patterns to those after the Hangenberg — more small species, drastic diversity changes, and a long period of time before ecosystems stabilize and recover,” says Galimberti. “Future research should determine how widespread these patterns are, both in the fossil record and today,” says Galimberti.

Today, human-driven environmental changes have led to great losses in many fish and other animals, especially large ones. With many global fish populations in danger and with some ecologists concerned the planet is on the brink of a sixth major extinction event, this time caused by humans, Sallan warns that these results should raise a red flag about how long large species might take to recover.

“These disturbances are shifting natural selection so that smaller, faster-reproducing fish are more likely to keep going, and it could take a really long time to get those bigger fish back in any sizable way,” says Sallan.

The University of Pennsylvania, Kalamazoo College, the University of Michigan and the Michigan Society of Fellows supported the study.

University of Pennsylvania’s full press release is available online.

Media Release
Nov. 17, 2015
Contact: Amanda Clark, 207.581.3721

To protect ecosystems, Gill says start with largest inhabitants

November 9th, 2015 12:27 PM


To protect ecosystems, Gill says start with largest inhabitants

The extinction of mammoths, ground sloths and other large plant-eaters thousands of years ago triggered shifts in global habitats and changes in ecosystems, says University of Maine paleoecologist Jacquelyn Gill.

The assistant professor in the School of Biology and Ecology and the Climate Change Institute says fossils and other records from the deep past provide evidence of widespread short- and long-term changes in community composition, structure and function after large herbivores went extinct.

Essentially, she says, extinctions are records of completed grand natural removal experiments. And the records indicate long-term changes after megafauna extinctions included reduced seed dispersal, which continues to influence plant species, as well as an increase in fires.

“At the end of the last Ice Age, we lost half of the large mammals in North America larger than a German Shepherd, and the forests and grasslands they inhabited noticed the difference,” Gill says.

“Large herbivores, from mammoths to elephants, play special keystone roles in ecosystems; when we lose them, we lose all the services they provide, from spreading nutrients to creating patches where many different plants can thrive.”

It’s important to understand large herbivores’ contributions to ecosystems, Gill says.

Today’s large plant-eaters, including elephants and rhinos, influence the abundance of woody species, as well as impact plant diversity, nutrient cycling and other animals. They also are among the most threatened species on the planet due to reduced habitat, climate change and hunting.

“There’s evidence from modern studies that healthy populations of native large herbivores increase plant biodiversity, and may even help ecosystems be more resilient to climate change,” Gill says.

“If you want to protect an entire ecosystem, start with protecting its largest inhabitants.”

Gill is part of an international team that authored “Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation.” It is featured in the Oct. 26 edition of the Proceedings of the National Academy of Sciences of the United States of America.

Elisabeth S. Bakker of the Netherlands Institute of Ecology is lead author of the study.

Other participating researchers are: Christopher N. Johnson of the University of Tasmania in Australia; Frans W. M. Vera, of the University of Groningen in The Netherlands; Christopher J. Sandom of Oxford University in the United Kingdom; Gregory P. Asner of Carnegie Institution for Science in California and Jens-Christian Svenning of Aarhus University in Denmark.

Contact: Amanda Clark, 207.581.3721, Beth Staples, 207.581.3777

Female invaders are ecologically stronger than males

November 9th, 2015 11:59 AM

Female invaders are ecologically stronger than males

ORONO, Maine — Males and females of many different species are often visibly different from one another. Scientists call these differences ‘sexual dimorphism‘ and it has been studied extensively by evolutionary biologists all of the way back to Charles Darwin.

But what is not yet clearly understood is how these differences impact an entire ecosystem.
Researchers at the University of Maine and University of California at Santa Cruz recently published a paper suggesting that sexual dimorphism and the ratio of females to males in populations of western mosquitofish can shape the ecological impacts the invasive fish has on an ecosystem.

The researchers found that female-dominated populations of mosquitofish have a greater ecological impact compared to males.

Western mosquitofish, originally from North America, have been widely introduced around the world to control mosquitos that spread diseases such as West Nile Virus and malaria.

But their wide introduction created unintended consequences for native biodiversity and changes in pond ecosystems, resulting in the species being listed among the world’s 100 worst invasive species by the International Union for Conservation of Nature.

“Mosquitofish are known to have detrimental effects on native freshwater fauna, and in a lot of places there are efforts to control and extirpate them,” Eric Palkovacs, assistant professor of ecology and evolutionary biology at the UC Santa Cruz, said. “It’s been called the ‘plague minnow’ in Australia and New Zealand because its effects are so drastic.”

In their experiments, the researchers varied the ratios of mosquitofish sexes introduced into experimental pond ecosystems and compared them to ponds without the invasive fish. The experimental pond ecosystems contained sediments, algae, zooplankton and other naturally colonizing invertebrates and amphibians.

“One of the interesting population patterns that we see in mosquitofish is just how different populations can be in their proportions of males and females,” Michael Kinnison, professor of evolutionary biology at the UMaine, said. “We have been frustrated on more than a few occasions by how challenging it can be to capture one sex when you already have buckets of the other.”

This variation in sex ratios is likely caused by differences in size, behavior, longevity and preferences of predators like birds and other fish, explains Kinnison.

The scientists found that female-dominated populations changed their pond communities more than male-dominated populations, resulting in stronger ‘trophic cascades’.

Trophic cascades are changes in communities that occur when predators, like mosquitofish, reduce the abundances of their prey, leading to increased abundances of those prey’s prey, producing a flip-flopping effects down the food chain.

“We knew from past work that mosquitofish introductions produce trophic cascades all of the way down to the algae at the base of the food chain,” said Kinnison. “What was surprising, is that female-biased populations significantly magnified essentially all of those cascading effects.”

The researchers found that populations with more females exacerbated cascade effects on everything from zooplankton and algae to temperatures and pH (a measure of water acidity).

The authors of the study indicated this pattern is consistent with some of the known differences between female and male mosquitofish. Female mosquitofish are larger and prefer larger prey, have higher feeding rates and spend more time foraging in the presence of other females when males instead devote more time to finding mates.

The findings from this study have both general and applied implications, says Kinnison.

Sexual dimorphism and sex ratio variation are very common in fishes and other taxa, so this work could provide encouragement to consider the ecological consequences of these patterns in many other species.

From an applied standpoint, says Kinnison, the approaches used to control mosquitofish and other invasive species — such as trapping or introductions of sterile males to reduce fertile matings — can inadvertently shift sex ratios and in doing so alleviate or intensify the ecological effects of such invaders.

Understanding the population biology and ecological effects of such invaders is imperative to predicting their impacts and managing them. Not all populations of invaders are equally harmful, so finding out what makes some worse than others is important.

The experiments for this study were conducted at UCSC’s Long Marine Laboratory with mosquitofish collected from a California mosquito vector control district.

The paper, titled “Sex ratio shapes the ecological effects of a globally introduced freshwater fish,” was published October 21 in Proceedings of the Royal Society B.

Other authors included Heather Arnett, graduate student at UMaine, and David Fryxell and Travis Apgar, graduate students at UC Santa Cruz. The research was funded by the National Science Foundation, UC Santa Cruz and the Maine Agricultural and Forest Experiment Station.


Media release
Oct. 27, 2015
Contact: Michael Kinnison, 207.581.2575; Amanda Clark, 207.581.3721
Photo credit: Dave Fryxell, UC Santa Cruz

Bog Boardwalk Nature Walk

September 23rd, 2015 12:09 PM

On Saturday, October 3rd, Professor Emerita Christa Schwintzer will be leading a fall plant walk along the boardwalk in Orono, located in the Rolland F. Perry City Forest. Throughout the walk participants will observe changes that plants undergo during the fall, allowing them to survive the winter and then quickly resume growth in the spring. Participants will also be exposed to examples of bog plant adaptations that allow them to live in the wet, low nutrient conditions where most other plants are not able to survive.
The walk will take place from 9-10:30 am, starting at the beginning of the boardwalk, and it is free! Space is limited to 12 participants and registration is required. If you are interested, please email with “Boardwalk nature walk” on the subject line, your name, and a telephone number where you can be reached in case of foul weather.
All are welcome to attend!

NPR Interviews Drummond for Report on Popularity of Nordic Berries in Asia

September 21st, 2015 11:55 AM

Frank Drummond, an entomology specialist with the University of Maine Cooperative Extension and a UMaine professor of insect ecology, was quoted in the NPR report, “Asian countries have Nordic berry fever, and Finland can’t keep up.” Every day, about 7,000 Thai workers search the woods of Finland and Sweden for bilberries, lingonberries and cloudberries. Using buckets and scooping tools, they each gather up to 270 pounds of berries, according to the report. Even with each person picking 270 pounds a day, it isn’t enough for the high demand at Nordic berry companies, the report states. The berries are used in food such as pies, jams, ice cream and juice, as well as health and beauty products. Domesticating the Nordic berries — which would involve breeding and selecting to create something similar to the highbush blueberry — is a possibility to help with the demand, the report states. “It’s such a complicated process that it could take several decades for the Scandinavian countries to figure out what is the best way to grow the plant without adverse effects,” Drummond said.

SBE Seminar Series Schedule for 2015

September 17th, 2015 2:25 PM

The School of Biology & Ecology is pleased to present this years Friday Seminar Series schedule for fall 2015. The purpose of these seminars is to highlight an array of leading research fields and interests from professors and researches located all over the country.
Seminars will be held on Fridays at 3:00 pm in 107 Norman Smith Hall, unless otherwise noted. Light refreshments will be served at 2:50 pm. All are welcome to attend!

The schedule is located here.


Fall Seminar Schedules for Related Departments

September 15th, 2015 2:46 PM

Click on the links below to view the schedule

Wildlife, Fisheries, and Conservation Biology

The School of Forest Resources

Ecology and Evolution of Everything Seminar Series Details

September 3rd, 2015 2:27 PM

What: A weekly seminar-style, semi-formal gathering of ecologists (broadly defined). Students can take the class for credit (EES 590), but everyone — students, staff, faculty, and postdocs — are welcome to attend. We discuss papers, share data, do stats throwdowns, practice talks, etc.

Who: Hosted by Jacquelyn Gill, Brian Olsen (SBE), Brian McGill (SBE), Tim Waring (Econ), and Hamish Greig (SBE). Folks from all disciplines amd career stages welcome.

Where: Norman Smith 101

When: Thursdays, 11 am to 12:15 pm (our first planning meeting is this week, and we’ll sign up for slots, so bring your calendar!)

Why: It’s a great way to meet folks, share ideas, connect across departments, get feedback on papers or talks, and learn from your peers in an informal setting. Sometimes, there are cookies.

Smith Featured in UMaine Today

June 24th, 2015 4:25 PM

Photo Michelle Smith TeachingSchool of Biology and Ecology professor, Michelle Smith, is featured in the Spring/Summer 2015 issue of UMaine Today. Smith’s work on active learning in large enrollment courses is at the forefront of current science education research.

Read the full article here.

Jacquelyn Gill Featured on PBS Program

June 23rd, 2015 4:43 PM

School of Biology and Ecology professor, Jacquelyn Gill, is featured on the PBS series, First Peoples. The series premieres June 24th at 9pm.

More information can be found here.