Twenty-Year Study Shows How Climate and Habitat Change Impact One Mantid Species
By Paige Embry, Entomology Today
Ask someone what they know about praying mantids and chances are they’ll bring up the female biting the male’s
head off during mating. It happens, albeit only about 17 percent of the time, but those deaths can be a surprisingly
useful tool when studying mantid population changes over time. It’s one of the pieces of information tracked by
Lawrence Hurd, Ph.D., a professor of biology at Washington and Lee University, during a 20-year study
(1999-2018) of Tenodera aridifolia sinensis, the Chinese praying mantid.
The results were published in January in Annals of the Entomological Society of America.
In the last few years, studies finding widespread declines in insect abundance have made headlines. Hurd’s
long-term study uses one insect in one northern Virginia field to show how such declines can happen. Although the study only followed one species, Hurd and coauthorsnote that the findings should apply to other insects and spiders with a similar life cycle.
For this study, Hurd made good use of his resources. He had an insect of unusual size (7-10 centimeters) that beginners (his college ecology lab students) could easily recognize and catch. He also had a nearby field beginning its natural succession, which functioned as a laboratory because the mantids couldn’t easily escape from it. No other suitable fields were close by, and the mantids aren’t very mobile.
Five times between 1999 and 2018, on approximately the same day in September, Hurd sent his students across the
field in a “skirmish line” to collect, mark, and note every possible T. a. sinensis. Hurd writes in an email, “I always
try to base it [the class] on gathering good, usable data instead of just make-work data collection on a question that
has already been answered.”
To assess the reproductive success of the mantids, they went back after the first frost to collect the oothecae (eggs
laid in a gooey substance that hardens into a protective case). They brought the oothecae back to the lab, weighed them, and then returned them to the field. For the oothecae found on the stems of herbaceous plants, that meant “tying [them] on with sewing thread run through the dried foam surrounding the eggs.” Mantids do well in flowery fields with lots of arthropod prey. When succession trends in an area lead to more trees, the population of mantids should shrink. Over the 20 years of this study, two-thirds of the open field area was replaced by trees, and the number of mantids decreased dramatically.
However, succession was not the only factor impacting the mantids—climate change was as well. When a Chinese praying mantid lays her eggs, the sex ratio is even. By the time the mantids reach adulthood, males outnumber females. Once mating begins, the percentage of males starts to fall, prey to the females as well as any other
predators in the field. Eventually, the females become more common. Even though Hurd and the students sampled on essentially the same calendar day (September 12, 13, or 14) each year, they found that the proportion of males to the total population declined from more than 60 percent in 1999 to about 25 percent in 2018, showing that the mantids were further along in their life cycle.
It’s no surprise. For the last 40 years the growing season in northern Virginia has gotten longer and the summers hotter, so the mantids both hatch and reach maturity earlier. This means that some eggs may hatch before frost can put them into diapause, leading to death of the young nymphs and potentially adding to the population losses caused by the successional change.
In 2018, Hurd and his students found only three oothecae. In the fall of 2019, he saw no mantids, and found no oothecae after the first frost.
This study demonstrates the potential double whammy of habitat loss—even a naturally occurring one—and climate change. Hurd writes, “People are becoming worried about having to include insects in the mass extinction episode that many (including me) feel is already underway.” He says when he talks about this, people often respond with, “‘We gotta worry about bugs, too?'”
Unfortunately, as this study illustrates, the answer to that question is “yes.”
Find this article in Entomology Today here.
Find other articles on declines in insects and biodiversity on the Reading Corner page.
World’s fireflies threatened by habitat loss and light pollution, experts warn
Lightning bugs cannot signal to one another to mate if there’s too much light at night.
By Ben Guarino
Feb. 3, 2020 at 12:22 p.m. EST
(shared by Charlene Uhl, Class X)
Nearly 2,000 species of fireflies flit, crawl and sparkle across the planet. Some of these lightning bugs are doing fine. Others are not.
A survey of 49 of the world’s firefly experts, published Monday in the journal BioScience, has identified the most serious threats to the animals. Habitat loss, in almost all of the regions surveyed, is a problem. Other threats include artificial light, which disturbs their mating rituals; pesticides, which can harm the insects or their invertebrate prey; and water pollution, for species that have an aquatic stage.
The report is not a census of the world’s firefly population. But it is “the very first time that we’ve gathered information — this is based on expert opinion — about what the most prominent threats are to the fireflies in different parts of the world,” said study author Sara M. Lewis, a biologist at Tufts University.
“For the last decade or more, people have been anecdotally reporting that they’re not seeing fireflies where they used to,” Lewis said. “Good census data over the past few decades” exists for some species, such as Malaysia’s synchronous fireflies and the common European glowworm, Lewis said. “We know that those populations are, in fact, declining.”
Elsewhere, however, firefly literature remains “kind of obscure,” she said, and the research community is relatively small.
This poll of firefly experts was the “next best thing” to traveling back in time to count firefly populations, said University of Florida entomologist Marc Branham, who was not a member of the research team. He has been told many anecdotes of missing fireflies. And often, he said, they’re believable. Fields once full of flashing insects “are so obvious, in a sort of a sad sense,” when the light vanishes, he said.
“One of the things we’ve kind of taken for granted is that fireflies will always be here,” said naturalist Ben Pfeiffer, founder of the nonprofit Firefly Conservation & Research organization and one of the firefly experts who was surveyed. “And we’ve been terribly wrong about that.”
In 2018, the International Union for Conservation of Nature created the Firefly Specialist Group, co-chaired by Lewis, to determine whether certain firefly species should be listed as threatened or endangered. “That’s something we’ve never seen happen for a firefly species,” Fitchburg State University biologist Christopher Cratsley said. Cratsley was not a member of the study team.
The survey, Lewis said, represents a first step in that process. She cautioned that “we don’t know what the relative importance of these threats to fireflies are. We only know the ranking of what firefly experts believe.”
A contrast in firefly health is evident in the eastern United States. There, Photinus pyralis -- also known as the big dipper firefly, for the dipping J-shape path the beetle makes as it flies — remains a common sight at dusk. “It’s a very weedy species. It’s a habitat generalist,” Lewis said. These fireflies swoop over rural meadows and the streetside gardens of the District. “We’re lucky that we have some fireflies that are probably going to be just fine.”
Due east of the nation’s capital, however, the situation is dire for the Bethany Beach firefly. That insect, which produces bright green double-flashes, lives only in Delaware’s coastal freshwater wetlands. Residential development has imperiled the species, and in May the Center for Biological Diversity and the Xerces Society for Invertebrate Conservation petitioned the Interior Department to add the firefly to the Endangered Species List.
Artificial light at night can confuse the fireflies and glowworms that use bioluminescence for mating rituals. In the United Kingdom, female glowworms climb up to perch at the tips of vegetation and glow to attract males. “A number of different studies have shown that artificial light in a glowworm habitat actually prevents the males from finding the females,” Lewis said.
Background illumination can also mess up the animals’ sense of timing. “I’ve seen fireflies in New York City that begin courting at like 4 in the afternoon in the summertime, which is not the right time,” Lewis said.
In countries such as Japan, Malaysia and the United States — particularly where there are synchronous firefly displays, like the Smoky Mountains — firefly tourism attracts about 200,000 visitors per year, Lewis estimated. Well-meaning tourists may not realize they are endangering the animals they wish to appreciate. “If you have a lot of people who are tromping through the firefly’s habitat, they’re stepping on larvae” or flightless females, she said.
Some places have taken precautions against trampling feet and have developed firefly sanctuaries with elevated footpaths. A recently enlarged firefly preserve in New Canaan, Conn., is the first of its kind in North America, Cratsley said, at least as far as he was aware.
“The land trust was immediately adjacent to a large mansion — a beautiful home,” he said, of his visit in summer 2019. “But you could go from being surrounded by fireflies to a complete dead zone, of nothing, in that manicured lawn.”
The firefly experts encouraged people to join monitoring groups such as Firefly Watch, a citizen-science project run by Mass Audubon that has partnered with Cratsley, Lewis and other researchers.
“If people are willing to spend five or 10 minutes each week out in their backyard figuring out what kind of fireflies they have and then counting their flashes,” Lewis said, “we think we could begin to gather the kind of long-term data that we need to figure out what species are in trouble.”
Where Light Pollution Is Seeping Into the Rural Night Sky (click here)
Submitted by Charlene Uhl
Article appearing in the Washington Post, Dec. 18 2019
By Adrian Higgins Columnist
It is hard to overstate the value and cultural importance of the American chestnut tree for those who came before us.
The native hardwood was once so ubiquitous, it has been said, that a squirrel could travel from Maine to Georgia in the chestnut canopy. The largest trees, spreading 100 feet or more, dropped 10 bushels of nuts, and in the fall the ground was covered with a nut blanket four inches deep, writes sociologist Donald E. Davis in a 2005 paper.
The bears and turkeys feasted, the farmer’s hogs feasted, and the people who lived in chestnut territory feasted — on that sweetened Appalachian ham but also on the economic value of the trees and their nuts. The chestnut’s arrow-straight timber was valued for its size and rot resistance and today endures in the posts and beams of old farmhouses and barns.
For us city folk, the chestnut evokes everything that is nostalgic about yuletide season, the notion of a vendor plying hot roasted chestnuts on a street corner. The aroma, the warmth in the hand, the nutty flavor all conjure one of the more cuddly images of a Dickensian world.
, this diminished holiday custom is carried on with nuts from Asia and Europe, which are bigger but less sweet.
The American chestnut was killed off by the arrival of a blight in 1904 that within a few decades had virtually wiped out an entire, dominant species. In modern parlance the fungus, Cryphonectria parasitica, went viral.
This environmental catastrophe is widely known. Not so broadly understood is that we are closer than ever to returning the American chestnut to its old haunts — or something akin to it. This resurrection has been several decades in the making and has taken two parallel tracks. The first is in the slow, methodical work of traditional hybridization, attempting with each successive generation a tree that will be naturally resistant to the fungus. This has been led by the American Chestnut Foundation, based in Asheville, N.C. The second is by way of genetic modification, undertaken by scientists at the State University of New York in partnership with the foundation. In a world wary of organism-mixing in the lab, this has proved more controversial.
Naturally resistant trees can reach nut-bearing age before the blight knocks them back. This tree is in western North Carolina. (American Chestnut Foundation) The winter garden is full of promise and productivity.
The conventional breeding began by crossing the blight-tolerant Chinese chestnut with some surviving American chestnut individuals that had proved resistant to the fungus, if only to die back to the roots after reaching nut-bearing age.
The foundation was created in 1983 by plant scientists and others who saw the potential of systematic development of a blight-resistant tree through a series of “backcrosses” in which successive generations of American-Chinese hybrids could be bred with resistant American chestnuts. Once these crosses produced trees that were carrying chiefly the American chestnut genome — as much as 90 percent — they were crossed with each other. The challenge has been to select seedlings with enough Chinese blood in them to ward off the disease and yet still look like the American chestnut. At maturity, the American tree is tall and spreading with a thick, straight trunk. The Chinese species is shorter and more branching.
Most of this work goes on at a research station in southwest Virginia named Meadowview Research Farms. The foundation is supported by 5,000 members and chapters in 16 states.
Jared Westbrook, the foundation’s science director, said that of 60,000 seedlings planted and evaluated, 4,000 have made the cut so far. That number will be reduced to 2,000 in the coming months, and a final cut will leave 600 trees by 2021 as the culmination of the breeding program. These will be used to re-populate the Appalachian forest — though earlier-generation trees produced at Meadowview have already been planted on 40 private, state and national sites in the chestnut’s historical range. Westbrook is using a technique called genomic selection to pick the finalists — by analyzing their DNA he can identify individuals with the desired traits.
This is not to be confused with genetic modification, which is the tack employed by William Powell and his colleagues at SUNY’s College of Environmental Science and Forestry. They have used a wheat gene to counter the effects of the disease and have asked the Agriculture Department to sign off on its release. Also, Powell said, the Environmental Protection Agency will decide whether the antifungal properties constitute a fungicide, which would require pesticide registration. In addition, the Food and Drug Administration will determine whether the nuts are safe to eat.
The foundation is working with the researchers. “If it gets through the review process, the American Chestnut Foundation would breed that gene into a diverse population,” Westbrook said. “We are using all the tools available to us.”
The genetically engineered or transgenic chestnut is facing opposition from an alliance of environmental groups named StopGEtrees, which claims its release into the wild would be “a massive and irreversible experiment” and pave the way for other forest tree species to be genetically engineered and released.
“This would be the first one to be released into nature,” said Rachel Smolker, co-author of a report critical of the plan. The restoration of the American chestnut is such an appealing idea that the proponents of genetic engineering are using it to win acceptance of the broader biotechnology, she says. “It’s about winning public support for genetically engineered trees, which has met with tremendous public resistance,” she said. “It’s a very deliberate strategy. A tree engineered for biofuels doesn’t win over the public in the same way.”
Powell says the bacterium he used to carry the wheat gene into the chestnut chromosome is already found, naturally, in the DNA of some tree species, including the walnut. “Walnut is a natural GMO,” he said. The biotechnology “can be applied to other trees,” he says. “But it’s a good thing, it can save more trees.”
This fall, residents of the Lyon Park neighborhood of Arlington County gathered in their community park to plant two non-transgenic saplings from the chestnut foundation to mark Lyon Park’s centennial. They are just a few inches tall, but they are latent giants. “We are protecting them and doing the best we can,” said resident Gray Handley. A hundred years after the demise of the American chestnut, there is hope that future generations will witness something denied ours, the return of the big old American chestnut.
Attached is a paper titled "Biodiversity Loss - The Decline of the North American Avifauna" authored by scientists from Cornell Ornithology Lab, SCBI, and others on the loss of North American birds. It not only documents the extraordinary loss of birds in North America, but also shows important citizen science has been in conducting such research.
Paper Summary: Species extinctions have defined the global biodiversity crisis, but extinction begins with loss in abundance of individuals that can result in compositional and functional changes of ecosystems. Using multiple and independent monitoring networks, the article reports population losses across much of the North American avifauna over 48 years, including once-common species and from most biomes. Integration of range-wide population trajectories and size estimates indicates a net loss approaching 3 billion birds, or 29% of 1970 abundance. A continent-wide weather radar network also reveals a similarly steep decline in biomass passage of migrating birds over a recent 10-year period. This loss of bird abundance signals an urgent need to address threats to avert future avifaunal collapse and associated loss of ecosystem integrity, function, and services.
Link to Science Magazine article
What Can ORMN Members Do?
Cornell Ornithology Lab is encouraging citizen scientists in the month of October to use the eBird application to record bird observations. In particular, October 19th has been designated as the Global Big Day where citizen scientists are asked to use eBird over 24 hours to note the birds observed at their favorite park/county/state/province country/continent (https://ebird.org/octoberbigday). The record to beat is last year’s total of 6,331 species on a single October day.
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