ORLANDO, Fla. — Here’s another reason not to love car exhaust: The fumes may make it harder for honeybees to learn floral scents.
In lab tests, bees normally caught on quickly that a puff of floral scent meant a researcher would soon offer them a taste of sugar, Ryan James Leonard of the University of Sydney said September 30 at the International Congress of Entomology. After two sequences of puff-then-sugar, just a whiff of fragrance typically made the bees stick out their tongues. But when that floral scent was mixed with vehicle exhaust, it took the bees several more run-throughs to respond to the puff signal. Honeybees buzzing among roadside flowers must contend with vehicle pollution as they learn various foraging cues. Another lab reported in 2013 that diesel exhaust reacted with some of the chemical components of canola flowers, rendering them more difficult for bees to recognize.
Building on that concern, Leonard and colleagues found that it was easy for bees to learn the scent of linalool, a widespread ingredient in many flower fragrances, whether mixed with exhaust fumes or not. But exhaust made it take longer than two trials for bees to learn the scent ingredients myrcene (three trials), dipentene (four) and the full, multicomponent fragrance of geraniums (six).
Road ecologists have put a lot of effort into studying how vehicles kill animals. But Leonard hopes for more interest now in how chronic exposure to traffic affects living animals.
In crested penguin families, moms heavily favor offspring No. 2 from the start, and a new analysis proposes why. The six or seven species of crested (Eudyptes) penguins practice the most extreme egg favoritism known among birds, says Glenn Crossin of Dalhousie University in Halifax, Canada.
Females that lay two eggs produce a runty first egg weighing 18 to 57 percent less than the second, with some of the greatest mismatches among erect-crested and macaroni penguins. Some Eudyptes species don’t even incubate the first egg; royal penguins occasionally push it out of the nest entirely. Biologists have proposed benefits for the unusual behavior: A sacrificial first egg might mark a claim to a nesting spot or improve chances of one chick surviving predators. But those ideas haven’t held up, Crossin says. He and Tony Williams of Simon Fraser University in Burnaby, Canada, propose in the Oct. 12 Proceedings of the Royal Society B that egg favoritism is just a downside of an open-water, migratory lifestyle. Among the 16 penguin species that lay two eggs, only the Eudyptes species evolved what’s called a pelagic life, spending their nonbreeding season mostly at sea and migrating, in some cases considerable distances, to breeding sites.
Female crested penguins tend to lay their first eggs soon after arriving at a breeding site, meaning that the egg must have started its roughly 16-day development while mom was migrating. The biology of long swims, now encoded genetically, interferes with producing a full-sized egg. A puny first egg might just be a sign that mom is trying to do two things at once, Crossin says.
PORTLAND, Ore. — Petals of wildflowers called starry campions may be a pretty little battleground for a sexual skirmish between the plant’s male and female parts.
As is common in flowers, each Silene stellata bloom forms both male and female sex organs. After measuring petal variation between plants and tracking parenthood of seeds, Juannan Zhou suspected a sexual tug-of-war.
Flowers with greater male success in spreading pollen and siring seeds across a flower patch tended toward longer and narrower petals, Zhou reported June 26 at the Evolution 2017 meeting. Yet flowers that did especially well by their female organs, maturing abundant seeds in their own ovaries, tended toward wider and shorter petals. Zhou, of the University of Maryland in College Park, pieced together the story while working in a fenced-in plot of wild campions at Mountain Lake Biological Station in southwestern Virginia. During two summers, he tracked floral details and collected seeds. He sprouted almost 2,400 seedlings and for each genetically worked out which of 227 fenced-in adults had been the father.
If a conflict smolders between what’s best for male versus female functions, parental blossom trends that went along with greater fatherhood should tilt in the opposite direction from blossom trends linked with greater motherhood. Some traits such as number of fringe tassels showed no signs of conflict, but petal dimensions did.
Zhou suggests that the contrary trends might arise from the sexes’ opposite interests in visits from one of its pollinating moths, the mottled gray-brown Hadena ectypa. These moths do much of the pollen carrying early in midsummer. One mothload of pollen typically fertilizes all the eggs a female has, so from the motherhood perspective, once is enough. More than once means more risk for little benefit, because female moths leave an unwanted gift behind.
Besides sucking nectar, a H. ectypa often sticks her rear into the cup of a flower and with a wiggle, lays an egg or two. When eggs hatch, the tiny caterpillars chew their way into the flower ovary and start feeding on the plant’s own seeds. Caterpillars eventually grow too long and fat to fit inside blooms. Certain petal shapes, Zhou speculates, might be more attractive to moths, or perhaps more discouraging for the fattest, most destructive caterpillars to invade.
From the male point of view, the loss of the home flower’s seeds could be more than recouped by repeated moth visits to pick up more pollen to spread to other flowers. More moths could mean many more offspring. Sexual conflicts show up elsewhere in nature, such as in the compounds that fruit flies use to dope their sperm. After a jolt of these extras, females tend to put more resources into eggs and offspring. Never mind that it shortens a female’s life. Data on sexual conflicts from plants are much rarer, says evolutionary ecologist Locke Rowe of the University of Toronto. He welcomes the starry campion work also because the plants are hermaphrodites, a lifestyle uncommon in conflict studies.
People and pooches may have struck up a lasting friendship after just one try, a new genetic study suggests.
New data from ancient dogs indicates that dogs became distinct from wolves between 20,000 and 40,000 years ago, researchers report July 18 in Nature Communications. Dogs then formed genetically distinct eastern and western groups 17,000 to 24,000 years ago, the researchers calculate. That timing and other genetic data point to dogs being domesticated just once.
That idea contrasts with a hypothesis put forward last year that dogs were domesticated separately in Europe and East Asia, with the Asian dogs eventually replacing the European mutts (SN: 7/9/16, p. 15). Scientists agree that dogs stem from wolves, but where, when and how many times dogs were domesticated — passing down tameness and other traits over generations — has been rethought many times in the last few years (SN: 7/8/17, p. 20).
The new study “puts dog origins into one time and place again. That’s really important,” says Peter Savolainen, an evolutionary geneticist at KTH Royal Institute of Technology in Stockholm who was not involved in either study. These new data indicate “there’s a single origin, and it wasn’t in Europe,” says Savolainen, a proponent of an East Asian origin of dogs.
The new study examined the complete genetic blueprints, or genome, from a 7,000-year-old dog from Herxheim in Germany, and a 4,700-year-old dog from Cherry Tree Cave (also known as Kirshbaumhöle) in Germany. The scientists also analyzed DNA data from a 4,800-year-old dog from Newgrange, Ireland, that had been described in the previous study positing two domestication events. A claim of multiple domestications for dogs requires extraordinary evidence, says study coauthor Krishna Veeramah, an evolutionary geneticist at Stony Brook University in New York. But complete genomes of the ancient dogs suggest a simpler story. “We can explain all of our data just using one domestication event,” Veeramah says. Although Veeramah and colleagues see a split between eastern and western dogs, that split probably happened after domestication took place. Modern European dogs still share heritage with Stone Age canines on the continent, hinting that all the pups came from a common source rather than separately domesticated Asian dogs replacing their European counterparts.
These new data don’t completely rule out multiple domestications (the single event is just the simpler explanation), nor do they indicate where humans and canines became BFFs, Veeramah says. A family tree constructed from the DNA data puts today’s Southeast Asian breeds on the earliest branch, implying an origin in Asia. But a dog breed’s present-day location may not reflect where dogs were actually domesticated more than 20,000 years ago, Veeramah says.
The team that proposed double domestication is not convinced of a single origin. The new study is based on genetic data alone and doesn’t take archaeological evidence into account, says Greger Larson, an evolutionary geneticist at the University of Oxford.
“There’s no smoking gun here, and there’s no direct contradiction,” says Larson. “Our hypothesis of a dual origin remains a possibility, as does a single origin.” Researchers won’t know for sure until they’ve analyzed older dogs from multiple places.
The ancient doggy data also challenge a recently proposed idea that dogs were domesticated when early mongrels developed the ability to digest starch better than wolves could (SN Online: 1/23/13), allowing them to eat grains in early farmers’ trash heaps. A previous study found that today’s dogs have many copies of the AMY2B gene, which produces an enzyme that helps break down starch, while wolves have only two copies.
The new study finds that both ancient German dogs had two copies of AMY2B, while the Newgrange dog had three. Since those dogs lived thousands of years after domestication, the findings suggest the first domesticated dogs were no better equipped to digest starch than wolves were. But the ancient dogs do have other genetic variants that made it possible for the amylase gene to be copied later, Veeramah says. Exactly when that happened isn’t clear.
Craft brewers are going wild. Some of the trendiest beers on the market are intentionally brewed to be sour and funky. One of the hottest new ingredients in the beverages: Yeast scavenged from nature.
Unlike today’s usual brewing, which typically relies on carefully cultivated ale or lager yeast and rejects outsider microbes, some brewers are returning to beer’s roots. Those beginnings go back thousands of years and for most of that time, the microbes fermenting grain into alcohol were probably wild yeast and bacteria that fell into the brew. Now local microbes — in some cases with the help of scientists — are being welcomed back into breweries.
Wild and sour beers are a niche, but growing segment of the craft brewing market, says Bart Watson, chief economist of the Brewers Association. Last year, more than 245,000 cases of wild and sour beers were sold and sales are up 9 percent so far this year.
For geneticist Maitreya Dunham, wild, funky and sour beers aren’t just a market trend; they are ecological microcosms. Dunham’s lab group at the University of Washington in Seattle uses yeast to study genetic variation and evolution. She got interested in beer when her husband took up home brewing. In the bottom of his five-gallon fermentation bucket, the yeast formed a thick mat that bubbled rapidly. “That’s not how we grow yeast in the lab,” Dunham said. She wanted to test a new technique her lab had developed to identify wild yeast in their natural habitat. And what better habitat to explore than a barrel of beer? Dunham teamed up with a brewer who made a wild beer with microbes from a warehouse. “Whatever is living in the old warehouse ended up in the beer,” she says. On a lab outing to the brewery, Dunham and her team took samples from beer barrels, marveling at the thriving mass of microbes gurgling inside. “You could see it being alive in there.” DNA tests revealed that four kinds of bacteria and four kinds of yeast, including a newly identified hybrid yeast, lived in the wild brew, Dunham and colleagues reported June 15 on bioRxiv.org. The hybrid doesn’t have a name yet, because Dunham is still trying to identify its parents. One is Pichia membranifaciens, but the other is an unknown fungus P. membranifaciens is a food spoiler, and no lightweight: It can handle up to 11 percent alcohol. The other parent’s identity and attributes aren’t known, and that ID can take time. People have known for a long time that lager yeast Saccharomyces pastorianus is a hybrid, but scientists didn’t identify both of its parents until 2011.
As excited as Dunham is to find a hybrid yeast, she’s not sure that it will take beer brewing by storm. Her lab brewed a small batch of “science beer” with the hybrid yeast. The yeast didn’t make much ethanol or other flavor compounds. “It didn’t do much on its own,” she laments. But she hasn’t given up hope. Sometimes a yeast needs bacteria or other fungi to really shine. Maybe, she says, “when it’s mixed in with all its friends, it may bring something interesting to the party.”
A Facebook group of home brewers called Milk the Funk is about to help her find out. People from the group saw Dunham’s study on bioRxiv.org and volunteered to ferment beers with and without the hybrid. “I’m about to have a couple dozen people doing experiments for me,” Dunham says. “In fact, they’re going to send me free beer, although it may be weird beer.” (“Funk is one of the flavors they go for in these weirdo beers,” Dunham explains. Descriptions of funk encompass barnyard tastes and smells such as goat, horse blanket, urine, sweat, cheese and manure, as well as spicy notes and complex flavors of clove, smoke, Band-Aid, bacon and bitter, says fellow scientist and yeast hunter Matthew Bochman. “Funk basically covers anything ‘weird’ in beer that might be interesting or pleasant in small amounts but off-putting at higher concentrations.”) Bochman, a biochemist at Indiana University Bloomington and a self-professed yeast whisperer, is also bagging new kinds of wild yeast. Bochman, who studies how cells keep their DNA intact, was a home brewer for years before moving to Indiana. He soon made friends with many local craft brewers there. In 2014, he met brewer Robert Caputo, who wanted to make an all-Indiana beer. There were farmers in the state growing hops and malt grains. Indiana water was plentiful. “The missing ingredient was the Indiana yeast,” Bochman says. Caputo asked Bochman to help him find the missing microbe. “So we went yeast hunting.”
That spring and summer, Bochman collected about 100 strains of yeast. “Whenever I was out and about I would grab something — a piece of a bark, a berry — bring it back to the lab and get yeast from it.” The microbes are everywhere, he says. “It’s hard not to find yeast.”
But not just any yeast will do. For beer brewing, he needed to find yeast that eat the sugar maltose in the wort — the liquid extracted from grain mash that will be fermented into beer. Yeasts used for brewing also have to be tolerant of hops, which make weak acids that might slow yeast growth. The yeast must be able to live in 4 to 5 percent alcohol. In addition, the microbes have “to smell and taste at least neutral, if not good,” Bochman said.
Not all yeast can pass the sniff test. For instance, eight strains of Saccharomyces paradoxus “all smelled and tasted heavily of adhesive bandages,” Bochman and colleagues reported August 7 on bioRxiv.org.
But in 2015, a batch of wild beer brewed in an open vat in a vacant lot in Indianapolis by Bochman’s friends at Black Acre Brewing Co., yielded a winner. Among the four species and six strains of yeast in the beer was a Saccharomyces cerevisiae strain called YH166. S. cerevisiae is the species of yeast used to brew ales and wine and to make bread. YH166 lends beer an aroma that is “an amazing pineapple, guava something. Like an umbrella drink,” says Bochman.
He doesn’t yet know what chemicals the yeast makes to produce the tropical fruit scent. He puts his money on one of the sweet-smelling esters yeast use to attract the fruit flies that can give the fungi a lift — sort of a microbial version of a ride-hailing app. Sour beer brewers may also benefit from Bochman’s bio-prospecting. Sour beers generally contain lactic acid bacteria in addition to yeast. Brewers need separate equipment for brewing sour beers, because it’s difficult to get rid of all the bacteria in order to brew a nonsour beer. Among 54 species of yeasts Bochman and colleagues investigated, he found five strains that can make both alcohol and lactic acid to brew sour beers without troublesome bacteria. The researchers described the five sourpusses — Hanseniaspora vineae, Lachancea fermentati, Lachancea thermotolerans, Schizosaccharomyces japonicus and Wickerhamomyces anomalus — July 28 on bioRxiv.org. Bochman and Caputo formed Wild Pitch Yeast, a company to sell the strains, in part, to fund his yeast research. The company supplied yeasts isolated from cobwebs, trees and other spots to brewers for making all-Indiana beers, dubbed “Bicentenni-ales” in honor of the state’s 200th anniversary.
Both Bochman and Dunham are relying on brewers to tell them how their newfound yeast perform in the real world. “The proof is in the brewing,” Bochman says. “You can do as many lab tests as you want, but you’re never going to know how something will act until you throw it into some wort and let it bubble away for a couple of weeks.”
Vaping e-cigarettes with high amounts of nicotine appears to impact how often and how heavily teens smoke and vape in the future, a new study finds.
In 2016, an estimated 11 percent of U.S. high school students used e-cigarettes. Past research has found that that teen vaping can lead to smoking (SN: 9/19/15, p. 14). The new study, published online October 23 in JAMA Pediatrics, is the first look at whether vaping higher amounts of nicotine is associated with more frequent and more intense vaping and cigarette use in the future. Researchers at the University of Southern California surveyed 181 10th-graders from 10 high schools in the Los Angeles area who had reported vaping in the previous 30 days, then followed up six months later, when the students were 11th-graders. The teens answered questions about how much and how often they had smoked and vaped in the past 30 days and about the amount of nicotine in their vaping liquid. The researchers categorized the amount of nicotine as none, low (up to 5 milligrams per milliliter), medium (6 to 17 mg/mL) or high (18 mg/mL or more).
With each step up in nicotine concentration, teens were about twice as likely to report frequent smoking versus no smoking at the six-month follow-up. Teens who vaped a high-nicotine liquid smoked seven times as many cigarettes per day as those who vaped without nicotine.
Also with each nicotine level increase, teens were about 1½ times as likely to report frequent vaping than no vaping at all. Vaping high-nicotine liquid led to almost 2½ times as many episodes of vaping per day compared with no-nicotine vaping, and kids took more puffs each time they vaped.
“This study is important because it begins to chip away at the ‘black box’ that links e-cigarette use with later use of regular cigarettes,” says sociologist Richard Miech of the University of Michigan in Ann Arbor. “Ideally, studies like this will encourage government agencies to develop policies that will make it very difficult for youth to obtain e-liquids with nicotine.” In 2016, then-U.S. Surgeon General Vivek Murthy released a report on e-cigarettes, concluding that using nicotine-containing products in any form is not safe for youth. Studies find an association between nicotine use in teens and problems with learning, attention and impulse control, as well as addiction (SN: 7/11/15, p. 18).
