New Paper – Cities: more of the same for people and animals

Say you are on a road trip. You fall asleep, head lodged against the (hopefully passenger side) window. The last thing you see before drifting off is a string of stores: Starbucks, Target, Bed Bath and Beyond, Walmart, Home Depot……Zzzzzzzzz.

You wake up in half an hour, 2 hours, or 3 days, peek your eyes open and think you haven’t moved at all. The same string of stores would be outside your window again and again. Stop to eat in downtown Atlanta, San Antonio, Seattle or any city in between and you have the same experience. A few unique restaurants you never heard of and maybe you can track down some regional specialty but for the most part you have the same foods as in your home city.

Look familiar? GoogleMaps.

This is called ‘urban homogenization’ and animals experience the same problem. Herbivorous insects and pollinators find the same plant species in urban landscapes across the country. Look outside your window. Do you see holly, boxwood, azalea, ligustrum, and cherry laurel shrubs? How about the trees?: red maple, lacebark elm, crape myrtle, crab apple? Since the plant community looks similar so does the community of arthropods that use those plants for food. Bugs that need a ‘regional specialty’ may be excluded from urban ecosystems.

The temperature, soil moisture, and air quality of distant cities are often more similar to each other than each city is to local natural areas. Kevin McCluney, a former postdoc in our lab (now at Bowling Green State University), conducted a study to determine if environmental homogenization among cities led to homogenization in arthropod hydration (or dehydration).

Can you guess which is Orlando, Raleigh, and Phoenix? Photos: Kevin McCluney.

Now, check out how different the natural environments are surrounding these three cities. They are in the same order as above: Raleigh, Phoenix, and Orlando. In the third photo, Kevin McCluney takes measurements outside of Orlando.

In a new paper, Kevin and coauthors report that due to homogenization in plant communities and landscape maintenance practices, like irrigation, that arthropods in a wet city (Orlando) and temperate city (Raleigh) were less hydrated than in adjacent natural areas but arthropods from a dry city (Phoenix) were more hydrated than arthropods from the adjacent desert areas. Thus, arthropods in very different background climates become more physiologically similar in cities.

Arthropod hydration and other physiological traits like heat tolerance affect their survival, plant and prey consumption, activity patterns, and reproduction. Understanding how physiological states change in cities can help predict the fate of species we are trying to conserve and the damage caused by pests to improve urban plant and wildlife management.

Read the full article:

McCluney,K.E., Burdine, J.D., Frank, S.D. (2017) Variation in arthropod hydration across US cities with distinct climate. Journal of Urban Ecology, 3 (1): jux003. doi: 10.1093/jue/jux003

March 3rd, 2017|Categories: Urban Ecology|Tags: , |

Feral honey bees offer tools for managed honey bee health

Honey bee. Photo:SDF

People have domesticated many different plant and animal species to utilize for food, fiber, or other resources. To domesticate a plant or animal people deliberately breed individuals that have valuable or desirable traits – big ears in corn, longer shelf life in vegetables, less fat (unfortunately) in pigs, large, dry flavorless breasts in chickens. The value and desirability of these traits are in the eye of the beholder.

Organisms cannot excel at everything. Breeding to enhance one trait inevitably diminishes another trait. This is called a trade-off and occurs in most domesticated plants and animals. Crops bred for greater yield often have lower resistance to pests and diseases. Animals often have the same problems; bred for rapid growth domestic pigs, chickens, cows often have lower immune function or resistance to disease.

Honey bees have been on the world stage for several years since beekeepers have experienced higher than normal colony losses. Despite all the attention and even affection honey bees have received many people are surprised to learn they are domesticated, exotic, animals just like other livestock. And, as with other domesticated animals, bees have been bred for traits such as honey production, overwinter survival, and easy handling.

A wild honey bee colony lives in the hole in this tree. Photo: SDF

As animals are domesticated the genetic diversity of the population often declines. Genetic diversity can help individuals and populations survive environmental stress and disease. In a new paper, Margarita Lopez-Uribe (former postdoc from the Tarpy, Dunn, and Frank labs now faculty at Penn State) and co-authors compared genetic diversity of feral and managed honey bee colonies. In a previous paper, Elsa Youngsteadt, Holden Appler and others reported that feral honey bees had greater immunocompetence than managed honey bees.

In the new paper, we looked to genetic diversity as a possible mechanism. Feral colonies had less genetic diversity than managed ones. However, transcription of immune related antimicrobial peptides increased as genetic diversity increased in feral colonies but not managed colonies. This suggests that the genetic diversity that does exist in feral bees, perhaps due to natural selection for optimal genotypes and immune variants, improves their immune function. Genetic diversity in managed colonies, from artificial selection for desirable traits, does not improve immune function.

Thus, there may be a trade-off between having bees with traits desirable to beekeepers and bees that can fend off the constant onslaught of diseases to which honey bees are subjected. Scientists and beekeepers are working from every angle to improve honey bee health and sustainability. They should look to feral bees, that survive in the wild without the pesticides and medicines used in managed colonies, for novel genetic variation that could improve disease resistance.

López-Uribe, M.M., Appler, R.H., Youngsteadt, E., Dunn, R.R., Frank, S.D., Tarpy, D.R. (2017) Higher immunocompetence is associated with higher genetic diversity in feral honey bee colonies (Apis mellifera). Conservation Genetics. doi:10.1007/s10592-017-0942-x

This study was funded by the CALS Dean’s Enrichment Grant from North Carolina State University (to DRR, SDF, and RRD) and a National Science Foundation (NSF) Postdoctoral Fellowship (1523817 to MMLU).

February 23rd, 2017|Categories: Pollinators|Tags: |

As spiders leave the kitchen, pests keep cooking

A spider in the family Anyphaenidae has made its home on a twig infested with scale insects.  Photo: Emily Meineke, Harvard University

I think by now most people accept that we can’t hope to preserve all extant creatures over the next 50 or 100 years. Global changes in temperature and habitat will help some species and hurt others, as Elsa Youngsteadt showed in her recent paper. Since we can’t save every creature, what is really important to protect? Increasingly, people try to understand and protect species and ecological interactions that generate ecosystem services for people, rather than diversity per se.

Former undergraduate researcher Anna Holmquist examines branches in the field. Photo: Emily Meineke, Harvard University

Urban warming makes street tree temperatures similar to what is expected under climate change, so we have studied them to predict the effects of warming – urban and global – on pest abundance and tree health. Street trees also host a surprising amount of arthropod diversity if you just look hard enough. In a new paper, our former graduate and undergraduate students, Emily Meineke and Anna Holmquist, with help from Gina Wimp at GWU, studied the effects of warming on spider communities in street tree canopies.

The team tested two predictions. Spiders like to eat and often become more abundant in places where prey is more abundant. So we predicted that, since heat increases herbivore abundance, spider abundance would follow. However, because some spiders probably benefit from warming while others do not, we predicted the composition (member species) of the spider community would be different in hot and cool trees.

The fitness of this spider probably increases with warming since it is hot and sweaty from exercise and yoga. Other spiders (not pictured, you can only work kids so hard) die in, or leave, hot places. Thus, yoga spiders will be more common on hot trees and the community composition will change. Artwork by: I.F.

Ghost spiders, like this one, are nondescript but perform important ecosystem functions. Photo: Matt Bertone, NCSU.

Spiders were by far the most abundant natural enemy group. However, as herbivore abundance increased with warming, spider abundance stayed the same. This is bad news for trees because it means that herbivores can increase unchecked. Instead, urban warming altered spider community structure due in part to a whole family of spiders, Anyphaenids — aptly named ghost spiders – virtually disappearing from the hottest trees in one year of the study. This is bad news for conserving urban biodiversity and also because ghost spiders feed on particular pests like lace bugs.

In this experiment, warming reduced biodiversity but also likely reduces biological control by predators, an important ecosystem service. Something happens in these trees to make a common ecological interaction – predators congregating to prey – stop happening. The consequence is that pests go nuts and trees suffer.

Read the full paper here:
Meineke, E.K., Holmquist, A.J., Wimp, G.M., Frank, S.D. (2017) Changes in spider community composition are associated with urban temperature, not herbivore abundance. Journal of Urban Ecology, 3 (1): juw010. doi: 10.1093/jue/juw010.

January 26th, 2017|Categories: Feature, Natural Enemies, Urban Ecology|Tags: , , , |

Who wins and loses with warming? Where you live matters.

Climate change is generally considered bad for people, earth’s biomes, and, of course, polar bears. But as the climate warms will all critters suffer? Will they all be affected the same way? No. In addition to the losers who slowly fizzle out under the oppressive heat, there will be winners who benefit from warming.

An animal’s response to climate change depends largely on two things: the amount of warming in a habitat and the physiological limits of the animal. It has been shown pretty convincingly that animals closer to the equator are more sensitive to warming than animals farther north. I know what you are thinking, “but tropical animals are hot all the time, they should be used to it.” I thought the same thing, but how it works is that since they are hot all the time, they live close to their thermal limits. So for animals in hot places, a little more heat pushes them over the edge.

Therefore the biological effects of climate change are expected to vary geographically, particularly for ectothermic animals such as insects. Elsa Youngsteadt and other folks in the lab took a road trip to test the hypothesis that insects at high latitudes, where it is cold, should generally benefit from warming whereas insects at low latitudes should have mixed responses: some should benefit, but others should be pushed over their thermal limits.

In a brilliant new paper Elsa reports her findings from this trip. The team sampled insects from street trees in the hottest and coolest parts of four cities–Raleigh, Baltimore, Queens, and Boston–taking advantage of the urban heat island effect as a natural warming experiment.

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Four cities at different latitudes were chosen to study warming effects on insect communities. Background map from the National Biomass and Carbon Dataset.

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One of the authors, Andrew Ernst, takes measurements at a typical study tree. Photo: E.K. Youngsteadt


In the lowest latitude city, Raleigh, some taxa became more abundant with warming while others declined. This suggests that, although some species benefited from warming, just as many species suffered. In the coldest and highest latitude city, Boston, most insect groups were unaffected or became more abundant, suggesting that warming was good for most species living in a frigid northern metropolis. Just as predicted! This doesn’t happen very often.

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Yellow sticky cards were used to sample insect communities in urban trees. Photo: E.K. Youngsteadt.

It seems good that not all taxa tank in Raleigh–but the fact that some benefit and others decline could be ecologically disruptive, too: Maybe a parasitoid and its host respond differently, or a predator and its prey. This sort of mismatch could lead to extinction of higher trophic levels if the prey does poorly, or herbivore outbreaks if the predator fails.

I’ll warn you upfront, this paper is dense and there are probably a lot of new concepts packed in that most people will need time to unpack. However, capturing the response of a whole community to a couple degrees of warming is novel and worth the read. Think about the responses of your favorite organisms. Not just in cities but across the globe.

Read the paper here.

December 16th, 2016|Categories: Urban Ecology|Tags: , , , |

iBook for Greenhouse Pest Identification

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The 2nd Edition of “Insect and Mite Pests of Floriculture Crops: Identification Guide” by Matt Bertone, Steven Frank, and Bryan Whipker is now available from iTunes. This guide is designed so growers, extension personnel, or anyone else can identify common arthropod pests on greenhouse crops.

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This new edition covers aphids, fungus gnats, leafminers, mealybugs, mites, scales, shoreflies, thrips, and whiteflies. Concise biology and management information is paired with galleries of fantastic photographs by Matt Bertone.

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Galleries feature multiple views of the pests, their damage, and their natural enemies. The final edition will be out in 2017. And guess what? Its free so download it now! Thanks to a grant from the Fred C. Gloeckner Foundation.

November 10th, 2016|Categories: Greenhouse IPM|Tags: , , |

New paper: Urban warming reduces aboveground carbon storage

This is a guest post from our former student (now postdoc at Harvard) Emily Meineke.

Through years of studying urban trees and the insects that eat them, we, the Frank lab, have discovered that warming in cities leads to more pests. We also know how: where it’s warmer, insects survive and reproduce better, and the effects of their natural enemies are diminished. In most conversations we have about this work, explaining these discoveries leads to the question: but what does this mean for the trees?

Street trees perform essential services like removing pollutants from air. Photo: EK Meineke

Street trees perform essential services like removing pollutants from air. Photo: EK Meineke

I tackled this question with the help of Elsa Youngsteadt by studying how warming and pests affect tree drought stress and functions like photosynthesis and stomatal conductance. Of course, as in my previous work, I studied the charmless but interesting oak lecanium scale on willow oaks which are among the largest and most common street trees in Southeastern cities.

Oak lecanium scales on willow oak. Photo: EK Meineke

Oak lecanium scales on willow oak. Photo: EK Meineke

Over three years we took hundreds of tedious measurements (thanks Elsa!) to figure out how fast our trees were growing and thus how much carbon they were removing from the air and storing in their tissue. This is called carbon sequestration and is a critical way trees reduce carbon pollution and global warming.

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Elsa measuring photosynthesis. Photo: EK Meineke

In a new paper, we show that the urban heat island effect significantly reduces street tree growth. This is because trees in warmer urban areas photosynthesize less. When these effects were scaled up to all the willow oak street trees in Raleigh, warming reduced citywide carbon sequestration by 12%. However, insect pests like scales and spider mites had minor effects on tree growth compared to warming, at least in the short term.

Oak spider mites damage leaf cells and reduce photosynthesis. Photo: EK Meineke

Oak spider mites damage leaf cells and reduce photosynthesis. Photo: EK Meineke and A Ernst

These results lead to several recommendations for urban forest management. First, because urban and global warming are becoming more intense, urban trees will store even less carbon in the future. However, managers may be able to reduce these effects by planting trees that are more tolerant of hot urban conditions. This highlights the need for research to identify what trees are appropriate to plant in hot urban environments. In general, this research makes us excited about science that will help landscape designers tailor green infrastructure for resilience to climate change and intensifying urbanization.

Our results also highlight the utility of cities as large-scale natural climate experiments, in which sessile organisms, such as trees and many insect herbivores, are confined to different thermal environments in close proximity. The range of urban warming they experience parallels the extent of global warming expected regionally, outside the city, over the next several decades. Therefore, cities can serve as experiments that allow scientists to address questions that are otherwise difficult or impossible to approach, such as the effects of warming on mature trees.

Meineke, E.K., Youngsteadt, E.K., Dunn, R.R., Frank, S.D. (2016) Urban warming reduces aboveground carbon storage. Proceedings of the Royal Society – B 283: 20161574 DOI: 10.1098/rspb.2016.1574

October 7th, 2016|Categories: Urban Ecology|Tags: , , , , |

Bees and army bands: The remarkable life of TB Mitchell

This is a guest post from our Research Associate, Elsa Youngsteadt

T. Mitchell

A portrait of T.B. Mitchell in the lab. Image courtesy of Special Collections Research Center, North Carolina State University Libraries; photographer unknown.

T.B. Mitchell is probably the reason we ecologists in eastern North America can identify our bees. Mitchell joined the faculty here at NC State in 1925 and distinguished himself as a meticulous taxonomist.

Although he died in 1983, more than 30,000 of his bee specimens are housed here in the NC State Insect Museum, where one can occasionally feel a little time warp: The specimen I am examining right now, under the microscope, was alive in 1925. It was cruising from flower to flower along some North Carolina country roadside 91 years ago when Mitchell nabbed it with his net. He pinned it, identified it, labeled it, may have studied it while writing the key I’m now using—and I’m handling that exact bee, comparing it to one of the same species that I caught last week.

Enough of this kind of thing, and you wish you could meet the guy who made the collection. Thanks to lab alum April Hamblin’s idea to propose a Heritage column for American Entomologist, we nearly feel that we have. April, Margarita López-Uribe, Heather Moylett, and I spent the better part of a year, off and on, going through boxes of letters and stacks of theses, reading Mitchell’s papers, and conducting interviews and correspondence—including actual paper letters. The resulting article is published in the fall 2016 American Entomologist. We invite you to read it and get acquainted with this energetic, unflappable gentleman, his scientific contributions, and his remarkable experiences as a musician and entomologist.

August 30th, 2016|Categories: Lab Happenings, Natural History and Scientific Adventures, Pollinators|Tags: |

Impervious surface cover is bad for trees. How much is too much?

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Gloomy scales on red maple. Photo: AG Dale

We have studied the effects of urban warming and other factors on tree pests and tree health for several years. The gist of it is impervious surfaces increase plant stress by warming the atmosphere and reducing water availability. Adam Dale and Elsa Youngsteadt studied the effects of impervious surface cover on red maples to determine how much is too much? In a new paper they answer this question to create an impervious surface threshold that planners and planters can use to determine if sites are suitable for red maples. Their analyses of impervious surface cover and red maple condition in Raleigh, NC indicate that red maple condition is most likely to be excellent or good if impervious surface cover is less that 32% within a 25m radius. At 33% to 66% impervious surface cover, trees were most likely to be in fair condition. Above 66% impervious surface cover, trees were mostly in poor condition.

 

Good to know but how do you measure impervious surface cover? Not many landscapers are going to pull up satelite images on their phones and bust out ArcGIS to measure the amount of impervious surface around a tree. Instead we came up with the Pace to Plant technique. With this technique anyone can acurrately measure impervious surface cover at 25 m radius just by pacing transects and counting the steps that fall on impervious surfaces.

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With an impervious surface threshold in hand hopefully landscape architects and other planners will not specify red maples on plans when impervious surface cover is high. Tree care professionals on the ground will also be able to assess if a planting site is suitable for red maples. Two small (even medium) steps for urban tree IPM.

May 17th, 2016|Categories: Landscape IPM, Urban Ecology|Tags: , , , |

Do urban bees eat more junk food than rural bees?

Photo Jun 20, 10 56 06 AMUrban animals eat all kinds of things they would never eat in a ‘natural habitat’. Urban ants eat lots of foods left behind by people on the ground and in garbage bins. Clint Penick from the Dunn Lab recently published a paper showing that some ant species eat more processed human foods in highly urban traffic islands than in parks. Using a similar technique Clint, Cat Crofton, an undergraduate in our lab, and a team of others investigated if city honey bees also eat more soda and sweets than rural bees for lack of flowers. In turns out they don’t. In their new paper Clint and Cat show that honey bees managed by bee keepers consume more cane or corn derived sugar than feral bees because bee keepers provide supplemental sugar to their hives. Feral bees, those living in trees or other places and not managed by people, consume less cane or corn sugar than managed bees. They also seem to find enough flowers and other natural food sources in cities and don’t have to resort to human foods. Good news for bees and picnickers.

May 17th, 2016|Categories: Pollinators, Urban Ecology|Tags: |

Urban environments increase pathogen pressure on honey bees

bee2_elsa1Our lab’s latest paper, co-authored by Elsa Youngsteadt and Holden Appler, was published today in PLOS ONE. We examined pathogen pressure and immune response in managed and feral honey bee workers from hives located in urban* and non-urban environments. We found some very interesting results, and as science usually goes, we now have a lot more questions.

The urban bees we examined in the study, regardless of whether they were feral or managed, had higher levels of the fungal pathogen Nosema ceranae and Black Queen Cell Virus. We also tested the survival of urban bees in the lab and compared it to their more rural neighbors. Survival for bees in the most urban environments was three times lower than for those in the most rural environments.

Given the stress factors that urban settings present to foraging bees (such as pollution and higher temps), it’s easy to imagine that a compromised immune system in the urbanites might be the culprit. Kinda like when you get super stressed and stay up all night cramming for that big exam (or partying) and find yourself with a cold a few days later. But, our data didn’t support this idea; we didn’t observe a stronger immune response in rural bees relative to urban bees. Something else seems to be contributing to the higher pathogen pressures we saw in the urban bees.

We hypothesized that that ‘something else’ could be urban factors working in favor of the pathogens, making them more abundant or easier to transmit between honey bee workers from different hives. Higher frequency of worker visits at scarce urban food sources could increase the likelihood that bees will pick up diseases from their environment (think the public water fountain or the notorious buffet line). The fungal pathogen in question, N. ceranae, has also been shown to benefit from the warmer temps we see in cities.

This study sets the stage for so many more questions. If urban environments indeed enhance pathogen survival and change the way diseases spread through honey bee populations, is this a red flag for native bee species that share floral and other resources in these cramped urban landscapes? Is urbanization harming them too? Could pathogens jump from honey bees to native bees because they are more abundant or doing better in the city environment? April Hamblin and Margarita López-Uribe are looking into some of these questions and trying to tease out the effects urban living has on our neighborhood native bees.

Check out the paper for some more interesting findings not covered here, and stay tuned for more to come in the native bee department.

*the level of “urban-ness” for each hive was determined using the amount of impermeable surface (concrete, pavement, etc.) in the typical radius a worker bee flies from the hive, 1500 m.

November 4th, 2015|Categories: Lab Happenings, Pollinators|Tags: , , |