Fun fact: there are LOTS of native bee species in urban areas!! Preliminary results of a study that hasn’t been published yet compared rare bee diversity in agricultural, urban, and forested settings – and interestingly, urban settings won out a good portion of the time! Why? We’ll have to wait and find out when her publications come out. But an initial hypothesis of mine is that urban landscapes offer lots of structural complexity where bees can create nests, and that people plant lots of diverse flowers in their window boxes, gardens, and landscaped areas.
Join moderator Timothy Beatley, professor at the University of Virginia and founder of the Biophilic Cities Network, Gary Krupnick, conservation biologist at the National Museum of Natural History, Catherine Werner, sustainability director for the City of St. Louis, and other experts for a discussion about projects that are benefiting both people and pollinators in urban environments.
Learn about successful projects such as St. Louis’s “Milkweed for Monarchs” initiative, as well as Smithsonian research, including the National Museum of Natural History’s Pollinator Garden. Participants will discuss government and grassroots recommendations for sustaining healthy pollinator populations.”
Feature image is the same one on the event web page and was taken by Katja Shulz, Smithsonian.
In a somewhat unprecedented move, Benjamin Santer and colleagues have published a paper reiterating the scientific consensus regarding tropospheric warming over the past two decades in order to refute recent claims by EPA Administrator Scott Pruitt that warming has “leveled off.” Read the article here:
After a long respite on this blog due to limited access to a computer while my laptop was being fixed, I’m happy to make the belated announcement that I’ll be joining the Population Biology graduate group as a first-year PhD student at UC Davis in Fall 2017!
My primary advisor will be Jennifer Gremer, a new plant ecologist in the Evolution and Ecology department. I’ve been working closely with her during my time as a Research Assistant in Johanna Schmitt’s lab, the position I currently hold, because she is co-leading a project that takes up the majority of my responsibilities as a tech.
I’m even thinking about doing some of my own PhD research on the project I’ve been working on for the past year – we are studying life history variation and local adaptation in the native California wildflower Streptanthus tortuosus in the context of its potential ability to adapt to climate change.
S. tortuosus is an ideal study organism for these questions because it displays a wide range of morphologies and adaptations across its range, which encompasses most of California and elevations from about 500-12,000 feet. It’s also classified as a biennial or perennial in many field guides, but we’ve seen it display an annual life history as well. In fact, we think we’ve found a trend in life history: increasing perenniality with increasing elevation. It also responds differently to vernalization treatments, flowers at different times, and grows at different rates in a common garden, providing some evidence for genetic differences in these traits.
I am especially interested in finding out whether this species is locally adapted to snowmelt timing on mountainsides. I have tentative plans to explore this question further this summer at Lassen Volcanic National Park, where I have observed plants displaying very different phenologies dependent on snowmelt timing across very short physical distances. These plants are bad at selfing, which means they rely on outcrossing by pollinators to reproduce, so I also want to study the landscape genetics of the species at Lassen – are there different “genetic cohorts” reproducing with each other every year because they consistently have open flowers at the same time as a consequence of when they emerge from the snow?
Hopefully, I can equip myself with the conceptual, statistical, and methodological tools to begin answering these questions during my first year of classwork as a PhD student. Whether or not this ends up being my dissertation project, I’m learning a lot about plants, genetics, and conducting long-term independent research in the meantime!
Honey bees get a lot of attention from the media because they help to pollinate the food we eat, but in terms of their conservation, agriculture is really the only reason we would focus on protecting honey bees. They are actually a non-native species from Europe, are not in any danger of dying out as a species, and in the wild, they often outcompete native bee species for floral resources, potentially causing harm to ecosystems overall. The following paper is about native or naturalized bumblebee species and describes one of the problems native bees are facing in nature due to climate change. Read on to learn more!
In this paper, the authors are focusing on bee and plant phenology, which is the timing of life events like birth, death, and peak activity, and in plants specifically, events like sprouting, budding, flowering, fruiting, and senescing (pre-programmed partial or complete death of plant parts, like when oak trees shed their leaves in the fall). Bees and plants interact with each other in a mutualistic relationship, meaning they help each other out with functions necessary to survival. This occurs primarily through pollination, whereby bees collect nectar and pollen to eat and feed their young, and the plants receive fertilization so they can produce successful offspring. But this mutualism can only occur when the bees and plants are operating on the same timeline – bees need to be buzzing around searching for food at the right time of the season, namely, when flowers are open on plants, for pollination to proceed. With changes in climate, bees and plants may need to shift their phenologies to coincide with optimal weather conditions – but a big question in ecology right now is, will they shift their phenologies in the same way so that they stay matched up with each other? This potential phenological mismatch between bees and plants, or asynchrony, is what Pyke and his colleagues explore in this paper.
Organisms are expected to respond to changing climate by shifting geographical ranges and phenology toward remaining in their compatible climate zones
Such changes may result in spatial or temporal mismatches between interacting species (asynchrony)
This study examines mismatches arising from climate-induced shifts in plants and their pollinators
Surveyed bumble bees and the plants they visit in 1974 and 2007 at the Rocky Mountain Biological Laboratory in Colorado (33 years)
Tested hypotheses arising from observed climate change
The Rocky Mountain Biological Laboratory (RMBL) has been providing scientists with a natural outdoor laboratory since 1928. Many famous studies have been conducted there, and an author on the paper, David Inouye (below), has spent summers performing experiments on pollination ecology at RMBL since 1971.
RMBL is a great place to study shifts in phenology due to climate change, because changes in temperature occur very rapidly with changes in altitude on the slopes of mountains. In the 33-year intervening period between their two study years, for example, monthly spring and summer temperatures have increased 2 degrees C on average, which means that for plants and bees to experience the same temperature conditions they had in 1974, they must move 317 meters up the mountain by 2007.
H1: Species distributions have shifted upwards by about 317 m to match the change in temperature with elevation
H2: Phenologies have shifted earlier in the season, but not identically, resulting in asynchrony (mismatching)
H3: Bumble bee abundance was lower in 2007 than in 1974 (due to asynchrony)
Study encompassed an elevation range of 1000 m and spatial range of 16 km
47 study sites – dominated by grasses and herbaceous plants
Surveyed every 8 days (1974) or 6 days (2007)
Transects or “circle sites” (covering circular areas on roadsides)
ID’d bumble bees observed and flowers visited
12 perennial plant species ID’d as important to bumble bees (represented 74.5% of visits)
8 bumblebee species (represented 97% of bumble bees observed)
Did bees shift up?
H1A: Bees shifted up but not necessarily 317 m
Did plants shift up?
H1B: Plant species did not show significant change in upwards distribution (expect one species)
Did bee phenology shift earlier?
H2A: Phenological differences were partially consistent with hypotheses
Workers shifted in peak recording rate ~17 days earlier in transect sites
Did flowering phenology shift earlier?
H2B: Flowering phenology was significantly earlier in 2007 compared with 1974
Was there asynchrony (mismatching) between bees and plants?
H2C: Found expected reduction in synchrony between bees & plants
However, the authors assume that the bees and plants were synchronous in the first place in 1974
Was there lower bee abundance in 2007?
H3: Found lower bee abundance in 2007 compared with 1974
Backyard Bumblebee on Coneflower (Head-On)
Summary of results
Shifts towards higher elevations for most bumble bee species, but not for most plant species
Phenology shifted earlier for plants but not bees
Bees and plants were mismatched in 2007
Bee abundance was lower in 2007
We discussed this paper in a seminar on the phenological consequences of climate change that I’m auditing this quarter at UC Davis. Here are some of the points our discussion centered around:
Only 2 years of data – are their conclusions justified?
Why are upward shifts in bees inconsistent with the expectation (317 m)?
Their surveys in 2007 ended before bumble bee workers declined, making it difficult to accurately estimate dates for peak recording rates – how might this affect their results?
Can’t draw a causal link between reduced synchrony & reduced bee abundance, but how convinced are we that they’re related?
Could not support the hypothesis that phenologies coincided seasonally in 1974 but not 2007 – do we think this reduces the power of their results?
How can we better incorporate both spatial and temporal changes due to climate change when considering mismatch, especially for mutualisms occurring on steep environmental gradients?
Particularly if you read the paper in full, I encourage you to think carefully about these potential issues with the paper. It took me six years of reading scientific papers to feel comfortable with questioning methods, statistics, results, and claims that authors make, but learning to approach science with a healthy degree of skepticism is an important part of the your development as a critical thinker and the scientific process as a whole and. Always remember that correlation does not imply causation, and that each paper is only a small part of the bigger picture that science will eventually paint on particular issues as evidence builds over time. Certain parts will inevitably be wrong, and it’s our job as researchers to figure out which bits are wrong, and which bits are right, so we can eventually discover the mechanisms and processes that drive natural phenomena over the long term.
Regardless of the potential problems with the paper, I found it most interesting because while phenological mismatch is a hot topic to study in ecology right now, this is the first paper I’ve seen that studies several bumble bee species and several plant species at once, or the whole plant-pollinator community occurring in the study area. It is also the only paper I’ve come across that considers both the temporal and spatial components of mismatch: it’s easier to quantify phenology in ecological studies, so the temporal component has been overstudied in comparison to the spatial component, but both are equally important – think about it, if the bees and plants aren’t in the same physical location, it will be harder for pollination to proceed normally.
Why should you care?
Mismatch between all different kinds of interacting species around the world can have potentially devastating consequences for ecosystem functioning, and in turn, the provisioning of ecosystem services to humans. Nature consists of highly interconnected systems where organisms interact both directly and indirectly with each other in tandem: take the famous example of wolves having cascading effects on the ecosystems in Yellowstone National Park. When wolves were reintroduced, deer began avoiding parts of the park, which allowed plants to grow back. Willow and aspen trees sprang up, and with them came more berries and insects, attracting more bird species to the park. Beavers came back and created dams with wood from the trees, and the dams attracted otters, muskrats, and other reptiles. Wolves also killed coyotes, so the mice and rabbit population grew, attracting weasels, red foxes, badgers, and hawks. The wolves even indirectly changed the rivers — with increased plant growth now that deer were not munching everything in sight, the vegetation decreased erosion and stabilized river banks. Channels narrowed, more pools formed, and the rivers stayed more fixed in their course. In this ecosystem, everything is functioning properly and imposing balance on its individual components. But what if the timing was all off? What if the deer were giving birth before the plants started to grow in the spring time and the babies didn’t have enough food to survive? What if the berries didn’t grow on the trees at the same time as birds were foraging for food? What if the deer moved to a climate they preferred because the climate was warming, but the wolves didn’t move as quickly and the deer started to eat all the vegetation again because their populations weren’t being held in check by predators? These are the kinds of questions ecologists are asking about phenological mismatch due to climate change, and finding the answers will be of paramount importance in understanding how to conserve nature and protect intact ecosystems.
In this paper, the authors explore how seeds sprouting early versus sprouting late in the season can be good or bad for the plant’s overall fitness (its ability to survive and reproduce) depending on the effect that sprouting time has on the plant’s fitness at different stages in its life cycle.
To understand what they’re studying, it is important to know what “conflicting selection” is. First, plain old selection is the process by which more adapted individuals (i.e., those with better fitness) survive and pass on their genetic information to the next generation. Many many instances of natural selection over time cause evolution to occur.
Conflicting selection is a slightly more complicated version of regular selection. Jose Gomez (2004) describes a basic example in which producing bigger acorns can be advantageous for an oak plant to make because they contain more nutrients for the sprouting plant to use, but they can also be disadvantageous because animals that eat acorns, like squirrels, prefer to collect larger acorns. In cases like this, you might expect that because the smallest acorns die without enough nutrients and the largest acorns are eaten by squirrels, the only acorns left that actually survive long enough to make more oak trees are the medium-sized ones. That’s conflicting selection at work!
In Akiyama and Agren’s paper, the researchers study conflicting selection on the timing of germination, or sprouting, of a small flowering plant in the mustard family called Arabidopsis thaliana.
In order for plants to contribute genetic material to the next generation, they need to survive, and they need to reproduce. In this study, plants that sprouted early experienced lower survival as seedlings, but if they did survive to become adult plants, the adults had better survival and produced more offspring. On the other hand, plants that sprouted later experienced higher survival as seedlings, but out of the survivors, the adults had lower survival and produced fewer offspring than the plants that sprouted early.
In a situation like this where there are complicated pros and cons associated with sprouting early or late, which plants win the fitness game?
To find out, the authors measured overall fitness of the plants that sprouted at different times and found that the advantages of sprouting early outweighed the disadvantages: plants that sprouted earlier had higher overall fitness.
A word of caution from the authors: this study only took place over one year, which is not enough time to generalize these results as a consistently winning strategy for this population of plants. For example, during the year of this study, the fall and winter were fairly cool. This means that the plants that sprouted earlier may have had two advantages related to that year’s weather: 1) even though the early-sprouting seedlings were small and delicate in the fall, they may have survived drought conditions better than they usually would at that size because the fall was cooler than normal, and 2) because the early-sprouting plants had more time to grow big before winter came, they may have had an advantage over the smaller, later-sprouting plants because winter was cold and larger plants have a better chance of surviving the winter.
This is why it’s important to replicate studies – in this case, repeat it with different plants, in different places, over multiple years, etc. – before assuming all plants of the same species or even the same population employ the same early-sprouting strategy all the time. If the fall and winter had been warmer, the researchers may have found completely different results!
Why should you care?
This paper illustrates an important point about the complexity of nature – often, what’s really going on isn’t what seems initially obvious, or even what seems obvious after the second or third or fiftieth time an experiment has been done on it! Science is a slow process, and each paper like this one is a small brick added to a wall of knowledge that will always have gaps in it. Only with much rigorous science can we make the gaps smaller and smaller and the wall sturdier over time.
Akiyama, R. & Agren, J. 2013. Conflicting selection on the timing of germination in a natural population of Arabidopsis thaliana. Journal of Evolutionary Biology 27:193-199.
Gomez, Jose M. 2004. Bigger is not always better: Conflicting selective pressures on seed size in Quercus ilex. Evolution 58(1):71-80.