Showing posts with label pollination. Show all posts
Showing posts with label pollination. Show all posts

Friday, November 30, 2018

Un-BEE-lievable: The Buzz on Native Bee Conservation in Canada

Guest post by University of Toronto-Scarborough MEnvSc Candidate Rachel Siblock

Unless you’ve been living under a rock (much like native mining bees in Canada), you’ve probably seen the numerous campaigns to “Save the Bees”. Bee species across the globe are in decline. There are many factors that contribute to this decline, such as pesticide use, colony collapse, disease, habitat loss, and climate change1. Many of these factors interact with one another, exacerbating the consequences and impacts. Conservation efforts are being implemented to try to stop the loss of these pollinators, and the valuable services they provide to humans. Canada is no exception. There are local, provincial, and national policies and programs operating and currently being developed in order to reduce the impacts of these threats. In the past few years, programs like The Bee Cause, Bees Matter, Feed the Bees, and others have implemented programs and recommendations in order to increase the bee populations in Canada. Honey Nut Cheerios has even campaigned to get the public engaged and involved in the conservation of bees. These programs, however, all have one common issue: they focus their efforts on Honey Bees. 


An example of a campaign by Honey Nut Cheerios, focusing on honey bees. 
There are no native honey bees in Canada. The most well-known bee in Canada was not even present in the country until it was introduced from Europe in the 1600s2. The European Honey Bee was intentionally introduced to Canada for honey production, and since has increased in number dramatically, both in farmed and wild colonies. Honey bees have large colonies, allowing them to be easily managed and farmed. They also pollinate crops and produce honey, which may make them seem more economically valuable than their native, non-honey-producing counterparts. However, there have been unexpected impacts of the introduction of the European Honey Bee on native bee species in Canada.
            There are over 800 native bee species in Canada. While there are many different types of bees in Canada, the best understood group of native bees are bumble bees. Bumble bees have the ability to buzz pollinate, which allows them to obtain pollen from plants with pollen that is difficult to extract. Many of these plants are economically valuable, such as kiwi and blueberry crops. This, along with general pollination, makes managed populations of bumble bees worth several billion dollars annually3. Bumble bees naturally have low genetic diversity and can be subject to inbreeding depression, leading to declining populations and making the some species more vulnerable to extinction4. Threats can then interact with these low population levels, and intensify population loss. 
A male Rusty-patched Bumble Bee, one of Canada’s native bee species. It is currently listed as endangered in Canada.
Aside from facing the same threats as honey bees, native bumble bees are also threatened by the very presence of honey bees. Competition for resources with honey bees is a major threat to native bumble bees. A study performed in the United Kingdom found that bumble bees at sites with high honey bee density were significantly smaller in body size when compared to their relatives at sites with low honey bee density5. An additional study discovered a reduction of native bumble bee colony success when colonies were experimentally exposed to honey bees6. Honey bees generally produce larger colony sizes which can store a larger amount of resources than bumble bees. They also have the ability to communicate with one another about valuable floral resource locations7. Honey bees have a larger foraging range than native bumble bees, and have an increased ability to forage on introduced plant species7. These adaptations allow honey bees to outcompete native bumble bees, and commandeer sparse resources in the area.
            Threats from honey bees do not just end at competition; pathogens and parasites specifically adapted to honey bees have been shown to have the ability to spread to wild bumble bee populations. Managed honey bees are known to carry higher than natural levels of pathogens8, which can be transmitted to wild bumble bee populations when the bees interact. In particular, two pathogens endemic to honey bees, C. bombi and N. bombi, are wreaking havoc on bumble bee populations. While these pathogens do not have lethal effects, their sublethal effects can be devastating to colonies. These pathogens cause reduced pollen loads, a decline in flowers visited per minute, slower growth rates of colonies, decreased queen reproductive rates, shortened life spans and diminished colony growth8. With small populations already, entire bumble bee colonies can be wiped out by these pathogens. Honey bee parasites, such as the Small Hive Beetle, have also been shown to be able to spread to bumble bee colonies, where they consume the wax, pollen, and nectar stores of hives8. While honey bees have co-evolved with these parasites and pathogens for eons, bumble bees have not had the time to adapt to these threats, making them much more vulnerable to these hazards. 
Small Hive Beetle infestation in a honey bee colony. 
But why do we care about losing native bees? The same concerns about the loss of honey bees applies to native bees. Native bee species pollinate crops and flowers, which we depend on for food. It is estimated that about one in three bites of food we consume can be traced back directly to pollination by bees and other pollinators. However, native bees have been found to be more effective pollinators than honey bees. Some plant species in Canada rely solely on native bees for their pollination. With the loss of native bees, these plants will also become endangered, along with many other food crops requiring pollination. Additionally, there is a severe lack of research into native bees. Research tends to focus on honey bee populations, resulting in much more knowledge of honey bee behaviours, adaptations, actions, and responses to stressors. The truth is, we don’t know much about native bee species in Canada. We have no idea what the consequences of the loss of these species will be. However, this does not excuse us from protecting these bees. If anything, this lack of knowledge should increase our urge to protect them, so we have the opportunity to learn about them in the future.
            The native bee species in Canada share little life history traits with the European Honey Bee8, making many conservation efforts that focus on honey bees unsuccessful. Focusing conservation efforts on one species may not address the specific needs of native bees. In addition, by focusing on improving honey bee populations, there will be increased stress on native bees, which will lead to a decline in their populations. If we continue with these conservation strategies, we may threaten native species further.
            An increase in honey bee populations will increase parasite and pathogen levels in native bees, and also increase the competition between honey bees and native bees. So what can you do to focus conservation efforts on native Canadian bees? For starters, avoid the use of pesticides, which will decrease already low populations8. Improve your knowledge of bee species, and report invasive or introduced species in areas used by native bee species. Plant a wide variety of native plants with high pollen and nectar concentrations to ensure newly emerging bees have the resources they need to survive. And finally, avoid tilling, mowing, or burning in areas where native bee species, particularly ground dwelling species, are known to live. With increased knowledge of native bee needs, and species specific conservation efforts, it is hoped that native bee species will begin to rebound. Let’s BEE positive!

BEE Informed – To get involved with native bee conservation check out these links:


BEE-bliography:
    1.     Pettis, J.S., and K.S. Delaplane. 2010. Coordinated responses to honey bee decline in the USA. Adipologie 41:256-263.
    2.     van Engelsdorp, D., and M.D. Meixner. 2010. A historical review of managed honey bee populations in Europe and the United Sates and the factors that may affect them. Journal of Invertebrate Pathology 103:80-95.    
    3.     James, R., and T.L. Pitts-Singer. 2008. Bee Pollination in Agricultural Ecosystems. Oxford University Press, USA.
    4.     Zayed, A., and L. Packer. 2005. Complementary sex determination substantially increases extinction proneness of haplodiploid populations. Proceedings of the National Academy of Sciences of the United States of America 102:10742-10746.
    5.     Goulson, D., and K. Sparrow. 2009. Evidence for competition between honey bees and bumble bees: Effects on bumble bee worker size. Journal of Insect Conservation 13:177-181.
    6.     Thomson, D. 2004. Competitive interactions between the invasive European honey bee and native bumble bees. Ecology 85:458-470.
    7.     Goulson, D. 2003. Effects of introduced bees on native ecosystems. Annual Review of Ecology, Evolution, and Systematics 34:1-26.
    8.     Colla, S.R. 2016. Status, threats and conservation recommendations for wild bumble bees (Bombus spp.) in Ontario, Canada: a review for policymakers and practitioners. Natural Areas Journal 36:412-426.

Image Sources:
  1. https://bringbackthebees.ca
  2. https://inaturalist.com
  3. http://beeaware.org.au/archive-pest/small-hive-beetle/#ad-image-0

Friday, September 12, 2014

Do green roofs enhance urban conservation?

ResearchBlogging.orgGreen roofs are now commonly included in the design of new public and private infrastructure, bolstered by energy savings, environmental recognition and certification, bylaw compliance, and in some cases tax or other direct monetary incentives (e.g., here).  While green roofs clearly provide local environmental benefits, such as reduced albedo (sunlight reflectance), storm water retention, CO2 sequestration, etc., green roof proponents also frequently cite biodiversity and conservation enhancement as a benefit. This last claim has not been broadly tested, but existing data was assessed by Nicholas Williams and colleagues in a recent article published in the Journal of Applied Ecology.

Williams and colleagues compiled all available literature on biodiversity and conservation value of green roofs and they explicitly tested six hypotheses: 1) Green roofs support higher diversity and abundance compared to traditional roofs; 2) Green roofs support comparable diversity and composition to ground habitat; 3) Green roofs using native species support greater diversity than traditional green roofs; 4) Green roofs aid in rare species conservation; 5) Green roofs replicate natural communities; and 6) Green roofs facilitate organism movement through urban areas.

Photo by: Marc Cadotte


What is surprising is that given the abundance of papers on green roofs in ecology and environmental journals, very few quantitatively assessed some of these hypotheses. What is clear is that green roofs support greater diversity and abundance compared to non-green roofs, but we know very little about how green roofs compare to other remnant urban habitats in terms of species diversity, ecological processes, or rare species. Further, while some regions are starting to require that green roofs try to maximize native biodiversity, there are relatively few comparisons, but those that exist reveal substantial benefits for biodiverse green roofs.

How well green roofs replicate ground or natural communities is an important question, with insufficient evidence. It is important because, according to the authors, there is some movement to use green roofs to offset lost habitat elsewhere. This could represent an important policy shift, and one that may ultimately lead to lost habitats being replaced with lower quality ones. This is a policy direction that simply requires more science.

There is some evidence that green roofs, if designed correctly, could aid in rare species conservation. However, green roofs, which by definition are small patches in an inhospitable environment, may assist rare species management in only a few cases. The authors caution that enthusiasm for using green roofs to assist with rare species management needs to be tempered by designs that are biologically and ecologically meaningful to target species. They cite an example where green roofs in San Francisco were designed with a plant that is an important food source for an endangered butterfly, Bay Checkerspot, which currently persists in a few fragmented populations. The problem was that the maximum dispersal distance of the butterfly is about 5 km, and there are no populations within 15 km of the city. These green roofs have the potential to aid in rare species conservation, but it needs to be coupled with additional management activities, such as physically introducing the butterfly to the green roofs.

Overall, green do provide important environmental and ecological benefits in urban settings. Currently, very few studies document the ways in which green roofs provide ecological processes and services, enhance biodiversity, replicate other ground level habitats, or aid in biodiversity conservation. As the prevalence of green roofs increases, we will need scientifically valid ecological understanding of green roof benefits to better engage with municipal managers and affect policy.

Williams, N., Lundholm, J., & MacIvor, J. (2014). Do green roofs help urban biodiversity conservation? Journal of Applied Ecology DOI: 10.1111/1365-2664.12333

Tuesday, April 29, 2014

Unexpected effects of global warming in novel environments: butterflies emerge later in warming urban areas.

ResearchBlogging.orgThere is now ample evidence that warming temperatures cause advances in the timing of organismal activity (i.e., phenology). Studies have shown that rising temperatures are responsible for earlier plant leafing and flowering (Miller-Rushing & Primack 2008, Wolkovich et al. 2012), pest insect emergence and abundance (Willis et al. 2008), and even local species loss and reduced diversity (Willis et al. 2008). One emerging expectation from global warming studies is that insects should emerge earlier since winters are milder and spring temperatures are warmer. This expectation should hold so long as high temperatures or other environmental stressors don’t adversely affect the insects. And the concern about shifts in emergence and insect activity is the potential for mismatches between plant flowering and the availability of pollinators (Willmer 2012) –if insects emerge too soon, they may miss the flowers.

Photo by Marc Cadotte


In a forthcoming paper in Ecology by Sarah Diamond and colleagues study 20 common butterfly species across more than 80 sites in Ohio. These sites were located in a range of places across a rural to urban gradient. Instead of finding earlier emergence in warmer places, which were typically urban areas, they found that a number of species were delayed in warmer urban areas. Even though the butterflies might emerge earlier in warmer rural habitats, they were adversely affected in urbanized areas. 

These results highlight the need to consider multiple sources of stress from different types of environmental change. Observations from a few locales or from controlled experiments may not lead to conclusions about interactive influences or warming and urbanization, and that's why this study is so important. It observes a counter-intuitive result because of the influence of multiple stressors. 

A next step should be to determine if pollinator-plant interactions are being disrupted in these urban areas. The reason why we should care so much about pollinator emergence is that they provide a key ecological service by pollinator wild, garden, and agricultural plants, as well has being an important food source to other species. A mismatch in timing and disrupt these important interactions.

References

Diamond S.E., Cayton H., Wepprich T., Jenkins C.N., Dunn R.R., Haddad N.M. & Ries L. (2014). Unexpected phenological responses of butterflies to the interaction of urbanization and geographic temperature. Ecology.

Miller-Rushing A.J. & Primack R.B. (2008). Global warming and flowering times in Thoreau's Concord: a community perspective Ecology, 89, 332-341.

Roos J., Hopkins R., Kvarnheden A. & Dixelius C. (2011). The impact of global warming on plant diseases and insect vectors in Sweden. Eur J Plant Pathol, 129, 9-19.

Willis C.G., Ruhfel B., Primack R.B., Miller-Rushing A.J. & Davis C.C. (2008). Phylogenetic patterns of species loss in Thoreau's woods are driven by climate change. Proceedings of the National Academy of Sciences, 105, 17029-17033.

Willmer P. (2012). Ecology: pollinator-plant synchrony tested by climate change. Curr. Biol., 22, R131-R132.

Wolkovich E.M., Cook B.I., Allen J.M., Crimmins T.M., Betancourt J.L., Travers S.E., Pau S., Regetz J., Davies T.J., Kraft N.J.B., Ault T.R., Bolmgren K., Mazer S.J., McCabe G.J., McGill B.J., Parmesan C., Salamin N., Schwartz M.D. & Cleland E.E. (2012). Warming experiments underpredict plant phenological responses to climate change. Nature, 485, 494-497.


Diamond, S., Cayton, H., Wepprich, T., Jenkins, C., Dunn, R., Haddad, N., & Ries, L. (2014). Unexpected phenological responses of butterflies to the interaction of urbanization and geographic temperature Ecology DOI: 10.1890/13-1848.1

Monday, February 11, 2013

The birds and the bees and the microbes

Vannette et al. 2013. “Nectar bacteria, but not yeast, weaken a plant-pollinator mutualism”. Proceedings of the Royal Society B-Biological Sciences.

"When we try to pick out anything by itself, we find it hitched to everything else in the Universe."- John Muir

You can’t help but marvel at the complexity of ecology, at the intricacy and multiplicity of species interactions. But this complexity is also problematic. For many ecologists, it becomes necessary to focus on a single type of interaction, or on interactions limited to only a few species. But real ecological systems are hardly ever limited to a single important process. They might include competition, mutualism, facilitation, predation, environmental constraints and fluctuations, additive and interactive effects, nonlinearities, thresholds and emergent properties. Can knowledge of  omplexity emerge from simplicity? Can simplicity emerge from complexity? These are important and longstanding questions in ecology, the focus of some of our smartest minds. We may not have the answer yet, but if nothing else, it is helpful when experimental work in community ecology attempts to explore multiple interactions.

For example, some of the work from Tadashi Fukami’s lab is focused on how communities of microorganisms (yeast and bacteria species) assemble in Mimulus aurantiacus nectar. In the past, this work has focused particularly on priority effects and resource competition, which plays an important role in structuring these communities. While past work has suggested the importance of pollinators as a dispersal vector for microorganisms, fascinating new work suggests that microbial communities have important effects on pollinators and their mutualistic interactions with the host plant as well.

Vannette et al. (2013) focused on the effects of the two most abundant species in Mimulus nectar, Gluconobacter sp., an acid-producing bacteria, and Metschnikowia reukaufii, a yeast. They then looked at three related questions – how do nectar microbes affect nectar chemistry, how do they affect nectar removal by hummingbird pollinators, and how to they affect pollination success and seed set. Basically, do nectar microbes disrupt important mutualistic interactions between the plant and their pollinators, or are their effects neutral?

This is where the story becomes interesting. Both types of microbes altered nectar chemistry, but in different ways. The bacteria acidified the nectar (to ~ pH 2.0) far more than the yeast species, and tended to also reduce the sugar content of the nectar far more than the yeast. Hypothesizing that these changes could ultimately affect pollinator preference, the authors then filled artificial flowers with nectar containing either the bacteria, yeast, or no microbes. Half of these flowers were bagged to prevent hummingbird access. Compared to the bagged controls, flowers with bacteria-inoculated nectar had less nectar removed than either yeast-inoculated or sterile nectar. It appeared that nectar removal was related to the changes in chemistry driven by bacterial growth in the nectar. Finally,  the authors looked pollination success in relation to microbial inoculation. Flowers inoculated with bacteria did indeed have less pollination success (measured as the number of stigmas closed) and had decreased seed numbers. Microbial communities were not isolated from the ecology of the plant.

Perhaps none of this is that surprising – hummingbirds are intelligent and will preferentially feed, and pollinator choice is important for plant fitness. However, these bacteria and yeast species are specialized for growth in the hypertonic nectar environment and their continued presence in the ecosystem depends on dispersal from one flower to the next before their host flower dies. The transient nature of this nectar habitat suggests that obtaining a dispersal vector should be important. The fact that Gluconobacter alters nectar chemistry in a way which negatively affects their likelihood of movement to other patches suggests an interesting paradox and a complicated relationship between plants, their nectar microbes, and pollinators. Gluconobacter species growing in Mimulus flowers produce acidifying H+ ions and reduce sugar concentrations in nectar – this increases their likelihood of winning competitive interactions with other microbes in the nectar, which should select for the maintenance of acidifying, sugar-reducing characteristics. But on the other hand, these characteristics reduce the likelihood of being transported to new flowers and persisting in the metacommunity. Further, these pollinator-decreasing characteristics may result in selection by the Mimulus plants for nectar compounds that reduce microbial contamination. So understanding competitive interactions in microbial communities, or understanding pollinator-plant interactions, or understanding pollinator-microbial interactions on their own might be inadequate to understand the important ecological and evolutionary processes structuring the entire system.

Given that the question of simplicity vs. complexity is still so difficult and at least for me, uncertain, I would hesitate to draw a general conclusion about whether this is the kind of work all community ecologists should strive for. But it seems that recognizing ecological and evolutionary context is key, whether you work with Arabidopsis, microcosms, or tropical forests.



Tuesday, January 11, 2011

Who is a scientist, I am a scientist: the bees of Blackawton

ResearchBlogging.orgIn discussions of the larger societal implications of scientific findings, the question of who is a scientist is frequently asked. I've talked with with creationists who invoke the authority of someone who has a PhD in a scientific discipline and happens to share their belief of supernatural origins, as a scientific authority. Does the fact that I have a PhD in ecology and evolutionary biology make me scientist or is being scientist something more?

This is an important question. It goes to the core of whose authority we believe for public discussion of such issues as climate change, evolution, risks of vaccines, and so on. Regardless of how we define 'scientist', a scientist participates in science by publishing peer-reviewed research articles in scientific publications. This notion of who is a scientist has been enjoyably stretched by the publication of a paper in Biology Letters by a group of elementary school children from Blackawton, UK. In consultation with a academic scientist and under the supervision of teachers, 25 8-10 year olds devised and carried out an experiment on bee visual perception and behavior, and wrote up their results into a publishable manuscript.

The students trained bees by offering them nectar rewards in different color containers. They then allowed these trained bees to forage in multicolored arenas and they conclusively show that the bees unambiguously select the colored containers they were trained on. Bess learn and adapt their behavior based on previous experience.

Publishing a paper by a group of children may sound like a gimmick, but the study is very interesting. The commentary from the journal says it best: "The children's findings show that bees are able to alter their foraging behaviour based on previously learned colours and pattern cues in a complex scene consisting of a (local) pattern within a larger (global) pattern . As there has been little testing of bees learning colour patterns at small and large scales, the results can add considerably to our understanding of insect behaviour."

The paper is extremely enjoyable to read and will have you chuckling to yourself. Sincerity pours from the words and I was left wondering if I could have reasoned so well at that age. The children develop hypotheses using information available to them, such as watching Dave Letterman's 'Stupid Dog Tricks'. Reading this article made me realize why I love being scientist. The students note that "This experiment is important, because, as far as we know, no one in history (including adults) has done this experiment before" and because they were given the opportunity to carryout this study they "also discovered that science is cool and fun because you get to do stuff that no one has ever done before". Too true. I could not have said it better myself.

Being scientist can mean a lot of things, it can mean knowledge (which the Latin origin, Scientia means), it can mean training and acquired skills, but at its core, being a scientist means conducting research, testing hypotheses and writing publications that are deemed acceptable by other scientists. Therefore the children of Blackawton are scientists, I am a scientist.

Blackawton, P., Airzee, S., Allen, A., Baker, S., Berrow, A., Blair, C., Churchill, M., Coles, J., Cumming, R., Fraquelli, L., Hackford, C., Hinton Mellor, A., Hutchcroft, M., Ireland, B., Jewsbury, D., Littlejohns, A., Littlejohns, G., Lotto, M., McKeown, J., O'Toole, A., Richards, H., Robbins-Davey, L., Roblyn, S., Rodwell-Lynn, H., Schenck, D., Springer, J., Wishy, A., Rodwell-Lynn, T., Strudwick, D., & Lotto, R. (2010). Blackawton bees Biology Letters DOI: 10.1098/rsbl.2010.1056


Thursday, January 14, 2010

Plant genotypic diversity supports pollinator diversity

ResearchBlogging.orgResearch over the past 20 years has shown that plant communities with greater diversity maintain higher productivity, greater stability and support more diverse arthropod assemblages. More recently, several experiments have shown that interspecific diversity (namely genotypic differences) also affects community functioning. Pollination is often considered an essential function, and does plant genotypic diversity affect pollinator diversity and frequency?

In a recent paper in PLoS ONE, Genung and colleagues test whether plant genotypic diversity affects pollinator visits. They use an experimental system set-up by Greg Crutsinger that combines multiple genotypes of the goldenrod, Solidago altissima, and record pollinator visits over two years. Experimental plots contained 1, 3, 6, or 12 genotypes of S. altissima. After accounting for differences in abundance, Genung et al. show that as genotypic diversity increases, both pollinator richness and number of visits to the plot significantly increase. This increase is greater than expectations of randomly simulated assemblages combining proportional pollinator visits from monocultures.

The previous research at the species-level has made a persuasive rationale to protect species diversity in order to maintain ecosystem functioning. Now, research like this is making a case that there are consequences for not explicitly considering genetic diversity in conservation planning and habitat restoration.

Genung, M., Lessard, J., Brown, C., Bunn, W., Cregger, M., Reynolds, W., Felker-Quinn, E., Stevenson, M., Hartley, A., Crutsinger, G., Schweitzer, J., & Bailey, J. (2010). Non-Additive Effects of Genotypic Diversity Increase Floral Abundance and Abundance of Floral Visitors PLoS ONE, 5 (1) DOI: 10.1371/journal.pone.0008711

Wednesday, October 7, 2009

Exotic plants integrate into plant-pollinator networks

ResearchBlogging.orgAt almost any spot on the globe, there are species present that are not native to that locale, having been transported by human activities. Whether and how exotic species impact communities is a multifaceted problem that requires understanding the multitude of direct and indirect species interactions that occur. In a paper published in the Proceedings of the Royal Society, B, Montserrat Vila and colleagues asked if exotic plants where integrated into plant-pollinator networks, and whether this integration had any observable impacts on these networks. This is an important question, as most ecological theory predicts that plant-pollinator networks are actually quite resilient to perturbations since most associations tend to be between generalists as opposed to the more susceptible specialists.

They studied invaded plant communities across Europe, observing pollinator visits to flowers in multiple 50 x 50 m plots. They calculated connectance as the number of interactions standardized by network size. They showed that exotics fully integrated into plant-pollinator networks. Exotic species accounted for 42% of all pollinator visits and 24% of all network connections -a testament to the overall abundance of exotics in many communities. However, these exotics did not affect overall changes in network connectedness, revealing that these networks are quite robust to invasions.

That said, researchers must now ask if this is true in networks that do contain high numbers of specialists (e.g., orchids) or if the relative few specialists in generalist-dominated systems are more susceptible to changes from exotics.

Vila, M., Bartomeus, I., Dietzsch, A., Petanidou, T., Steffan-Dewenter, I., Stout, J., & Tscheulin, T. (2009). Invasive plant integration into native plant-pollinator networks across Europe Proceedings of the Royal Society B: Biological Sciences, 276 (1674), 3887-3893 DOI: 10.1098/rspb.2009.1076