Plants, Pollinators, and Imposters Katie V. Spellman University of Alaska Fairbanks Institute of Arctic Biology

Grade Level: 7-12 Alaska State Science Standards: Subject: Science Target Skills: inference, interpretation, communication Duration: 45 min- 1 hr Setting: Classroom Vocabulary: competition, explanatory variables, response variables, controlled variables, extraneous variables INSTRUCTIONAL GOALS  Students will understand the diversity of possible interactions between invasive plants, pollinators and native plants, and the need to investigate these interactions in Alaska. PERFORMANCE OBJECTIVE  Students will complete a jigsaw of current research on invasive plants, pollinators and native plant species and report the research findings to the class.  Students will create a flow map of the possible effects invasive plants could have on pollination, and the effects this could have on native plants and people.  Students will design a hypothetical experiment that they could conduct to determine the relationship between an invasive plant, pollinators and a native plant in Alaska. MATERIALS  Research briefs at the end of this lesson.  Large chart paper and markers TEACHER BACKGROUND ADVANCED PREPARATION  

Make copies of research briefs, enough for students in five groups to read the briefs. Preview “Pollinator Attraction” video online

PROCEDURE 1. (Gear up) Watch “Pollinator Attraction” you-tube video at http://www.youtube.com/watch?v=6xt-A08H8wM. Discuss the problem of declining pollinators and increasing invasions, and how that might impact native plants. Pollinators are decreasing all over the world, and invasive plants are

spreading at a faster and faster rate throughout Alaska. We have no idea how invasive plants could impact pollinators and the native plants of Alaska. The University of Alaska research team in this video has a lot of work to do. We can look to research done in other parts of the world. 2. (Explore) Jigsaw of research briefs. Divide the class into 5 groups. Each group will read the research summary and discuss the findings of that particular study. Groups will report what they learned to the whole class. 3. (Generalize) Make a flow map of the general types of interactions that researchers have found between invasive plants, pollinators, and native plants in other parts of the world (see Hyerle and Yeager 2007 for detailed background on flow maps). Non-native plant invasion should be the event in the center bubble, with the next level of bubbles being the potential impacts invasive plants could have on pollinators. The third level of bubbles should be the subsequent impact that changes in pollinators could have on native plants or crops. Add any impacts that these outcomes could have on humans. See example concept map below. No effect on other plants

Reduced fruit/seed set

No change in fruit/seed set

Pollinator carries contaminated pollen

Non-Native Plant Invasion

Less food crops pollinated

Reduced fruit/seed set

Decrease in pollinator visits to native plants

No effect on pollinators

Increase pollinator abundance Increase in pollinator visit rates to all plants

Increased fruit/seed set

More food crops pollinated Increased fruit/seed set

4. (Apply) Based on the information presented, have students return to their small group and brainstorm a simple experiment that they could do to test the relationship between invasive plants, pollinators and native plants in Alaska. Write a testable hypothesis. What would be your response variable? What would the explanatory variable be? Are there any variables you must control for?

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Explanatory variables answer the question "What do I change?" Response variables answer the question "What do I observe?" Controlled variables answer the question "What do I keep the same?" Extraneous variables answer the question "What less interesting variables might mediate the effect of the explanatory variable on the response variable?"

EVALUATION Students share their proposed experiments orally to the class. REFERENCES Bartomeus, I., M. Vila and I. Steffan-Dewenter. 2010. Combined effects of Impatiens glandulifera invasion and landscape structure on native plant pollination. Journal of Ecology 98:440–450. Brown, B.J., and R.J. Mitchell. 2001. Competition for pollination: effects of pollen of an invasive plant on seed set of a native congener. Oeeologia 129:43-49. Brown, B.J., R.J. Mitchell, and S.A. Graham. 2002. Competition for pollination between an invasive species (purple loosestrife) and a native cogener. Ecology 83. 2328–2336. Chittka, L., and S. Schürkens. 2001. Successful invasion of a floral market: An exotic Asian plant has moved in on Europe’s riverbanks by bribing pollinators. Nature 411:653. Hyerle, D. and Yeager, C. 2007. Thinking maps: a language for learning. Cary, NC: Thinking Maps, Inc. Moragues, E. and A. Traveset. 2005. Effect of Carpobrotus spp. on the pollination success of native plant species of the Balearic Islands. Biological Conservation 122: 611–619. Spellman, K.V. 2011. Pollinator Attraction: do exotics do it better? YouTube research outreach video. http://www.youtube.com/watch?v=6xt-A08H8wM. Tepedino, V.J., B.A. Bradley, T.L. Griswold. 2008. Might flowers of invasive plants increase native bees carrying capacity? Intimations from Capitol Reef National Park, Utah. Natural Areas Journal 28: 44–50.

Invasion and Pollination Research Briefs Combined effects of Impatiens glandulifera invasion and landscape structure on native plant pollination Ignasi Bartomeus, Montserrat Vila and Ingolf Steffan-Dewenter Journal of Ecology (2010) 98, 440–450

This research team thought that both invasive plants and changes in the landscape such as habitat fragmentation due to human development could impact the pollination of native plants. To test if these factors influenced pollination, the research team studied 14 sites near streams in central Germany. The sites spanned a gradient of land development, from intact natural landscape to heavily used agricultural landscapes. At each site they added several pots of the native plant Raphanus sativus to plots with and without the invasive plant ornamental jewelweed (Impatiens glandulifera, pictured left). Ornamental jewelweed is highly attractive to pollinators and produces a lot of flowers and nectar. The researchers surveyed the pollinators that came to each plot, and then counted the number of seeds that the potted native plants produced after being left out to be pollinated in the invaded and uninvaded plots. They found that in the plots with the invasive ornamental jewelweed, the invasive plant was visited at higher rates than the native plants. However, when they compared the overall visitation rates of plant in the invaded and univaded plots, there was no difference in pollinator visitation rates. The researchers conclude that this invasive plant did not outcompete the native plants for pollinators. As for the landscape structure question, the research team found that bumblebee densities were higher in the more intensively cultivated landscapes than other landscapes, and in areas with the ornamental jewelweed. They interpreted this result to indicated that the dynamics of native pollinators is driven by plants with rewarding flowers dominating the landscape, be it lots of flowering crops or lots of flowering invasive plants. For other types of pollinators like hoverflies and other types of bees, the densities did not vary with the type of landscape or the presence of the invasive plants.

Competition for pollination: effects of pollen of an invasive plant on seed set of a native congener Beverly J. Brown and Randall J. Mitchell Oeeologia (2001) 129:43-49

This research team from Kent State University in Ohio did a combination of hand pollination trials and a pollen dye experiment to determine if the invasive plant purple loosestrife (Lythrum salicaria, pictured left) could impact the reproductive success of a closely related native plant Lythrum alatum. These two species flower at the same time and can occur in the same habitats. The research team wanted to know if pollinators transfer pollen between the native and invasive plants. If the invasive plant pollen was being transferred, then the researchers wanted to know if the contaminated pollen, or reduced pollen quality, would have any impact on the reproductive success of the native plant. To see if the pollen was transferred from the purple loosestrife to it’s closely related native plant (cogener), the researchers put fluorescent orange dye articles on the anthers of the invasive purple loosestrife. They then examined stigmas of the native L alatum each day to see how many dye particles were carried. They found that about two in every three native flowers had received dye from the invasive plant, indicating that the pollen was being transferred between the native and non-native plants. To determine if the pollen from the invasive plant effected the seed production of the invasive plant, the researchers hand pollinated the native plants with invasive pollen using a toothpick. They compared the amount of seeds produced in native plants receiving only invasive plant pollen with plants where they pollinated mixed invasive and native pollen, and control plants where they used only native pollen. They found that if the native flower received native pollen, it had high seed set, and when it received the mixed native and invasive pollen, seed set was reduced by nearly 30%. If the native flower received only invasive pollen, the plant had extremely low seed set. The study concludes that competition for pollination by flowering invasive species may pose a threat to native species by clogging the stigma or style and reduce seed set. The researchers then followed up their experiments with a two-year study1, where they compared the pollinator visitation rates in areas where they planted only purple loosestrife, areas where they planted only the native cogener, and areas where they planted mixtures of the invasive and native. In this study they found that the invasive plant reduced the pollinator visitation rate to the native plants. Again, they found that seed set was reduced when the native and invasive were growing together. 1

Brown, B.J., R.J. Mitchell, and S.A. Graham. 2002. Competition for pollination between an invasive species (purple loosestrife) and a native cogener. Ecology 83. 2328–2336.

Succcessful invasion of a floral mark ket: An ex otic Asiann plant has moved in on Europe’s E riv verbanks by b bribing pollinators p s. L. Ch hittka and S. Schürkens S Nature (2001) 411:653.

In justt over a century y, ornamental jewelweed j (Imp mpatiens gladullifera) has , inttroduced from the t Himalayas, has taken oveer half th he riverbanks in n Czech Repub blic, and has sp pread rapidly inn Europe and North Am merica. This plant can grow up u to 2 meters tall an nd produces abo out 2,500 seeds per plant. Yo ou can imaginee it is a good competitor for space an nd resources in n areas it invadees. This Germaan research team m suspected th hat the nectarrich, showy flowers were also conttributing to its success by nators and reducing the amoun nt of seeds compeeting for pollin producced by native plants. p The reseearchers began n by quantifyinng the am mount of nectarr rewards that the t invasive plaant produced compaared to native plants p on riverb banks in Germaany. They found that ornamentaal jewelweed produced p more sugar per houur for theeir nectar than ever recorded for any native plant in centraal Europe. They then seet up a compettition experimeent between thee invasiv ve and a highly y rewarding naative plant, Stacchys palustris. They recorded r the nu umber of visitss pollinators made to the puree patchees of the nativee flowers in 10 minute intervaals. A few dayss later, they t then hauleed large ornam mental jewelweeed plants in bucketts into the nativ ve plant patchees. After a few days of lettingg the plaants sit, they went w back and re-observed r thee number of pollinaator visits. Theey found that th he introduction n of the invasivve plant reduced r pollinaator visits to th he native plantss by 50%. The researchers suspected that reduced pollinator visitation could lead to o less sed produ uction, and red duced populatio on sizes of the native plant. To test this, they coun nted seeds prod duced by the native plant in pure patches, p and in n stands where ornamental jewelw weed grew mix xed in with the native plant. The T seed set off the native plants wass on average 25 5% less in patcches with the invasiv ve than in puree patches. The researchers con ncluded that compeetition for polliinators from th his invasive plaant had a strongg negative impact on th he fitness of a native plant.

Effect of Carpobrotus spp. on the pollination success of native plant species of the Balearic Islands Eva Moragues and Anna Traveset Biological Conservation (2005) 122:611–619

A research team in Spain looked at the impact nonnative plant invasions had on pollination of native plant species in the Balearic Islands off the south east coast of Spain. They chose the invasive plant known as hottentot fig (Carpobrotus spp., pictured above), which is quite showy and competes with native species on the islands, many of which are protected species. They investigated four native species that share both habitat and flowering times with the hottentot fig (Cistus monspeliensis, Cistus salviifolius, Anthyllis cytisoides and Lotus cytisoides). They hypothesized that the showy fig flowers would compete with the other flowers for pollinator visitation. To test their hypothesis, they observed and counted pollinator visits to flowers in areas both invaded by the hottentot fig and adjacent areas that remained uninvaded. They also looked at stigmas of the different native species under the microscope and counted

the number of exotic pollen grains present. They then looked at the reproductive success of the different native species in both invaded and uninvaded sites by counting the number of seeds produced. They found that the interaction between the native plants, pollinators and the invasive fig plants was different depending on the native species. Their data showed that hottentot fig competed for pollinators with only one of the four native species (L. cytisoides), The invasive plants had a facilitative effect in two other species (C. salviifolius and A. cytisoides), increasing the amount of pollinator visits the native flowers received in the invaded areas compared to the uninvaded areas. The invasive had no effect on the fourth native species (C. monspeliensis). The researchers concluded that the invasive hottentot fig can have positive, negative or neutral impacts on pollination of native plants depending on the species.

Might flowers of invasive plants increase native bees carrying capacity? Intimations from Capitol Reef National Park, Utah V.J. Tepedino, B.A. Bradley, T.L. Griswold Natural Areas Journal (2008) 28: 44–50.

National parks in the United States are becoming increasingly pressured by invasive plant species, which can impact both native plants and pollinators. Many studies suggest that invasive plants reduce pollinator visits to native plants, resulting in fewer seeds, which could lead to lower numbers of native seedlings. This research team wondered if some invasive plants with abundant rewards for pollinators such as tamarisk (Tarmarix spp., pictured top right) and sweetclover (Melilotus officinalis, pictured bottom right), could actually benefit pollinators such as wild bees. The researchers quantified pollinator visitation to these invasive plant species and compared them to the pollinator visits to seven native plant species in Capitol Reef National Park, Utah. They found that the rewarding invasive plants were visited by twice as many species of wild bees compared to the native plants. Most of the bee species visiting the invasive plants were generalist bees, meaning they don’t specialize in foraging on a particular type of flower. The researchers observed bees collecting pollen and nectar from the invasive plants, suggesting that the invasives were providing resources for bees to rear their young. They conclude that, while invasive plants may compete with native plants for pollinators when they are first introduced, as the invasive becomes naturalized, they are likely to provide more resources to generalist bees and increase the overall carrying capacity and population size of these pollinators.