I’m back with more updates from our team trip to Terre Haute for MEEC 2019. Today, I want to show off the incredible pollen limitation study poster presented by Tris Dodge. Tris joined Team echinacea this last November when he was a Carleton Extern at the Chicago Botanic Garden for three weeks before winter break. As an intern, Tris did a lot of work gathering and analyzing data on our pollen limitation study. If you want to learn more about that study, check out our background page. If you want to see the work that Tris did specifically, check out the flog posts that he has written. Tris’s flog posts include a direct link to his poster
In his analysis, Tris found out that creating seeds is basically free for echinacea plants. If they produce a lot of seeds one year, they can produce a lot of seeds the next year as well. This was not what we had predicted! Tris used the data from 7 years of the pollen limitation study to show that plants that had zero reproduction did not turn into big-leafed, multi-head super plants, but instead look exactly the same as those heads that produced many achenes.
Tris presenting his poster to Nate
Title: Little cost of reproduction in the long lived perennial, Echinacea angustifolia
Presented at: MEEC 2019 at Indiana State University in Terre Haute, IN
My name is Tris Dodge and I am a winter research extern for the Echinacea Project. I am a senior biology major at Carleton College, interested in understanding how human-driven environmental change is affecting species interactions and causing rapid evolution. I spent the summer of 2017 in Carleton’s restored tallgrass prairies, researching how herbivore exclusion affects soil nutrients and community composition. Last summer, I was a research assistant for two projects at the Rocky Mountain Biological Laboratory (RMBL). I helped gather data on how changing phenology alters the competitive landscape and fitness of perennial wildflowers, and I monitored functional traits, fitness, and glucosinolate chemistry of Boechera stricta in a common garden, as part of a larger genome-wide association study. After graduating from Carleton, I hope to pursue a PhD in ecology or evolution. I enjoy spending my time outdoors and am a member of the cross country and track teams. In my free time, I hike, fly-fish, and knit.
This winter, I am a research extern assisting with projects testing pollen limitation in Echinacea angustifolia and how isolation in space and time affect fitness of Liatris aspera and Solidago speciosa. In practice, each day involves hours of cleaning and counting seeds while thinking about biology. So far, seed counting has allowed me to closely observe the beauty of flower physiology, and has also made me crave sunflower seeds (another Asteraceae). I am very excited to contribute to team Echinacea for these next few weeks!
Wow! These last three weeks passed by super quickly! While the first two weeks were focused on seed cleaning, seed counting, and x-raying, we spent this past week on our independent projects. But that’s not to say this week was easy! In the past 5 days, I wrote exactly 900 lines of code in R to generate the figures and perform the analyses.
To get at how current pollen limitation affects Echinacea growth and future fitness, I performed analyses testing differences in plant traits between pollen exclusion, pollen addition, and open pollination treatments. I did not find evidence that pollination treatment affected either growth or fitness, which indicates that current pollen limitation will not benefit Echinacea in the future. This could be because Echinacea is not resource limited or because the cost of seed production is negligible.
Many thanks to the members of Team Echinacea who helped guide me through this process and made working in the lab such a pleasure!
Reproduction in plants can be limited by access to pollen and resources. We previously found that Echinacea plants in the remnants are pollen limited, meaning that if they had access to more pollen, they would produce more seeds. However, the long-term effects of pollen limitation are unknown. Do plants that are super pollen saturated and have high amounts of pollen have a higher lifetime fitness than plants that are pollen limited? Also, we know that the plants in the remnants are pollen limited, but are the plants in the common garden environment also pollen limited? To answer these questions and more, 13 years ago Gretel randomly selected 39 plants from p1; half of these plants were randomly assigned to the pollen addition group, and the others were assigned to pollen exclusion. Every year, plants in the pollen exclusion have their heads bagged and they are not pollinated, while we hand cross every style in the pollen addition group. An additional 53 plants in p1 were selected to be part of a control group where pollen was neither added nor excluded.
In the summer of 2024, NONE of the original 39 addition/exclusion plants were flowering. If any had been flowering, the exclusion treatment plants would be covered with exclusion bags to prevent pollination, and the addition plants would be hand-pollinated multiple times throughout the summer. One plant in the control group produced a single flowering head.
Collaborator and NDSU postdoc Grace Hirzel places pollinator exclusions bags on Echinacea heads in the remnants. If any of the plants in the polLim experiment from the non-control group had flowered this year, it would’ve looked like this!
You can find more information about the pollen addition and exclusion experiment and links to previous flog posts regarding this experiment at the background page for the experiment.
Supplemental pollen — pollen that an Echinacea head might not otherwise receive—could increase a plant’s fitness. But does this extra pollination lead to a tradeoff in survival or flowering consistency? Since 2012, we have been manipulating the amount of pollen Echinacea plants receive – either no pollen, or lots of pollen – and recording how this affects their fitness and survival. In 2012 and 2013 we identified flowering E. angustifolia plants in experimental plot 1 and randomly assigned one of two treatments to each: pollen addition or pollen exclusion. The team bagged the heads of all plants and hand-pollinated the addition treatment, and did not manipulate the exclusion plants further. Plants receive the same treatment across years.
In summer 2018, 14 of the 26 plants alive in the pollen addition and exclusion experiment flowered, producing a total of 25 heads. This year none of those plants flowered. Of the original 38 plants in this experiment, 12 of the exclusion plants and 14 of the pollen addition plants are still alive. No plants died between 2018 and 2019. This year’s data were unique among the eight years of data collected, because not a single plant in the experiment produced even a single head. The dramatic decrease in flowering rates this year may help or hinder us in analyzing this data set and providing answers to this eight-year question.
Tris did not find significant demographic differences between plants which received pollen exclusion, addition or open pollination treatments.
Start year: 2012
Location: exPt1
Physical specimens: We harvested no specimens this year
Data collected: Plants survival and measurements were recorded as part of our annual surveys in P1 and can be found with the rest of the P1 data in the R package EchinaceaLab.
Michael presented a poster on the polLim experiment at MEEC
2019, which you can find here
Tris also presented a poster on polLim at MEEC 2019, which you can find here
You can find more information about the pollen addition and
exclusion experiment and links to previous flog posts regarding this
experiment at the background page for the experiment.
