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Hey Flog readers, Sam here.
After a quarter of hard work, all of the achenes from my thirty-two flowerheads have been counted, x-rayed, and classified! I am looking forward to analyzing the data next quarter in R through a class Stuart teaches at Northwestern. It’s been quite a journey learning about both the nitty-gritty of going from flower head to data sheet and the conservation biology through which we contextualize our data. Special thanks to Stuart for giving me the opportunity to intern for the Echinacea project, to Amy and Scott for being wonderful, helpful mentors, and to everyone else in the lab for your amazing company and support. If anyone reading this would like to know more about what it is like to intern for the Echinacea Project, feel free to e-mail me at Samuelhamilton2017@u.northwestern.edu.
Best,
Sam
Dear Flog,
Last time I mentioned in passing that Stuart, Amy, Scott, and I had been discussing papers about fire and its potential impact on the reproductive fitness on Echinacea plants. This week I will go into greater detail about what I’ve learned about fire and what our data can teach us about how it impacts prairie health.
Some of our studies taken from previous years have shown us that, even when there are enough bees to carry pollen from plant to plant, Echinacea plants can have difficulties receiving pollen from potential mates. There are a few reasons for this. In our fragmented prairie remnants, Echinacea plants are often far enough apart that pollen collected by a bee will often fall off before it can reach another Echinacea flower. Echinacea plants may also flower in different years, or at different times in the season. This can prevent mating even between close flowers. This mate availability problem is compounded by the fact that Echinacea is self-incompatible, meaning a plant cannot pollinate itself or its close relatives. This means that if a plant flowers and fails to find mates, all the energy it expends to flower and fruit results in no offspring. This is an extraordinary energy cost for no payoff.
Data we have collected seems to suggest that fires may help perennial prairie plants like Echinacea find other mates. Explosive flowering after a large burn is typical for prairie plants. There is some evidence that increased availability of nutrients from burned organic matter and the increased availability of sunlight provide resources for a plant to invest in a costly reproductive structure like a flower. This is probably no different for Echinacea. However, as an added bonus, some of our data seems to show that this explosive flowering may reduce the reproductive isolation of Echinacea plants by increasing the number of synchronous flowering plants. Thus, fire helps Echinacea successfully seed by increasing the number of available mates. Really cool!
The tendency of Echinacea to flower synchronously after a fire could be the result of natural selection, or simply a byproduct of the excellent growing conditions created by fire. In either case, this knowledge affirms how important fires are to prairie ecosystems. The Echinacea Project, through projects like SppBonus, hopes to further elucidate these mechanisms through which fire improves prairie health.
Until next time!
Sam
Citations:
Wagenius, S. and Lyon, S. P. (2010), Reproduction of Echinacea angustifolia in fragmented prairie is pollen-limited but not pollinator-limited. Ecology, 91: 733–742. doi:10.1890/08-1375.1
https://echinaceaproject.org/pub/wageniusAndLyon2010.pdf
Ison, J.L., S. Wagenius, D. Reitz., M.V. Ashley. 2014. Mating between Echinacea angustifolia (Asteraceae) individuals increases with their flowering synchrony and spatial proximity. American Journal of Botany 101: 180-189.
https://echinaceaproject.org/pub/isonEtAl2014.pdf
Hey again Flog,
My name is Sam Hamilton and this is my second post on the Flog. In my first post, I focused on the experimental goals of the SppBonus project, the kind of data we are measuring, and the project’s relevance to understanding reproductive success in fragmented prairie remnants. Today, I will talk about the progress I’ve made, and the methods I’ve used to move this project from seed head to data set.
The first step of this project was to extract the achenes from the seed heads. Flowers of the Aster family, including Echinacea, are compound flowers, many flowers that grow together to look like one large flower. In Echinacea, each of these flowers, regardless of whether it is pollinated or not, produces a fruit called an achene. By measuring how many achenes contain seeds, we can estimate how well a flower was pollinated in a given year. Thus, in a project like SppBonus, the first step is to extract the seeds from the seed head. The SppBonus data set contained 32 different seed heads, which took me roughly a month to completely clean and organize into samples taken from the top, middle, and bottom of each flower.
The second step is to scan all the gathered achenes so that we can count the total number of achenes. This is an important metric to measure the reproductive fitness of each Echinacea plant. This was a fairly fast process and it only took me three days to scan the achenes from each seed head.
The third step is randomization. We ultimately determine whether or not an achene contains a seed by X-ray. However, there are simply too many seeds to X-ray them all efficiently. Thus, we take a sample from our seeds, X-ray those, and then use that data to make assumptions about the seed set as a whole. We randomize our samples, to ensure our samples are representative of their populations. Without this step, we risk choosing achenes that are the easiest to count, or best fit our expectations of what the data will look like. Our randomization procedure involves pouring the seeds onto a grid where each cell is assigned a letter and a number. A second sheet has these letter and number combinations in a random order and we go down the list selecting from each cell until we’ve collected thirty achenes total. This is the part of the project I’m working on now!
When not working on SppBonus, I am spending my time reading and discussing papers about fire and its effects on pollination and germination with Stuart, Amy, and Scott. I learn a lot from listening, and it’s always interesting to hear their insights into the merits and flaws of each paper, as well as to watch them design new experiments from the ground up.
Hopefully I didn’t bore you, until next time!
Sam
Hey Flog!
My name is Sam Hamilton, and I am a Northwestern senior doing research in the Echinacea Project lab this quarter. My project specifically seeks to understand the relationship between prairie fires and reproductive success of flowering plants using our model organism A. Echinacea. This is an important relationship to understand because, while historically fires were an integral part of the prairie life cycle, today’s isolated prairie remnants are often never burned. This could have a large impact on the success of shorter plants that rely on the extra sunlight and nutrients that a burn year supplies to flower and germinate. This quarter, I will be collecting the data from seed heads collected this year and analyzing it along with data collected in previous years to draw my conclusions.
I am also looking at the reproductive success of Echinacea flowers collected from the bottom, middle, and top of each head. In Echinacea, flowers mature first at the bottom and slowly develop towards the top over time. This allows us us to deduce when a plant was pollinated best during the season. I’ve been hard at work the past month cleaning seed heads and separating their achenes into top, middle, and bottom sections for later analysis. It’s been a lot of work, but the great company has kept it fun!
Until next time!
-Sam
Myself with Susie, Char, Aldo, and Scott. (Left to Right)
One month of cleaned and organized achenes.
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