Continued progress on SppBonus, focusing on methods

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!



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