In summer 2022, I continued the interremnant crosses experiment to understand how the distance between plants in space and their timing of flowering influences the fitness of their offspring. This experiment builds on my study of gene flow and pollen movement in the remnants, asking the question of how pollen movement patterns affect offspring establishment and fitness. If plants that are located close together or flower at the same time are closely related, their offspring might be more closely related and inbred, and have lower fitness than plants that are far apart and/or flower more asynchronously. In other words, if distance in space or time is correlated with relatedness, we’d expect mating between more distant or asynchronous individuals to result in more fit offspring.
To test this hypothesis, I performed crosses between plants across a range of spatial isolation (within the same population, in adjacent populations, and in far-apart populations) in 2020. With the team’s help, I also kept track of the individuals’ flowering time to assess whether reproductive synchrony is associated with reduced offspring fitness, suggesting that individuals that flower at the same time are more closely related.
In 2021, I repeated the same hand crossing methods to assess the fitness consequences of outcrossing on 44 focal plants. However, instead of planting the offspring from these crosses as seeds, I germinated them in the growth chamber and transferred sprouts to a plug tray.
In spring 2022, with help from the team, I planted the seedlings as plugs into ExPt1. I measured the seedlings throughout the summer.
Lindsey digs a hole for an Echinacea plugA baby Echinacea!Amy plants Echinacea in ExPt1 after the burn
To learn more about Amy’s project, check out this video created by 2021 RET participant Alex Wicker.
Start year: 2020
Location: On27, SGC, GC, NGC, EELR, KJ, NNWLF, NWLF, LF
Data collected: Style shriveling and seed set and weight from crosses, start and end date of flowering, coordinates of all individuals in the populations listed above. Leaf count and height of seedlings at three points during the summer (two weeks after planting, mid-summer, and late summer).
On Friday, grad student Amy W. paid a visit to the lab at the Chicago Botanic Garden to x-ray Echinacea achenes for several of her projects including the Dust Project, interremnant crosses, and gene flow experiments. We’re thrilled to have a functional x-ray machine once again. Amy noticed lots of variation in her samples, so we’re excited to learn about seed set for these experiments!
In summer 2021, Amy Waananen continued the interremnant crosses experiment to understand how the distance between plants in space and in their timing of flowering influences the fitness of their offspring. This experiment builds on Amy’s study of gene flow and pollen movement in the remnants, asking the question of how pollen movement patterns affect offspring establishment and fitness. If plants that are located close together or flower at the same time are closely related, their offspring might be more closely related and inbred, and have lower fitness than plants that are far apart and/or flower more asynchronously. In other words, if distance in space or time is correlated with relatedness, we’d expect mating between more distant or asynchronous individuals to result in more fit offspring.
To test this hypothesis, Amy performed crosses between plants across a range of spatial isolation (within the same population, in adjacent populations, and in far-apart populations) in 2020. With the team’s help, she also kept track of the individuals’ flowering time to assess whether reproductive synchrony is associated with reduced offspring fitness, suggesting that individuals that flower at the same time are more closely related.
In 2021, Amy repeated the same hand crossing methods to assess the fitness consequences of outcrossing, this year on 44 focal plants.
To learn more about Amy’s project, check out this video created by RET participant Alex Wicker.
Amy collects pollen from Echinacea anthers
Start year: 2020
Location: On27, SGC, GC, NGC, EELR, KJ, NNWLF, NWLF, LF
Data/Materials collected: Style shriveling and seed set and weight from crosses, start and end date of flowering, coordinates of all individuals in the populations listed above
This summer I started a new experiment to understand how the distance between plants in space and in their timing of flowering influences the fitness of their offspring. This experiment builds on my study of gene flow and pollen movement in the remnants, asking the question of how pollen movement patterns affect offspring establishment and fitness. If plants that are located close together or flower at the same time are closely related, their offspring might be more closely related and inbred, and have lower fitness than plants that are far apart and/or flower more asynchronously. In other words, if distance in space or time is correlated with relatedness, we’d expect mating between more distant or asynchronous individuals to result in more fit offspring.
To test this hypothesis, I performed crosses between plants across a range of spatial isolation (within the same population, in adjacent populations, and in far-apart populations). With the team’s help, I also kept track of the individuals flowering time so that I can assess whether reproductive synchrony is associated with reduced offspring fitness, suggesting that individuals that flower at the same time are more closely related.
I ended up using 42 focal plants (two of which were mowed before I could harvest them) and a total of 167 sires. I planted 359 offspring from these crosses in November. Next spring and summer, I will measure the seedlings to collect data on emergence and growth. Seed set was lower than I wanted it to be (only ~20%, when I would have expected 60-70% based on compatibility rates in the remnants), so I will also likely perform more crosses in summer 2021 to shore up my sample size.
Crossing at scenic On 27
Start year: 2020
Location: On27, SGC, GC, NGC, EELR, KJ, NNWLF, NWLF, LF
Data/Materials collected: 40 seedheads, style shriveling and seed set and weight from crosses, start and end date of flowering, coordinates of all individuals in the populations listed above
Products: I planted the seeds from the crosses in a plot adjacent to P1 in November, as detailed in this flog post.
This past Friday I planted the seeds from the inter-remnant crossing experiment I completed over the summer. The goal of this experiment is to understand how the distance between plants that live in little fragmented remnants and the difference in their timing of flowering influences the fitness of their offspring. The expectation is that if plants that are close together and/or flowering at the same time are closely related, their offspring might be more closely related (i.e., inbred) and have lower fitness than plants that are far apart and/or flowering more asynchronously. If this is true, then it would suggest that individuals in small, fragmented habitats would benefit from reaching more distant or dissimilar mates, such as by introducing seeds from faraway populations to remnants, creating corridors that promote pollinator movement, or managing habitat to increase heterogeneity in flowering time.
Plot location & layout:
The plot is located directly to the east of P1, spanning 12 m east to west and 30 m north to south, between positions 860 and 890. See Mia’s flog post from September for more information about how we prepared the plot by clipping the grass and treating the sumac with Garlon. Mia also used Darwin to shoot points within and along the edges of P1 so that I could generate coordinates for each position in my planting that aligned with P1’s crooked grid. This was a good exercise in geometry. I figured it out, but not before googling how to find the intersection of two lines. Oh well!
When I laid down the meter tapes based on the end points of the rows in this grid, it matched pretty well (the rows were supposed to be exactly 30 m long), but they were off a bit due to topography and the vegetation keeping the tape from laying perfectly flat. It was right on for row 58 and off by ~5cm in rows 62 and 65. We lined up meter sticks with the flags placed ever two meters and positioned achenes relative to according to the flag positions, rather than the tape. We placed 4 achenes per meter in positions 860-889.75.
Randomization:
Based on the number of seeds I had, and the expectation that I might want to plant more for this experiment in the future, I randomly chose three rows (58, 62, and 65) to plant out of the twelve total rows that fit in the area that we prepared. I randomly assigned positions to all of the full achenes, based on their weight. Prior to planting, I placed each of these achenes into a 1.5mL microcentrifuge vial and labeled it with its planting position (1-360). I sorted the vials in order of planting position and placed them in vial trays that we brought into the field.
Planting:
It was a dry and unseasonably warm day. This is lucky because there was 10 inches of snow where the plot is located a week and a half earlier. I was able to convince Matthew and Gooseberry to come along to help. Matthew was extremely helpful, but Goose mostly ate deer poop all day and threw up on the way home. Very yucky! To set up for planting, I staked to the end points for the rows we were planting, set up a meter tape, and then staked to and placed pin flags at positions every two meters along the rows. I started by placing pin flags every meter, but this was time consuming and a pin flag every two meters gave us a sufficient reference point for each meter.
We liked breaking the actual planting into two steps, and working in a pair, because it meant that we had fewer items to fumble around with and it was easy to catch and fix each other’s mistakes, such as accidentally skipping positions. I do not believe we made any actual goofs, which is a first for me with planting! For the first step, one person cleared the duff, and the other placed the corresponding vial. For the second, one person placed the achene and collected the vial, while the other placed the toothpick and carried the clipboard, making any notes, e.g., if the achene was planted a few cm off the row to avoid placing it on a rock or in bunchgrass. The first step took about 10-12 minutes per 50 positions. The second took about 8-10 minutes per 50 positions. We set the achenes on top of the soil so that they had good contact with the soil, but weren’t buried. We finished around 4 PM and were grateful that we did not have to plant in the dark.
I hope the seeds have a good winter and I look forward to seeing them in the spring!
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