Small remnant Echinacea populations may suffer from
inbreeding depression. To assess whether gene flow (in the form of pollen) from
another population could “rescue” these populations from inbreeding depression,
we hand pollinated Echinacea from six different prairie remnants with pollen
from a large prairie remnant (Staffanson Prairie) and from a relatively small
population that we call “Northwest Landfill.” We also performed
within-population crosses as a control. Amy Dykstra planted achenes (seeds)
that resulted from these crosses in an experimental plot at Hegg Lake WMA.
Plants in the crossing plots were originally found as seedlings like this one
We sowed a total of 15,491 achenes in 2008. 449 of these
achenes germinated and emerged as seedlings. Each summer we census the
surviving plants and measure them. This summer we found 48 surviving plants.
None of these plants has flowered, but we think some of them are close! The
largest plant we measured had 4 leaves, the longest of which was 35 cm.
You can read more about the interpopulation crosses, as well as links to prior flog entries mentioning the experiment, on the background page for this experiment.
Start year: 2008
Location: Hegg
Lake WMA
Data collected: Plant
fitness measurements (plant status, number of rosettes, number of leaves, and
length of longest leaf), and notes about herbivory. Contact Amy Dykstra to
access this data.
Products: Dykstra, A. B. 2013. Seedling recruitment in fragmented populations of Echinacea angustifolia. Ph.D. Dissertation. University of Minnesota. PDF
Today Brad and I finished the 2015 census on my crossing experiment plot.
The plants in this plot are the offspring of within-population or between-population crosses of Echinacea plants from six nearby prairie remnants. In most cases, the pollen for between-population crosses was supplied by the largest prairie remnant in the experiment, identified as SPP in the figure below. Crosses were made in the summer of 2008 (thanks to LOTS of help from Team Echinacea). We sowed a total of 15,491 achenes into this plot in the fall of 2008. We estimated that about 40% of the achenes contained embryos, based on their weights.
In the spring of 2009, we found 396 seedlings. We found an additional 43 seedlings in late summer, 2009, and another 10 new seedlings in the summer of 2010. In 2011, we were only able to find 264 of these plants, and the numbers have continued to decline: we found 185 in 2012, 124 in 2013, 112 in 2014, and 89 this summer (2015). We have yet to observe any flowering!
As you can see from the graph (based on results through 2011), results of within- and between-population crosses have been mixed. The columns in the graph represent estimated mean total leaf number for each cross, for a starting number of 25 achenes, based on an analysis of total fitness (using an aster model). The main effect of cross type was non-significant; however, there was a significant effect of maternal population, and a statistically significant interaction between maternal population and cross type. In other words, the success of the type of cross depended on the maternal plants that were crossed. For the smallest population (identified as NWLF), offspring of between-population crosses outperformed within-population crosses. For the largest population (SPP), the within-population crosses performed better than the between-population crosses.
What implications can we draw from these results? In some cases a small, inbred remnant population may be enhanced by cross-breeding with another local population (this is called “genetic rescue”). However, between-population crosses also run the risk of outbreeding depression, as we have observed for the SPP-Lf cross, compared to the SPP-SPP within-population cross.
We now have 4 more years of data, with quite a bit of mortality. It will be exciting to perform another analysis including more data!
Thanks to some critical help from Team Echinacea, we were able to complete the 2015 census on the local adaptation experiment this week. We found a total of 282 live Echinacea plants this summer (compared to 372 in 2014). 96 of the survivors live in the western South Dakota plot, and 186 in the Hegg Lake plot. None of the plants have yet flowered, though some of the western SoDak plants seem to be large enough (see photo). Maybe next year!
Hello! I’m Amy Dykstra, and I will be participating with the Echinacea project part time this summer, beginning sometime after June 18.
I have been involved with the project since 2006, and am looking forward to meeting this year’s Team Echinacea!
On Thursday, 23 May 2013, Brad Dykstra and I (Amy Dykstra) helped Stuart and his parents burn the common garden (C1). The burn was slow and thorough. Some photos follow. We started at the south end of the plot.
At times, the fire was quite smokey.
Here, Stuart lights vegetation in the ditch along the west side of C1.
This afternoon, Amber E. and I (others joined in later) started organizing the data sheets from the seedling searches we have completed so far this season. We are sorting the new maps and other data sheets for each site by focal plant number, and adding the new pages to the end of each site’s notebook. As we organize data sheets for each site, we are also reconciling the maps with the master data sheet for each site.
The data we have recorded on the frame data sheets will need to be entered into a spreadsheet, so that we can use the measurements to generate maps and distance matrices for those focal plants.
slingDataEntryBlank.xls
Here’s an Excel file we can use to do the data entry. For each frame data sheet, 2 people should enter the data. The first person will enter data in the DE_1 worksheet, and the second person will enter data in the DE_2 worksheet. The check columns in DE_1 will then allow us to check for data entry errors. The file should be saved as “slingDataEntry2011Page[page number]”.
I’ll put together a master list with all the frame data sheet page numbers. The frame data sheets will be in the seedling notebooks. People will enter their initials when they have completed data entry for a page number.
Let me know if you have suggestions to make the data entry work better.
Today we started the seedling search at Steven’s Approach (SAP). The wind was strong and air temperature was chilly. We searched 3 circles; in one of the circles we found 6 seedlings! We drew a map and filled in a matrix, as we have done in previous years. We also tried out the new coordinate frame.
I (Amy) have revised the protocol. Please read it and feel free to suggest ways it can be improved. Seedling Search Protocol 2011.doc
Yesterday we burned the common garden. There was a lot of fuel, since the common garden was last burned in May 2008. It was a slow, even burn.
Stuart lighting the fire, at the northeast corner of the common garden.
Click on the thumbnail image to see a larger picture.
Second photo: We doused the back fire with water, allowing the head fire to proceed west-ward across the common garden.
Third photo: View from the northeast, looking southwest. The dark green in the foreground has already burned.
Fourth photo: View from the northwest. It was a good burn!
Kate and I have had some beautiful weather for field work (except today–it rained most of the day). Here’s a picture of the roadside site we call East Riley. Notice that our ambitious mower has mowed TWO swaths of the roadside. The mowed area includes most of the circles I am searching to re-find and measure plants we had identified in years past.
We do seedling searches every spring at 14 prairie remnants. We search within 41 cm (or 50 cm for smaller populations) of randomly selected Echinacea plants that flowered the previous summer. Since 2006 we have used these spring searches to find new seedlings (identifiable by the presence of cotyledons). When we find seedlings, we draw circle maps showing the seedling locations with respect to the focal plant, and make measurements to other tagged plants. In 2009 and 2010 we mapped ALL Echinacea plants within the 41/50-cm radius circles. Late in the growing season, we return to the 14 sites and re-find the seedlings and other plants. We update the circle maps, and measure the surviving plants.
Why go to all this trouble? I plan to use the data to estimate the growth rate for these small Echinacea populations. Are the Echinacea producing enough offspring to maintain their populations? That’s the question I hope to answer!
The re-finds are complete at eelr, lih, nessman, nwlf, randt, sap, sgc and spp. I am currently working at eri; still remaining are eth, kj’s, lc, lf and ri. Some of the sites are disappointing. There has been a lot of gopher activity at lih, and most of the Echinacea plants, big and small, are gone. I was only able to find 1 of the 12 seedlings we had previously mapped. Other sites (eri, ri, nessman) are disturbed by frequent roadside mowing and scraping. In spite of that, we were able to find 18 of the 23 previously identified seedlings at nessman. In total (so far), we have found 54/85 seedlings. Some of the survivors were first identified in 2007 (I don’t think I’ve found any 2006 seedlings yet–but there weren’t many to begin with).
I’ll post an update when I finish entering all the data…or the next time I get rained out!
