2019 Update: Echinacea Ploidy

To see how ploidy varies in Echinacea species in our study site, in fall 2019, wecollected and dried tissue from E. pallida, E. angustifolia, and E. purpurea. We also collected tissue from potential hybrids and known hybrids. We brought the dried tissue back to the Chicago Botanic Garden, where we plan to analyze ploidy using a flow cytometer, a device that can be used to find relative genome size.

The flow cytometer used to assess relative genome size. Although it just looks like a box, it is truly a powerful machine.
Example of dried Echinacea tissue… We thought it might be a hybrid when we visited it in the field!

Unfortunately, preparing samples for the flow cytometer is difficult, so we are going to first optimize our Echinacea tissue preparation protocol using live tissue. To do this, we withdrew accessions of E. angustifolia, E. pallida, and E. purpurea from Millennium Seed Bank at the CBG. For E. pallida, we took seed from collections throughout its range to see if its ploidy varies with latitude. We are currently germinating this live tissue to use for ploidy analysis with Elif. We are very excited to see what we find – any finding will help expand genomic knowledge for the genus Echinacea!

Start year: 2019

Location: Hegg Lake WMA, various prairie remnants and restorations, hybrid experimental plots

Overlaps with: Echinacea hybrids (exPt6, exPt7, exPt9), Echinacea pallida flowering phenology

Data/ materials collected: Dried tissue from plants throughout the study area; samples are currently held at Chicago Botanic Garden, in a small box in the glass cupboard to the right upon entering room 159, the Population Biology Lab. Updates will be posted when genome data is available.

Background: If you’d like to learn more about this experiment, check out the background flog post!

Ploidy Project Overview and Background

Echinacea angustifolia is the only species of Echinacea native to Minnesota, but it is not the only Echinacea species that currently inhabits MN. In the Echinacea Project study area, there are actually three different Echinacea species: E. angustifolia, E. pallida, and E. purpurea. Both non-native species were introduced in restorations from seed that was not locally sourced. We know that non-natives hybridize with our native Echinacea, and we fear that introgression with hybrids may result in genetic swamping of E. angustifolia. We want to learn as much as we can about similarities and differences between Echinacea species in MN so we can assess the threat level of non-native Echinacea in Solem Township and take the proper steps to alleviate the potential threat.

There have been reports that ploidy level varies among Echinacea species (McGregor 1968; McKeown 1999). Specifically, E. pallida is reportedly tetraploid (4n) throughout most of its range, while E. angustifolia and E. purpurea are diploid (2n). There are also reports of E. angustifolia in Oklahoma and Texas being tetraploid (this is a different variety of E. angustifolia from the one we study). Nonetheless, we are interested in the ploidy of Echinacea in MN because it affects whether hybrids are able to reproduce. If a diploid mates with a tetraploid, it produces triploid (3n) offspring; triploids are generally not fertile. Thus, ploidy of non-natives greatly affects the ability of non-native Echinacea to genetically swamp E. angustifolia by creating fertile hybrids.

E. pallida head – the flowering heads are distinguishable by pollen color and ray floret color/length.
E. angustifolia head

To investigate ploidy differences between Echinacea species in Minnesota, we will collect and dry tissue from the three different Echinacea species and their hybrids and assess relative genome size using a flow cytometer at the Chicago Botanic Garden. We will also assess relative genome size in seedlings grown from seeds sourced from various latitudes in our species’ ranges to see if the individual species vary in ploidy level throughout their range.

This is the flow cytometer – the machine used to assess relative genome size at the CBG.