2016 update: Common garden experiment–1996 cohort

We observed that 95% surviving members of the 1996 cohort were basal in 2016

The oldest Echinacea plants in experimental plot 1 are 20 years old. They are part of a cohort planted in 1996 in a common garden experiment designed to study differences in fitness and life history characteristics of remnant populations. Stuart sampled about 650 seeds (achenes) from eight remnant populations in and near Solem Township, representing the range of modern prairie habitat from small patches along roadsides to a large nature preserve. In 1996, he transplanted seedlings on a 1m x 1m grid, randomly assigning the location of each individual.

Every year, members of Team Echinacea assess survival and measure plant growth and fitness traits including plant status (i.e. if it is flowering or basal), plant height, leaf count, and number of flowering heads. We harvest all flowering heads in the fall and obtain their achene count and seed set in the lab.

Only 15 plants from the 1996 cohort were flowering this year. We were very curious to know if this small number was a result of a low rate of flowering or due to high mortality in the cohort. We found that of the original 650 individuals, 291 were alive in 2016, only 13 fewer than last year. That means only 5% of living individuals flowered. In contrast, 45% of living plants flowered last year (and 37% in 2014, 34% in 2013, 40% in 2012). We’re not sure why so few plants flowered this year; it’s possible that individuals flower less as they age, but we also observed low rates of flowering in younger cohorts in experimental plot 1, suggesting that environmental factors may also be responsible.

Start year: 1996

Location: Experimental plot 1

Overlaps with: phenology in experimental plots, qGen3, pollen addition/exclusion

Physical specimens:

• We harvested all 17 heads and at present they await processing at the lab to find their achene count and seed set.

Data collected:

• We used Visors to collect plant growth and fitness traits—plant status, height, leaf count, number of flowering heads, presence of insects—and it has been added to the database (?)
• We used Visors to collect flowering phenology data—start and end date of flowering for all individual heads—which is ready to be added to the exPt1 phenology dataset
• Eventually, we will have achene count and seed set data for all flowering plants (stay tuned)

Products:

• See the exPt1 core dataset where yrPlanted == ‘1996’ for 1996 cohort fitness measurements

You can find more information about the 1996 cohort and links to previous flog posts regarding this experiment at the background page for the experiment.