The main projectsWe investigate Echinacea using three main approaches.
Observations in natural remnant populationsWe have an 12 year demographic record of adult plants in 27 remnants. Each year we census plants to see if they are flowering, alive, or dead. We precisely map the locations of individual plants so we are confident that we are visiting the same plant from year to year. We tag all mapped plants too, but tags seem to disappear at a much greater rate than do the plants.
In addition to basic demographic information, we have observed other natural processes in these remnants for one or several years. Because we have mapped all adult plants in our remnants, we focus on the spatial patterns of ecological and evolutionary processes (including plant-animal interactions) at both individual- and population-based spatial scales. More information on each of these projects will be posted here later:
- Pollen limitation of seed set
- Abundance and diversity of Echinacea pollinators and floral visitors
- Mating compatibility
- Flowering phenology
- Incidence of herbivores on Echinacea
- Ants & aphids on Echinacea
- Influence of prescribed burns on flowering, seed set, and seedling recruitment
Experiments--The Common GardenWe have planted 10,566 seedlings in our main common garden experiment. The first planting was in 1996. These plants comprise three experiments:
1. NAT was designed to assess differentiation among remnant populations.
2. INB1 evaluates effects of inbreeding and interpopulation crossing on progeny fitness.
3. QGVAR estimates genetic components of variance in fitness and other traits.
We plan to include more details on all three of these experiments later.
For all plants in all years, we have measured survival, growth, and reproductive traits. In the 1996 planting cohort of NAT (600 plants), 397 were still alive in 2005. 135 plants (34% of those surviving) flowered in 2005. Seven of these 10-year old plants flowered for the first time in 2005. Another 122 plants remain alive but have not yet flowered.
In spring 2006, we germinated & planted our latest two experiments:
4. INB2. With this experiment we will be able to assess effects of population of origin (e.g. population size) on inbreeding and inter-population mating. We planted about 1500 plants.
5. PHEN. With this experiment we will assess heritability of flowering phenology. We planted about 4000 plants.
Read about what we did in spring 2006 to set up these two experiments.
ModelingIn addition to our empirical efforts, we use modeling approaches to better understand the biological processes that influence plants growing in fragmented habitat. We have one paper that describes a model that we developed to understand how self-incompatibility influences the demography and population persistence of plants in small remnant populations. Self-incompatibility occurs in many prairie plants.
In populations with many plants (and many S-alleles), self-incompatibility keeps related plants from mating, which is good because it reduces inbreeding depression. However, in small remnants we found that many nearby pairs of plants shared the same S-alleles, so ovule fertilization, and thus seed set, was low. We used our computer model to forecast what will happen to these populations in the future. We predict that reduced seed set will cause populations to decline--the smaller the population, the faster the decline. Our model predicts that the number of S-alleles, and thus compatible mates, will decrease over time, causing populations to decline faster. We think the effects we describe in the paper occur frequently in many plants, not just prairie plants, and not just rare plants. We expect detrimental effects to become more severe over time as populations remain isolated.