Dear Flog,
Last time I mentioned in passing that Stuart, Amy, Scott, and I had been discussing papers about fire and its potential impact on the reproductive fitness on Echinacea plants. This week I will go into greater detail about what I’ve learned about fire and what our data can teach us about how it impacts prairie health.
Some of our studies taken from previous years have shown us that, even when there are enough bees to carry pollen from plant to plant, Echinacea plants can have difficulties receiving pollen from potential mates. There are a few reasons for this. In our fragmented prairie remnants, Echinacea plants are often far enough apart that pollen collected by a bee will often fall off before it can reach another Echinacea flower. Echinacea plants may also flower in different years, or at different times in the season. This can prevent mating even between close flowers. This mate availability problem is compounded by the fact that Echinacea is self-incompatible, meaning a plant cannot pollinate itself or its close relatives. This means that if a plant flowers and fails to find mates, all the energy it expends to flower and fruit results in no offspring. This is an extraordinary energy cost for no payoff.
Data we have collected seems to suggest that fires may help perennial prairie plants like Echinacea find other mates. Explosive flowering after a large burn is typical for prairie plants. There is some evidence that increased availability of nutrients from burned organic matter and the increased availability of sunlight provide resources for a plant to invest in a costly reproductive structure like a flower. This is probably no different for Echinacea. However, as an added bonus, some of our data seems to show that this explosive flowering may reduce the reproductive isolation of Echinacea plants by increasing the number of synchronous flowering plants. Thus, fire helps Echinacea successfully seed by increasing the number of available mates. Really cool!
The tendency of Echinacea to flower synchronously after a fire could be the result of natural selection, or simply a byproduct of the excellent growing conditions created by fire. In either case, this knowledge affirms how important fires are to prairie ecosystems. The Echinacea Project, through projects like SppBonus, hopes to further elucidate these mechanisms through which fire improves prairie health.
Until next time!
Sam
Citations:
Wagenius, S. and Lyon, S. P. (2010), Reproduction of Echinacea angustifolia in fragmented prairie is pollen-limited but not pollinator-limited. Ecology, 91: 733–742. doi:10.1890/08-1375.1
https://echinaceaproject.org/pub/wageniusAndLyon2010.pdf
Ison, J.L., S. Wagenius, D. Reitz., M.V. Ashley. 2014. Mating between Echinacea angustifolia (Asteraceae) individuals increases with their flowering synchrony and spatial proximity. American Journal of Botany 101: 180-189.
https://echinaceaproject.org/pub/isonEtAl2014.pdf
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