Shooting Star Goals

When the move to Illinois was finalized I set a goal for this spring. It is always good to have goals and mine was to see a large population of shooting stars. I am, of course, not talking about the ones from outer space but rather plants of the genus Dodecatheon. Various nature centers in this region boast lovely photos of hillsides covered in them. Except for my time in Wyoming where Dodecatheon conjugens often kept me preoccupied on hikes, I have only seen Dodecatheon as a spattering of individuals. This past weekend I met my goal. 

We were hiking up a wooded hillside when I noticed a few rosettes of fleshy, light green leaves. This is where having a search image comes in handy. There was no mistaking these plants. At first it seemed as if we were meeting a bit too early. I could just make out some flower buds poking up from the middle of the rosette. However, further up on the ridge, a warmer microclimate rewarded us with quite the display. All along the sun-streaked hillside were hundreds of shooting stars just starting to bloom. What's more, these were a unique species of shooting star I had never seen before. 

Dodecatheon frenchii is as Midwestern as it gets for this genus. This particular species is known from only six states. It prefers to grow in shallow sandy soils along the southern edge of the glacial boundary. Often times it can be found at the base of sandstone cliffs and ledges. Taxonomically speaking, this species is quite interesting. It is very similar to D. meadia. In fact, some authors lump them together. The greatest difference between these plants, however, lies in their chromosomes as well as their habitat preferences. D. frenchii is diploid and is a sandstone endemic, whereas D. meadia is tetraploid and much more widespread. 

Despite their limited range, D. frenchii are quite hardy. Growing in sandy soil has its challenges. The biggest issue plants face is drought. When summer really heats up, these plants go dormant. Their thick roots store water and nutrients to fuel their growth the following year. Due to the nature of their preferred habitat, few other plants can be found growing with D. frenchii. That's not to say nothing can, however, competition is minimal. As such, D. frenchii does not compete well with other plants, which certainly sets limits on its preferred habitat. Like all members of this genus, D. frenchii flowers are adapted for buzz pollination. Certain bees, when landing on the downward pointing stamens, vibrate their bodies at a special frequency that causes pollen to be released.

Seeing these plants in person lived up to all of the hype. It was one of those botanizing moments I will never forget. Although I often go outside with the simple goal of just being in nature, sometimes having a specific mindset makes for a fun adventure. If anything, it makes for some great bonfire stories. So here's to spring and to Dodecatheon and to just getting outside. 

Further Reading:
http://bit.ly/1U69kj1

http://bit.ly/1rht7Bl

Ploidy and Pollinators

Polyploidy (having more than two sets of chromosomes) has allowed plants to do some incredible things from an evolutionary perspective. It is now widely believed that polyploidy has played a role in the evolution of 45% - 70% of the flowering plants we know and love today. Having extra sets of chromosomes allows mutations to occur without harming important cellular processes. Despite this knowledge, very little has been done to investigate exactly how polyploidy manifests in terms of ecological interactions. Recently, however, research into this has unveiled some very interesting ways in which polyploidy may lead to speciation. One of these has to do with pollination.

You are probably more familiar with the effects of polyploidy in plants that you realize. Polyploid plants are often much larger and more robust than their diploid relatives and many of the horticultural species we plant in our gardens have been bred for this genetic quirk. Polyploids happen in nature as well and it has long been known that polyploid populations often naturally segregate themselves out in the wild. This has led to observations that polyploid plants are often more resistant to things like parasites and herbivores. Recently, researchers from the University of California, Santa Cruz took a look at diploid and polyploid populations of a plant called Heuchera grossulariifolia.

They wanted to see if naturally occurring populations of each experienced differences in pollinators. After observing flower visitation rates between each population, they found some surprising differences. Diploid plants were more often visited by small bees in the genus Lasioglossum whereas the polyploid populations were more often visited by bumblebees (genus Bombus). Though this may seem inconsequential, differences in pollinators can have huge effects on reproduction.

If different pollinators are visiting these separate populations then they are essentially reproductively isolated from each other. With little to no gene transfer between diploids and polyploids, each population may follow its own evolutionary trajectory. This very well could lead to speciation. How pollinators distinguish between the populations is not yet known. There are some morphological differences, however, subtle differences in chemical cues may also play a role. Either way, research like this is opening up some exciting new avenues for investigation.

Photo Credit: Paul Slichter (http://bit.ly/1IDFVo3) and Science and Plants for Schools (http://bit.ly/1yQykCu)

Further Research:
http://www.ncbi.nlm.nih.gov/pubmed/18724730