Category Archives: Prairie Insects

Photo of the Week – June 15, 2012

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Milkweeds have very distinctive flowers, with unique shapes and features.  I guess it shouldn’t be surprising that their pollination story is equally interesting.

Common milkweed (Asclepias syriaca) flowers. Lincoln Creek Prairie – Aurora, Nebraska.

First, milkweed flowers don’t produce thousands of of individual pollen grains that can each get carried away to other flowers by visiting insects.  Instead, milkweeds have what are called “pollinia”, or waxy masses of pollen that are designed to stick to insects.  You might think that a flower with a specialized pollen structure like that would have a system to make it easy, or even automatic, for any visiting pollinator to pick up and deliver that pollinia to the next flower.  After all, there are countless stories of flower types that facilitate pollination by forcing visiting insects to hit the right spots as they forage for nectar and pollen.

With milkweeds, not so much.

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Quantifying the Value of Plant Diversity

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Why is plant diversity important? 

I can come up with lots of reasons, including the value to pollinators, correlations between plant and insect diversity, and contributions to ecological resilience – among others.   But it’s much more difficult to quantify the specific functional differences between high-diversity and low-diversity prairie plantings.  Even basic questions are difficult – for example, how many plant species does it take to see benefits?

Most of us who spend time in prairies know intuitively that plant diversity is important, but if we’re going to influence environmental policy, agricultural practices, and other large-scale conservation strategies, we’re going to need stronger and more quantified answers than intuition provides us.

In an attempt to help find some of those more specific answers, we have built some research plots within our Platte River Prairies, in which we’ve established prairie plantings of various plant diversity.  Each treatment plot is 3/4 acre (1/3 ha) in size – big enough that we hope to compare patterns of invertebrate species composition and activity,  soil changes, differences in the resistance to invasive species, and more.  We’ve actually established two sets of plots now; one in 2006 and the second in 2010.  The 2006 set consists of low diversity (15 species) and high diversity (100 species) plots, and the 2010 set consists of three treatments: a monoculture of big bluestem, low diversity (mostly grasses, with a few forbs), and high diversity (100 or more plant species).  Each treatment is replicated at least 4 times.

Clint Meyer, of Simpson College (Iowa), was out last week doing some sampling of ground-dwelling invertebrates.  Here he examines insects caught in a pitfall trap within our 2010 diversity research plots.

A close-up view of a vial of insects caught in a pitfall trap. There are least two species of ground beetles in the vial (floaters and sinkers!) as well as springtails (the little specks floating in the lower left hand portion of the vial).

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