LL Cool Joe started an interesting meme a couple weeks ago and Leo tagged me.

The rules:

1. You’ve got to post a link from the person who tagged you.
2. List 8 things that you know about on your chosen subject. You get to choose the subject.
3. You don’t have to tag anyone but you can if you want. If you do, let them know on their blog that they’ve been tagged.
4. List the rules.

Leo gave some awesome tips on baking light bread, and I considered telling you about cornbread or cookies, but, inspired by my plant chemical ecology seminar this week, I’ve decided to share some interesting ecological tidbits instead.  While most people are somewhat aware of the interconnectedness of our world, most people miss out on all the fantastic details.

1. Fruit flies are not very common in the desert because they like a lot of water.  A few species in the Sonoran, however, survive on rotting cacti.  Cacti generally produce lots and lots of nasty chemicals and different cacti produce different nasty chemicals.  Each species of fruit fly can only handle certain nasty chemicals.  The fruit flies figure out which cacti have the right nasty chemicals by smell – but not the smell of the cactus.  Each kind of cactus has its own unique community of microbes that produces its own unique smelly chemicals that the flies recognize.
   Fogleman, J. (2001). Chemical Interactions in the Cactus-Microorganism-Drosophila Model System of the Sonoran Desert Integrative and Comparative Biology, 41 (4), 877-889 DOI: 10.1093/icb/41.4.877
2. Maculinea butterfly caterpillar skins “smell” like ant larvae, so when an ant stumbles across one of these caterpillars it’s like “OMG MY BABY ISN’T IN THE NEST” and takes it home and feeds it at the expense of actual ant larvae. Nash, D., Als, T., Maile, R., Jones, G., & Boomsma, J. (2008). A Mosaic of Chemical Coevolution in a Large Blue Butterfly Science, 319 (5859), 88-90 DOI: 10.1126/science.1149180
3. As carbon dioxide increases in the atmosphere, many plants end up with a higher carbon (sugar) to nitrogen (protein) ratio.  This is bad news for the herbivores because there’s already way more sugar than protein in plants and the herbivores need protein badly.  When the carbon to nitrogen ratio goes up, herbivores often have to eat more and take longer to develop.  This eventually leads to fewer herbivores: Since they’re around longer, they are eaten more often by their predators. Since they have to eat more to get enough protein, they ingest more of the toxins plants produce – and plants can produce more toxins because of the extra carbon.  And since there’s so much more sugar than protein, the herbivores can starve to death – a candy diet wouldn’t work out so well for you either.
   

   Scrub Oaks And Sky, Grayton Beach State Park, FL 2008 by Lone Cypress

   STILING, P., & CORNELISSEN, T. (2007). How does elevated carbon dioxide (CO) affect plant–herbivore interactions? A field experiment and meta-analysis of CO-mediated changes on plant chemistry and herbivore performance. Global Change Biology, 13 (9), 1823-1842 DOI: 10.1111/j.1365-2486.2007.01392.x

4. Mycorrhizae are a mutualism between plants and fungi.  The plant provides the fungus with carbohydrates and the fungus helps the plant get nutrients from the soil, like nitrogen.  Plants make carbohydrates from carbon dioxide and sunlight and their growth is usually limited by nitrogen.  While fungi can absorb nitrogen and phosphorus from the soil, they can’t make their own carbohydrates.  Elevated levels of atmospheric carbon dioxide help the plant grow more, but also mean that the plant requires more nitrogen.  So, if carbon dioxide is higher, the plant gives away more carbohydrates to the fungi in exchange for more nitrogen.  Remember, though, that the fungi need nitrogen, too.  Some species of mycorrhizae grow so much when the plant is exposed to elevated levels of carbon dixoide that it uses up all of the nitrogen instead of giving it to the plant – not only does it steal the carbohydrates the plant makes, it takes up all the soil nutrients the plant needs.
   

   Mycorrhizae

   ALBERTON, O., & KUYPER, T. (2009). Ectomycorrhizal fungi associated with seedlings respond differently to increased carbon and nitrogen availability: implications for ecosystem responses to global change.  Global Change Biology, 15 (1), 166-175 DOI: 10.1111/j.1365-2486.2008.01714.x

5. Even if the soil is wet, a plant can still be too dry, especially if it’s cold outside.  When water is cold it becomes more viscous.  You may not notice that cold water is thicker than warm water, but to a plant it’s the difference between milk and a milkshake.

   Lopushinsky, W, & Kaufmann, M (1984). Effects of Cold Soil on Water Relations and Spring Growth of Douglas-fir Seedlings

6. Plants use long dead cells to transport water.  You can think of a bunch of them together like a bunch of tiny connected pipes.  Water is not pushed through the pipes from the ground (with a positive pressure)– it is pulled through the plant like water through a straw (with a negative pressure).  Transpiration – the evaporation of water from the leaves – is what pulls water through the plant.  This is only possible because water has a very strong tensile strength.  Water molecules tend to cling to one another very tightly so that in a plant, there is a column of water from the roots to the leaves that is stretched like a rubber band.
   

   Water conducting cells in plants

   Dixon, & Joly (1894). On the ascent of sap Annals of Botany

7. The system plants use to get water works pretty well, but there can be some pretty serious problems.  Plants basically suck water from the soil.  When the soil is dry, they suck harder.  Sometimes they suck so hard that air comes through the sides of the water conducting cells.  Once air gets in, it expands and fills up the cell and “breaks” the column of water.  This is called cavitation.  Since there are lots of these cells and lots of little water columns, this isn’t usually a big deal, but if it happens too often, the plant can die.  Different plants experience cavitation at different levels of water stress.  I study pinyon pine trees that grow with juniper trees.  Pinyon pine water conducting cells cavitate in much “wetter” soils than juniper.  For example, these two pictures show a pinyon juniper woodland at two points in a particularly dry year.  In the first picture, you see both pinyon and juniper.  In the second picture, almost all of the living trees are juniper.
   

   Pinyon-Juniper Woodland

   

   Juniper woodland

   Linton, M., Sperry, J., & Williams, D. (1998). Limits to water transport in Juniperus osteosperma and Pinus edulis: implications for drought tolerance and regulation of transpiration Functional Ecology, 12 (6), 906-911 DOI: 10.1046/j.1365-2435.1998.00275.x

8. The world is complicated: there are countless interactions between organisms and predictions can be nearly impossible.  What we are sure of is that people are changing the climate very quickly and our ecosystems are also changing in ways that will very likely have terrible consequences for us and other species.  I study ecology not just because it’s beautiful and fascinating, but also because it may give us the information we need to live better in the world.

I’ll tag Brooke, Lights, Carpe Omnis, Eugenie, Transient Theorist, Karina, and FreedomGirl.