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Cecropia and ants

While ants are numerous sidekicks in just about every habitat I've explored, these insects are main characters in Monteverde ecology.  Stay tuned for a post about the most obvious Costa Rican ants --- leaf-cutter ants --- in the near future.  For now, I want to share the story of the most fascinating case of symbiosis I've ever seen.

The common Cecropia found in open areas all around Monteverde is home to a three way mutualism that benefits the tree, the ants, and the mealybugs farmed by the ants.  At first, the tree does most of the work, providing hollows within its trunk for an ant colony to move into, then feeding the ants with nutrient-rich Mullerian bodies attached to the petioles of its leaves.

The Azteca ants never leave the Cecropia tree once they move in, so they farm mealybugs to round out their diet.  The mealybugs feed on the phloem of the Cecropia and the ants lap up the honeydew from the mealybugs, so in a way the tree is still providing for the ants, albeit secondhand.

But once an ant colony becomes established, the tables turn and the partnership becomes more equal.  With their food and housing provided, Azteca ants have plenty of time on their hands to protect their host tree.  The ants quickly chew through vines that try to climb up the Cecropia's trunk, and they destroy epiphytes sprouting on the tree's branches.  Azteca ants also attack and drive away herbivores nibbling on the tree's leaves, especially the devastating leaf-cutter ants I'll write about soon.  Although less obvious to the lay observer, Cecropia's pet ants even feed the tree --- the frass they leave behind in the center of the trunk is sucked up by the Cecropia and provides 93% of the tree's nitrogen intake.

In fact, when scientists add up the pluses and minuses of the interaction, the disadvantages are few and all three species come out winners.  In nature, real symbiosis is rare, but the Cecropia-Azteca-mealybug story seems to be a tale of true partnership.

Although we felt lucky to be able to take part in a ready-made community during our stay in Monteverde, I sometimes felt like I wasn't holding up my side of the bargain.  If I had been an Azteca ant, the Monteverde Cecropia probably would have kicked me out as not worth its while.

5-5-01
Today was a pretty bad day.  Well it's only 3:30, but if the day is not quite over, it ought to be.

First came Meeting.  Tyse (our neighbor's dog) has broken loose, with chain trailing, and followed us there, despite me yelling at him.  He whined and barked during Meeting so that a lady went out and sat with him the whole time, which made me feel horrible.  Then, during announcements, he started up again, and I took him home.

It was also potluck day, and I had made a pudding.  The dessert gelled last night, but by the time I got it to Meeting, the dish looked horrible, and of course no one ate it.

The day left me feeling like I have nothing to contribute to the community --- all I do is cause problems.