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 48 natural occupancy DHJanzen100130.jpg high resolution
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In the same old field described above, there were some dead (above ground) ant-acacias that had a single (or two) large healthy stump sprouts with beautiful large perfect leaves, large thorns, and were adding 1-2 cm of height every 1-2 days. Why? A small amount of search revealed that the fire had been hot enough to kill many ant colonies (or at least their queens) but not all. In those cases where there was an ant colony in the dead (above ground) ant-acacia, it had simply moved back into the stump sprout and its massive worker force protected it from all comers. Now, a naturally occurring experiment of this nature appears to be perfect to demonstrate that the ants protect the plants (and that the ants require the plant and its products for survival is easily demonstrated by killing the ant-acacia after which the ant colony gradually starves to death and dwindles as it frantically searches for other ant-acacias). However, the total skeptic can argue that no, in this particular case the few surviving ant colonies simply moved around the site until they found the few ant-acacias that were growing exceptionally well (for whatever soil, moisture and sun reasons) and moved into them. Correlation does not prove causation. A true manipulative experiment is indeed called for. |
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