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 42 senescence DHJanzen100124.jpg high resolution
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| After growing 12-15-20 years, the ant-acacia dies of (programmed senescence). This 15-year-old individual was cut out of the general vegetation surrounding (and now, overtopping) it and put out against the sky to see it better. Its ratty top is heavily defoliated because its ant colony has died recently (probably of old age, or an accident to the queen). While in theory a founding queen could establish in one of its empty thorns, the queens seem to be genetically programmed not to search in such plants. Equally, a large adult ant-acacia is normally occupied by an ant colony that will set on and kill (sting and dismember) any founding queen that attempts to climb up it. By this stage in development, the ant-acacia will have been reproductive for about 12-15 years. In the dry margins of the ant-acacia distributions, the secondary successional vegetation is lower and not as dense, but ant-acacias are themselves lower, bushier and still die after 12-20 years of growth. Only in Pacific coastal Mexico north of the Rio Balsas Basin (north of Acapulco) has another life style evolved (see satellite images). | ||
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