As exemplified by the relationship between the yucca moth species called "Tegeticula
yuccasella" and the yucca plant species called "Yucca elata," the
biological phenomena of coevolution and mutualism hold special interest for those
involved in the science of life.
Coevolution
The word "coevolution" speaks to organisms or systems
that have interacted in ways that have influenced their evolution over time.
Examples include:
- Over millions of years of coevolution, the yucca moth has come
to depend exclusively on the yucca plant blossoms as a repository for eggs and
on the seeds as a food source for its larvae, and the yucca plant has come to
depend exclusively on the moth as an agent for pollination.
- Comparably, the minute fig wasp has come to depend solely
on the fig tree's tiny seed-bearing female flowers (located inside the fleshy
syconium, a hollow receptacle that also contains numerous fruitlets and pollen-bearing
male flowers) as repositories for eggs and on plant tissue for its larvae's food
source, and the fig tree has come to depend solely on the wasp as its agent for
pollination.
- In a competitive and ongoing coevolutionary relationship,
the common garter snake continually evolves new levels of immunity to the toxins
of one of its prey, the newt, while the newt continually evolves new toxins for
defense from the attacks of its predator. (Reported by S. L. Geffeney and associates
in Science Magazine, 2002.)
Mutualism
The word "mutualism" speaks to organisms or systems that have evolved
mutually beneficial or complementary relationships, which may be highly exclusive
or more generalized. The interdependent relationships between the yucca moth
and the yucca plant and the fig wasp and the fig tree typify exclusive mutualism.
Interdependent relationships between communities of organisms exemplify the more
general mutualism; these include, for instance:
Insects, hummingbirds and even bats may depend on various flower
species for food in the form of sugar-rich nectar or solid pollen, and the flower
species depends on its various animal partners for the service of pollination.
Birds may rely, seasonally, on plants' berries or fruits as sources of nourishment,
and the plants rely on the birds as distributors of (undigested) seeds.
Mushrooms,
growing in a forest, may envelop the roots of various tree species, stabilizing
the soil matrix and promoting the hosts' water absorption while the trees provide
mushrooms with essential sugars and starches.
Author: Jay Sharp
 Watch
a video about the Joshua Tree (Yucca brevifolia).
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