Claim CB630:
Many pairs of species are mutually and completely dependent upon each
other. For example, fig trees require fig gall wasps to pollinate them,
and the wasps require the figs to live. Another such example, among many,
is the yucca and Pronuba yucca moth. If one species evolved first, it
could not have survived on its own; the mutualistic species must have come
into existence at essentially the same time.
Response:
- Obligate mutualism can evolve gradually from nonobligate associations.
For example, a yucca can be pollinated by many insects and gradually
specialize to attract just one moth, and a moth may live off many
species of yucca and gradually specialize on just one. In fact, some
yucca species are still pollinated by more than one moth, and the yucca
moth Tegeticula yuccasella pollinates several species of yucca
(Powell 1992).
References:
- Powell, Jerry A. 1992. Interrelationships of yuccas and yucca moths.
Trends in Ecology and Evolution 7(1): 10-15.
Further Reading:
Dawkins, Richard, 1996. Climbing Mount Improbable. New York:
W.W. Norton, chpts. 8 and 10.
Pellmyr, O., J. N. Thompson, J. M. Brown and R. G. Harrison, 1996.
Evolution of pollination and mutualism in the yucca moth lineage. The
American Naturalist 148(5): 827-847. (technical)
created 2004-1-16
