Gj. Vermeij, THE EVOLUTIONARY INTERACTION AMONG SPECIES - SELECTION, ESCALATION, AND COEVOLUTION, Annual review of ecology and systematics, 25, 1994, pp. 219-236
The hypothesis of escalation states that enemies-competitors, predator
s, and dangerous prey-are the most important agents of natural selecti
on among individual organisms, and that enemy-related adaptation and r
esponses brought about long-term evolutionary trends in the morphology
, behavior, and distribution of organisms over the course of the Phane
rozoic. In contrast to this top-down view of the role of organisms in
determining the directions of evolution, the hypothesis of coevolution
holds that two interacting species or groups of species change in res
ponse to each other. I review and evaluate these hypotheses in the lig
ht of criticisms about the existence of evolutionary trends and the ro
le of interactions of species in evolution. Models describing the evol
utionary effects organisms have on each other have been based largely
on population dynamics and on cost-benefit analyses of the net outcome
of interactions between species. Yet, the hypotheses of escalation an
d coevolution are statements about the nature, frequency, causes, and
role of selection. Although these models have provided valuable insigh
ts and have forced some modifications in the hypotheses of escalation
studies seeking to distinguish between escalation and coevolution will
require empirical observations and cost-benefit evaluations of the di
screte events of interaction that collectively constitute organism-cau
sed selection.