Obstinate nature: an ecology of individuals. Thoughts on reproductive behavior and biodiversity

Abstract

Marine turtles, salmon, and many other marine and terrestrial animals exhibit similar reproductive strategies in which the adults return to the site of their birth ("natal homing"). For these species, imprinting is the basic mechanism that allows every individual to place its progeny in an environment geographically similar to the one experienced at an early life stage. A tentative generalization of "natal homing" is presented within which homing is viewed as part of a continuum of reproductive strategies, all relying on imprinting. This generalization postulates that a newborn individual memorizes early environmental cues, which later determine the choice of its reproductive environment. Thus, the same mechanism accounts for successive generations reproducing at the same geographic location (philopatry) or aiming at a moving target, i.e., a set of environmental conditions that do not always have the same earth coordinates (dispersal). As a consequence, the adaptability of a population to its environment is ensured because of the diversity and multitude of imprinted individuals and not because of their individual adaptability. Diversity of life is thus perhaps more impressive than usually thought. Some ecological and evolutionary consequences of this generalization are explored and its application to marine fish discussed.