La niche écologique, mythe ou réalité ?

The niche concept in ecology can be approached either empirically or theoretically. The emphasis is laid in this paper on the empirical approach, and the authors make use of their personnal field experience to illustrate the points discussed. The usefullness of the Hutchinsonian concept of a multi-dimensonial niche is first emphasized, together with that of the distinction between the fundamental and the realized niche. Examples are given which will help to define and quantify a niche dimension in field conditions. Taking the spectrum of seed size eaten by four sympatric species of finches as an example, a number of concepts are discussed, such as the ecological profile of a species, the barycenter of its niche, niche breadth and niche overlap. Niche packing and the number of niches in a given ecological universe are then discussed, together with the concepts of alpha-, beta-and gamma-diversity. Niche regulation is also discussed at some length. The notion of a “ vacant niche” is shown to be a non-problem, and this is illustrated by some examples. It is pointed out that the mechanisms of niche regulation cannot be understood without reference to the concept of adaptive strategy, whether it be at the individual or demographic level. It is hard to understand how a species has developped its ecological niche without considering the nature of the selection pressures operating in more or less changing environments. To sum up, it is suggested that although it will always remain difficult (if not impossible) to identify and quantify all the n-dimensions of the niche of a given species, the concept remains most useful to stimulate working hypotheses, some of which at least can be tested in field conditions.Blondel Jacques, Bourlière François. La niche écologique, mythe ou réalité ?. In: La Terre et La Vie, Revue d'Histoire naturelle, tome 33, n°3, 1979. pp. 345-374