. Animal Ecology. Animal ecology. ENVIRONMENTAL NICHES FIG. 18-1 Species I finds optimal conditions in niche C, and reaches greatest abundance in that niche. It is also able to utilize niches B and D, but with less efficiency, and niches A and E only very poorly. Species 2 cannot utilize niches A, B, and C at all, finds D only partially suitable, but E and especially F very favorable. Species I and 2 overlap in niche D, but species 2 prevents any occupancy of niche E by species I. The absence of competition in niche A makes it open to a species evolving adaptations to it (from Mayr 1949). 4. W
. Animal Ecology. Animal ecology. ENVIRONMENTAL NICHES FIG. 18-1 Species I finds optimal conditions in niche C, and reaches greatest abundance in that niche. It is also able to utilize niches B and D, but with less efficiency, and niches A and E only very poorly. Species 2 cannot utilize niches A, B, and C at all, finds D only partially suitable, but E and especially F very favorable. Species I and 2 overlap in niche D, but species 2 prevents any occupancy of niche E by species I. The absence of competition in niche A makes it open to a species evolving adaptations to it (from Mayr 1949). 4. When competition occurs, it is severest be- tween organisms with the most similar require- ments. 5. In general, the closer the taxonomic relation- ship between them, the more similarity there is in needs and habits of species. 6. When new forms appear in a given locality, either by evolvement there or by invasion after evolutionary divergence elsewhere, they will either eliminate or be eliminated by their near- est relatives if they compete with them, unless 7. Each form becomes adapted to a different niche, in which case competition between them will cease, and they may occur in proximity. Evidence that interspecific competition is the most critical factor confining a species to this or that niche is available with the expansion of the species beyond the usual limits of its niche when this competition is removed. This expansion is often evident in geo- graphic differences in the niche characteristics of a species. In Scotland, the mountain hare occurs at high elevations, the common hare at lower ones. In Ireland, which was isolated as an island before the common hare could reach it, the mountain hare oc- curs at both high and low elevations and is differ- entiated into distinct subspecies (Huxley 1943). In the Canary Islands, the chaffinch Fringilla teydea breeds only in pine forests. The closely related F. coelcbs usually breeds in broad-leaved forests above and below the pin
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
