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Hybridization of the Habitat
Vol. 2, No. 1 (Mar., 1948), pp. 1-9
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2405610
Page Count: 9
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1. Experimental evidence shows that sterility will not account for the rarity of hybrids under natural conditions. 2. Careful field analyses have shown that natural hybridization is largely limited to backcrosses which resemble the parental species so closely that special methods are required to detect them readily. 3. One of the factors limiting hybridization to such introgression is imposed by the habitat for the following reason: Two species differing in their habitat requirements will produce a first generation hybrid adjusted to a uniform intermediate environment. The second generation however consists of individuals each of which requires its own peculiar habitat for optimum development. Such heterogeneous habitats are seldom or never met with, the only approach to them being found in places where man has greatly altered natural conditions. 4. It is concluded that hybrid swarms can survive only in 'hybridized habitats.' While most of the latter result from human intervention, similar conditions have prevailed in pre-human times when new lands were opened up to colonization by diverse floras. At such times and places introgressive hybridization must have played an important role in evolution.
Evolution © 1948 Society for the Study of Evolution