期刊
AMERICAN NATURALIST
卷 183, 期 5, 页码 671-681出版社
UNIV CHICAGO PRESS
DOI: 10.1086/675496
关键词
character displacement; population variation; hybrid speciation; Galapagos; Lorenzian imprinting; Darwin's finches
资金
- Natural Sciences and Engineering Research Council of Canada
- National Science Foundation
- McGill University
- Class of 1877 fund of Princeton University
This article explores how introgressive hybridization enhances the evolutionary effects of natural selection and how, reciprocally, natural selection can enhance the evolutionary effects of introgression. Both types of interaction were observed during a 40-year study of Darwin's finches (Geospiza) on the small Galapagos island of Daphne Major. Hybrids, produced rarely by Geospiza fortis (medium ground finch) breeding with Geospizascandens (cactus finch) and Geospizafuliginosa (small ground finch), survived and bred as well as the parental species in the past 3 decades. By backcrossing, they increased the standing genetic variation and thereby the evolutionary responsiveness of the populations to natural selection. Natural selection occurred in droughts and oscillated in direction as a result of climatically induced fluctuations in food composition. Introgressive hybridization has led to the formation of a new lineage. It was initiated by a large, introgressed, hybrid male with a unique song and genetic marker that immigrated from the nearby island of Santa Cruz and bred with local hybrids and with G. fortis. All members of the lineage died in the 2003-2005 drought except a brother and a sister, who then bred with each other. Subsequent increase in the lineage was facilitated by selective mortality of the largest G. fortis. Breeding endogamously, the lineage is behaving as a biological species.
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