40 Years of Evolution: Darwin's Finches on Daphne Major Island
Language: English
Pages: 432
ISBN: 0691160465
Format: PDF / Kindle (mobi) / ePub
Renowned evolutionary biologists Peter and Rosemary Grant have produced landmark studies of the Galápagos finches first made famous by Charles Darwin. In How and Why Species Multiply, they offered a complete evolutionary history of Darwin's finches since their origin almost three million years ago. Now, in their richly illustrated new book, 40 Years of Evolution, the authors turn their attention to events taking place on a contemporary scale. By continuously tracking finch populations over a period of four decades, they uncover the causes and consequences of significant events leading to evolutionary changes in species.
The authors used a vast and unparalleled range of ecological, behavioral, and genetic data--including song recordings, DNA analyses, and feeding and breeding behavior--to measure changes in finch populations on the small island of Daphne Major in the Galápagos archipelago. They find that natural selection happens repeatedly, that finches hybridize and exchange genes rarely, and that they compete for scarce food in times of drought, with the remarkable result that the finch populations today differ significantly in average beak size and shape from those of forty years ago. The authors' most spectacular discovery is the initiation and establishment of a new lineage that now behaves as a new species, differing from others in size, song, and other characteristics. The authors emphasize the immeasurable value of continuous long-term studies of natural populations and of critical opportunities for detecting and understanding rare but significant events.
By following the fates of finches for several generations, 40 Years of Evolution offers unparalleled insights into ecological and evolutionary changes in natural environments.
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young exceeded mean longevities of their half sibs in less than half of the comparisons (45.6%, n = 68 pairs). Longevity is an indirect indication of their lifetime reproductive success (figs. 5.10 and 5.11). Third, individuals with extra-pair fathers did not produce more offspring than their half sibs: when matched with their half sibs they were usually less successful. This applies to number of eggs, where those with extra-pair fathers have the higher number in a minority of cases (37.5% of 16
individuals to groups or populations on a probabilistic basis. Asteroid — Extraterrestrial body. Impact of an asteroid on earth is believed to have contributed to the extinction of the dinosaurs. Autosomes — Chromosomes other than the sex chromosomes. Avipox — A disease of birds caused by a DNA virus (genus Avipoxvirus: Poxviridae) with pox symptoms. Backcross — Offspring produced by the breeding of an F1 hybrid with a member of one of the parental species. Designated by the symbol B, with
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numbers. G. scandens adults are less dependent than the juveniles upon seeds, and their diet is dominated by various products of Opuntia cactus at which they, and especially the males, are socially dominant to fortis. Character Displacement The third type of interspecific influence is evolutionary, causing a shift in phenotype in the next generation. Some phenotypes might be at a selective disadvantage compared with others in the same population when competing with another species. Phenotypes
record of sea-temperature fluctuations and associated rainfall (Dunbar et al. 1994). The record shows that it takes a long time for environmental variation to approach an asymptote (~170 years: Grant and Grant 1996c). Even though conditions were warmer in some half centuries than others, and more variable in some than others, there is no evidence of a long-term trend or of large-amplitude changes preventing a close approach to an asymptote (fig. 14.1). Box 14.1 Mollusks as Markers Fragments of