Causas de aptidão ao longo da vida dos tentilhões de Darwin em um ambiente flutuante

quinta-feira, janeiro 06, 2011

Causes of lifetime fitness of Darwin's finches in a fluctuating environment

Peter R. Grant1 and B. Rosemary Grant


Author Affiliations

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544

Contributed by Peter R. Grant, December 3, 2010 (sent for review November 15, 2010)


The genetic basis of variation in fitness of many organisms has been studied in the laboratory, but relatively little is known of fitness variation in natural environments or its causes. Lifetime fitness (recruitment) may be determined solely by producing many offspring, modified by stochastic effects on their subsequent survival up to the point of breeding, or by an additional contribution made by the high quality of the offspring owing to nonrandom mate choice. To investigate the determinants of lifetime fitness, we measured offspring production, longevity, and lifetime number of mates in four cohorts of two long-lived species of socially monogamous Darwin's finch species,Geospiza fortis and G. scandens, on the equatorial Galápagos Island of Daphne Major. Regression analysis showed that the lifetime production of fledglings was predicted by lifetime number of clutches and that recruitment was predicted by lifetime number of fledglings and longevity. There was little support for a hypothesis of selective mating by females. The offspring sired by extrapair mates were no more fit in terms of recruitment than were half-sibs sired by social mates. These findings provide insight into the evolution of life history strategies of tropical birds. Darwin's finches deviate from the standard tropical pattern of a slow pace of life by combining tropical (long lifespan) and temperate (large clutch size) characteristics. Our study of fitness shows why this is so in terms of selective pressures (fledgling production and adult longevity) and ecological opportunities (pulsed food supply and relatively low predation).

El Niño, extrapair offspring, heterozygosity, opportunistic breeding


1To whom correspondence should be addressed.

Author contributions: P.R.G. and B.R.G. designed research, performed research, analyzed data, and wrote the paper.

The authors declare no conflict of interest.

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