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

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 effec...

Full description

Saved in:
Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2011-01, Vol.108 (2), p.674-679
Main Authors: Grant, Peter R., Grant, B. Rosemary
Format: Article
Language:English
Subjects:
Animal reproduction
Animals
Biological Evolution
Biological Sciences
Biological variation
Birds
Breeding
Cohort Studies
Ecological competition
Ecuador
Environment
Evolution
Evolutionary genetics
Female
Female animals
Finches
Genetic Variation
Genetics
Heterozygote
Longevity
Male
Male animals
Mating behavior
Predation
Regression Analysis
Sexual Behavior, Animal
Time Factors
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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).
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1018080108