Are long-distance migrants constrained in their evolutionary response to environmental change?

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Are long-distance migrants constrained in their evolutionary response to environmental change?

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Pulido F; Widmer M Netherlands Institute of Ecology, PO BOX 40, ZG 6666 Heteren, The Netherlands. f.pulido@nioo.knaw.nl Long-distance migratory birds often show little phenotypic variation in the timing of life-history events like breeding, molt, or migration. It has been hypothesized that this could result from low levels of heritable variation. If this were true, the adaptability of long-distance migratory birds would be limited, which would explain the vulnerability of this group of birds to environmental changes. The amount of phenotypic, environmental, and genetic variation in the onset of autumn migratory activity was assessed in two garden warbler (Sylvia borin) populations differing in breeding phenology and the length of the breeding season with the aim of investigating the effects of selection on the adaptability of long-distance migrants. High heritabilities and additive genetic variance components for the timing of autumn migration were found in both populations. Although g