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No evidence for inbreeding avoidance in a natural population of song sparrows (Melospiza melodia)


Keller, L F; Arcese, P (1998). No evidence for inbreeding avoidance in a natural population of song sparrows (Melospiza melodia). American Naturalist, 152(3):380-392.

Abstract

We studied mate choice and inbreeding avoidance in a natural population of song sparrows (Melospiza melodia) on Mandarte Island, Canada. Inbreeding occurred regularly: 59% of all matings were between known relatives. We tested for inbreeding avoidance by comparing the observed levels of inbreeding to those expected if mate choice had been random with respect to relatedness. Independent of our assumptions about the availability of mates in the random mating model, we found that the expected and observed distributions of inbreeding coefficients were similar. as was the expected and observed frequency of close (f greater than or equal to 0.125) inbreeding. Furthermore, there was no difference in relatedness of observed pairs and those that would have resulted had birds mated instead with their nearest neighbors. The only evidence to suggest any inbreeding avoidance was a reduced rate of parent-offspring matings as compared to one random mating model but not the other. Hence, despite substantial inbreeding depression in this population, we found little evidence for inbreeding avoidance through mate choice. We present a simple model to suggest that variation in inbreeding avoidance behaviors in birds may arise from differences in survival rates: in species with low survival rates, the costs of forfeiting matings to avoid inbreeding may exceed the costs of inbreeding.

Abstract

We studied mate choice and inbreeding avoidance in a natural population of song sparrows (Melospiza melodia) on Mandarte Island, Canada. Inbreeding occurred regularly: 59% of all matings were between known relatives. We tested for inbreeding avoidance by comparing the observed levels of inbreeding to those expected if mate choice had been random with respect to relatedness. Independent of our assumptions about the availability of mates in the random mating model, we found that the expected and observed distributions of inbreeding coefficients were similar. as was the expected and observed frequency of close (f greater than or equal to 0.125) inbreeding. Furthermore, there was no difference in relatedness of observed pairs and those that would have resulted had birds mated instead with their nearest neighbors. The only evidence to suggest any inbreeding avoidance was a reduced rate of parent-offspring matings as compared to one random mating model but not the other. Hence, despite substantial inbreeding depression in this population, we found little evidence for inbreeding avoidance through mate choice. We present a simple model to suggest that variation in inbreeding avoidance behaviors in birds may arise from differences in survival rates: in species with low survival rates, the costs of forfeiting matings to avoid inbreeding may exceed the costs of inbreeding.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:September 1998
Deposited On:27 Apr 2012 07:20
Last Modified:07 Dec 2017 02:53
Publisher:University of Chicago Press
ISSN:0003-0147
Additional Information:Copyright 1998 by The University of Chicago
Publisher DOI:https://doi.org/10.1086/286176
Other Identification Number:ISI:000075387500005

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