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Extensive variation in sperm morphology in a frog with no sperm competition

BACKGROUND: Recent comparative studies of several taxa have found that within-species variation in sperm size decreases with increasing levels of sperm competition, suggesting that male-male gamete competition selects for an optimal sperm phenotype. Previous studies of intraspecific sperm length var...

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Autores principales: Stewart, Kathryn A., Wang, Rachel, Montgomerie, Robert
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735968/
https://www.ncbi.nlm.nih.gov/pubmed/26832366
http://dx.doi.org/10.1186/s12862-016-0601-8
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author Stewart, Kathryn A.
Wang, Rachel
Montgomerie, Robert
author_facet Stewart, Kathryn A.
Wang, Rachel
Montgomerie, Robert
author_sort Stewart, Kathryn A.
collection PubMed
description BACKGROUND: Recent comparative studies of several taxa have found that within-species variation in sperm size decreases with increasing levels of sperm competition, suggesting that male-male gamete competition selects for an optimal sperm phenotype. Previous studies of intraspecific sperm length variation have all involved internal fertilizers where some other factors—e.g., sperm storage and sperm movement along the walls of the female’s reproductive tract—probably also influence and reduce sperm size variation. Thus external fertilizers, where those factors are absent, might be expected to exhibit even more variation when there is little or no sperm competition. To test that idea, we studied the sperm morphology of a North American chorus frog, the spring peeper (Pseudacris crucifer), a species in which males encounter little or no sperm competition. RESULTS: As expected, sperm size was highly variable in the spring peeper, largely due to variation in flagellum length within and among individual males, among populations and between mitochondrial lineages in southwestern Ontario. In addition, a large proportion of spermatozoa in all males was abnormal in such a way that the ability of abnormal spermatozoa to fertilize was probably compromised. There were no differences in the frequencies of abnormalities among populations or mitochondrial lineages. CONCLUSIONS: In the absence of sperm competition, we suggest that genetic drift has probably played a role in the generation of diversity in sperm morphology in this species, potentially resulting in the observed differences among populations. Such interpopulation difference in sperm morphology might be expected to increase the degree of reproductive isolation between populations even before other isolating mechanisms evolve. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12862-016-0601-8) contains supplementary material, which is available to authorized users.
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spelling pubmed-47359682016-02-03 Extensive variation in sperm morphology in a frog with no sperm competition Stewart, Kathryn A. Wang, Rachel Montgomerie, Robert BMC Evol Biol Research Article BACKGROUND: Recent comparative studies of several taxa have found that within-species variation in sperm size decreases with increasing levels of sperm competition, suggesting that male-male gamete competition selects for an optimal sperm phenotype. Previous studies of intraspecific sperm length variation have all involved internal fertilizers where some other factors—e.g., sperm storage and sperm movement along the walls of the female’s reproductive tract—probably also influence and reduce sperm size variation. Thus external fertilizers, where those factors are absent, might be expected to exhibit even more variation when there is little or no sperm competition. To test that idea, we studied the sperm morphology of a North American chorus frog, the spring peeper (Pseudacris crucifer), a species in which males encounter little or no sperm competition. RESULTS: As expected, sperm size was highly variable in the spring peeper, largely due to variation in flagellum length within and among individual males, among populations and between mitochondrial lineages in southwestern Ontario. In addition, a large proportion of spermatozoa in all males was abnormal in such a way that the ability of abnormal spermatozoa to fertilize was probably compromised. There were no differences in the frequencies of abnormalities among populations or mitochondrial lineages. CONCLUSIONS: In the absence of sperm competition, we suggest that genetic drift has probably played a role in the generation of diversity in sperm morphology in this species, potentially resulting in the observed differences among populations. Such interpopulation difference in sperm morphology might be expected to increase the degree of reproductive isolation between populations even before other isolating mechanisms evolve. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12862-016-0601-8) contains supplementary material, which is available to authorized users. BioMed Central 2016-02-01 /pmc/articles/PMC4735968/ /pubmed/26832366 http://dx.doi.org/10.1186/s12862-016-0601-8 Text en © Stewart et al. 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research Article
Stewart, Kathryn A.
Wang, Rachel
Montgomerie, Robert
Extensive variation in sperm morphology in a frog with no sperm competition
title Extensive variation in sperm morphology in a frog with no sperm competition
title_full Extensive variation in sperm morphology in a frog with no sperm competition
title_fullStr Extensive variation in sperm morphology in a frog with no sperm competition
title_full_unstemmed Extensive variation in sperm morphology in a frog with no sperm competition
title_short Extensive variation in sperm morphology in a frog with no sperm competition
title_sort extensive variation in sperm morphology in a frog with no sperm competition
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735968/
https://www.ncbi.nlm.nih.gov/pubmed/26832366
http://dx.doi.org/10.1186/s12862-016-0601-8
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