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Masked Damage: Mutational Load in Hemiclonal Water Frogs


Vorburger, C; Schmeller, D S; Hotz, H; Guex, G D; Reyer, H U (2009). Masked Damage: Mutational Load in Hemiclonal Water Frogs. In: Schön, I; Martens, K; Van Dijk, P. Lost Sex: The Evolutionary Biology of Parthenogenesis. Chapter 20: Springer Science+Business Media, 433-446.

Abstract

Hemiclonal hybrids of Western Palearctic water frogs of the Rana esculenta complex transmit only one parental genome to their offspring without recombination (hybridogenesis). Such genomes are thus prone to accumulate deleterious mutations. The frog complex is unique among hybridogens in that hemiclonal hybrids occur in both sexes. This provides the opportunity of using experimental crosses to produce offspring possessing two clonal genomes of various origins and thereby study their homozygous and heterozygous effects on fitness. Here we review work that made use of this possibility to assess the evolutionary consequences of clonal inheritance in water frogs. Overall, these studies indicate that clonally transmitted genomes bear a substantial load of fixed deleterious mutations, yet these mutations appear to have minor effects on fitness in the heterozygous state. We also point out potential mechanisms for episodic recombination by which otherwise clonal genomes may be purged of deleterious alleles, and we present evidence for such episodic recombination to occur in natural populations of hybridogenetic frogs. Finally, we provide an outlook on work in progress that exploits the peculiarities of this system to obtain relevant estimates of the frequency of segregating lethal mutations in sexual populations of water frogs.

Hemiclonal hybrids of Western Palearctic water frogs of the Rana esculenta complex transmit only one parental genome to their offspring without recombination (hybridogenesis). Such genomes are thus prone to accumulate deleterious mutations. The frog complex is unique among hybridogens in that hemiclonal hybrids occur in both sexes. This provides the opportunity of using experimental crosses to produce offspring possessing two clonal genomes of various origins and thereby study their homozygous and heterozygous effects on fitness. Here we review work that made use of this possibility to assess the evolutionary consequences of clonal inheritance in water frogs. Overall, these studies indicate that clonally transmitted genomes bear a substantial load of fixed deleterious mutations, yet these mutations appear to have minor effects on fitness in the heterozygous state. We also point out potential mechanisms for episodic recombination by which otherwise clonal genomes may be purged of deleterious alleles, and we present evidence for such episodic recombination to occur in natural populations of hybridogenetic frogs. Finally, we provide an outlook on work in progress that exploits the peculiarities of this system to obtain relevant estimates of the frequency of segregating lethal mutations in sexual populations of water frogs.

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8 citations in Web of Science®
9 citations in Scopus®
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Additional indexing

Item Type:Book Section, not 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:2009
Deposited On:10 Nov 2009 07:40
Last Modified:05 Apr 2016 13:31
Publisher:Springer Science+Business Media
ISBN:978-90-481-2771-9 (P) 978-90-481-2770-2 (E)
Publisher DOI:10.1007/978-90-481-2770-2_20
Permanent URL: http://doi.org/10.5167/uzh-23697

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