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Impact of gamete production on breeding systems and population structure of hybridogenetic frogs of the Pelophylax esculentus complex: The evolutionary potential of interspecific hybridization


Pruvost, Nicolas B M. Impact of gamete production on breeding systems and population structure of hybridogenetic frogs of the Pelophylax esculentus complex: The evolutionary potential of interspecific hybridization. 2013, University of Zurich, Faculty of Science.

Abstract

The European water frog Pelophylax esculentus (genome LR) is a natural hybrid between P. lessonae (LL) and P. ridibundus (RR). It presents a peculiar quasi-sexual reproductive mode known as hybridogenesis: the hybrid excludes one of the parental species’ genomes at a pre-meiotic stage of gametogenesis, thus producing gametes containing clonal copies of the other parental genome. By mating with the parental species whose genome has been excluded it re-establishes hybridity at each generation. Moreover, because of its hybrid nature and resulting problems of chromosome pairing at gametogenesis, P. esculentus also produces diploid gametes from time to time. These gametes often lead to the generation of triploid frogs which will allow, under certain ecological conditions, the establishment of all hybrid populations which are maintained without the genetic contribution of either parental species. Over the past decade, such populations have been well studied in the north-western part of Europe, but the presence of triploid water frogs has also been reported for various areas in Central Europe. However, for those localities details on the breeding system, i.e. the genetic contribution of the various frog types, are usually lacking. The major goals of this thesis were to (a) investigate the Central European populations more closely, (b) to compare the breeding systems there with that in all-hybrid populations from Northern Europe and (c) find out whether triploid water frogs in different areas are of mono- or polyphyletic origin. In chapter one I used microsatellite DNA analyses and crossing experiments to compare five populations (one in Poland, two in Germany and two in Slovakia) presenting different population structures. Indices of 2 heterozygosity and of genetic differentiation allowed to depict the genetic interactions between the different type of frogs (LL, LLR, LR, LRR and RR). I was then able to define and differentiate the breeding systems occurring in each of them and to propose an evolutionary scenario for the appearance and maintenance of the all-hybrid populations. Chapter two presents a collaborative study with Alexandra Hoffmann. Here we enlarged our survey to populations distributed all over Europe and used microsatellite DNA and mitochondrial DNA (mtDNA) analyses to find patterns of genetic structure among different breeding system types. We found that genetic diversity among hybrid populations is influenced by geographic location (latitude, longitude) and by the proportions of parental genotypes in the hybrid population. Furthermore, we identified genetic clusters from both microsatellites and mtDNA, which indicate that there are at least two separate polyploid hybrid clades existing today: one in Northern and East- Central Europe and one in Eastern Europe (Eastern Ukraine).

Abstract

The European water frog Pelophylax esculentus (genome LR) is a natural hybrid between P. lessonae (LL) and P. ridibundus (RR). It presents a peculiar quasi-sexual reproductive mode known as hybridogenesis: the hybrid excludes one of the parental species’ genomes at a pre-meiotic stage of gametogenesis, thus producing gametes containing clonal copies of the other parental genome. By mating with the parental species whose genome has been excluded it re-establishes hybridity at each generation. Moreover, because of its hybrid nature and resulting problems of chromosome pairing at gametogenesis, P. esculentus also produces diploid gametes from time to time. These gametes often lead to the generation of triploid frogs which will allow, under certain ecological conditions, the establishment of all hybrid populations which are maintained without the genetic contribution of either parental species. Over the past decade, such populations have been well studied in the north-western part of Europe, but the presence of triploid water frogs has also been reported for various areas in Central Europe. However, for those localities details on the breeding system, i.e. the genetic contribution of the various frog types, are usually lacking. The major goals of this thesis were to (a) investigate the Central European populations more closely, (b) to compare the breeding systems there with that in all-hybrid populations from Northern Europe and (c) find out whether triploid water frogs in different areas are of mono- or polyphyletic origin. In chapter one I used microsatellite DNA analyses and crossing experiments to compare five populations (one in Poland, two in Germany and two in Slovakia) presenting different population structures. Indices of 2 heterozygosity and of genetic differentiation allowed to depict the genetic interactions between the different type of frogs (LL, LLR, LR, LRR and RR). I was then able to define and differentiate the breeding systems occurring in each of them and to propose an evolutionary scenario for the appearance and maintenance of the all-hybrid populations. Chapter two presents a collaborative study with Alexandra Hoffmann. Here we enlarged our survey to populations distributed all over Europe and used microsatellite DNA and mitochondrial DNA (mtDNA) analyses to find patterns of genetic structure among different breeding system types. We found that genetic diversity among hybrid populations is influenced by geographic location (latitude, longitude) and by the proportions of parental genotypes in the hybrid population. Furthermore, we identified genetic clusters from both microsatellites and mtDNA, which indicate that there are at least two separate polyploid hybrid clades existing today: one in Northern and East- Central Europe and one in Eastern Europe (Eastern Ukraine).

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Item Type:Dissertation (monographical)
Referees:Reyer Heinz-Ulrich, Vorburger Christoph
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
UZH Dissertations
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2013
Deposited On:12 Dec 2013 15:19
Last Modified:15 Apr 2021 14:26
OA Status:Green

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