Gametogenesis of intergroup hybrids of hemiclonal frogs

Abstract

European water frog hybrids Rana esculenta (R. ridibundarR. lessonae) reproduce hemiclonally, by hybridogenesis : in the germ line they exclude the genome of one parental species and produce haploid gametes with an unrecombined genome of the other parental species. In the widespread L-E population system, both sexes of hybrids (E) coexist with R. lessonae (L). They exclude the lessonae genome and produce ridibunda gametes. In the R-E system, hybrid males coexist with R. ridibunda (R); they exclude either their ridibunda or their lessonae genome and produce sperm with a lessonae or with a ridibunda genome or a mixture of both kinds of sperm. We examined 13 male offspring, 12 of which were from crosses between L-E system and R-E system frogs. All were somatically hybrid. With one exception, they excluded the lessonae genome in the germ line and subsequently endoreduplicated the ridibunda genome. Spermatogonial metaphases contained a haploid or a diploid number of ridibunda chromosomes, identified through in situ hybridization to a satellite DNA marker, and by spermatocyte I metaphases containing a haploid number of ridibunda bivalents. The exception, an F1 hybrid between L-E system R. lessonae and R-E system R. ridibunda, was not hybridogenetic, showed no genome exclusion, and evidenced a disturbed gametogenesis resulting from the combination of two heterospecific genomes. None of the hybridogenetic hybrids showed any cell lines excluding the ridibunda genome, the pattern most frequent in hybrids of the R-E system, unique to that system, and essential for its persistence. A particular combination of R-E system lessonae and R-E system ridibunda genomes seems necessary to induce the R-E system type of hemiclonal gametogenesis. Gametogenesis of intergroup hybrids of hemiclonal frogs SummaryEuropean water frog hybrids Rana esculenta (R. ridibundarR. lessonae) reproduce hemiclonally, by hybridogenesis : in the germ line they exclude the genome of one parental species and produce haploid gametes with an unrecombined genome of the other parental species. In the widespread L-E population system, both sexes of hybrids (E) coexist with R. lessonae (L). They exclude the lessonae genome and produce ridibunda gametes. In the R-E system, hybrid males coexist with R. ridibunda (R) ; they exclude either their ridibunda or their lessonae genome and produce sperm with a lessonae or with a ridibunda genome or a mixture of both kinds of sperm. We examined 13 male offspring, 12 of which were from crosses between L-E system and R-E system frogs. All were somatically hybrid. With one exception, they excluded the lessonae genome in the germ line and subsequently endoreduplicated the ridibunda genome. Spermatogonial metaphases contained a haploid or a diploid number of ridibunda chromosomes, identified through in situ hybridization to a satellite DNA marker, and by spermatocyte I metaphases containing a haploid number of ridibunda bivalents. The exception, an F1 hybrid between L-E system R. lessonae and R-E system R. ridibunda, w...

Gamete production patterns and mating systems in water frogs of the hybridogenetic Pelophylax esculentus complex in north-eastern Ukraine

“…; Tunner and Heppich‐Tunner ; Ragghianti et al. ). We also found few, probably, recombinant diploid hybrids in the Seversky Donets River drainage.…”

Potential impact of genome exclusion by alien species in the hybridogenetic water frogs (Pelophylax esculentus complex)

“…This can be verified by means of experimental crosses. A first attempt of such crosses between water frogs of the L-E and R-E system has been made by Ragghianti et al (2007). They concluded that a particular combination of the R-E system lessonae genome and the R-E system ridibundus genome is necessary to induce a ridibundus genome elimination (Ragghianti et al 2007).…”

Multi-event models reveal the absence of interaction between an invasive frog and a native endangered amphibian

“…Furthermore, previous studies have shown that PR is a ubiquitous amphibian, breeding in a wide variety of flowing and stagnant waters such as rivers, brooks, dead arms, reservoirs and lakes (Pagano et al 2001;Van Buskirk 2003), as well as smaller bodies of water, such as ponds in gravel beds (Joly and Morand 1994;Morand and Joly 1995). As a consequence, this invasion has had an impact on closely related Ranid taxa, observed in the form of competition at the larval stage (Luquet et al 2011) and also in genetic introgression (Holsbeek and Jooris 2010;Hotz and Uzzell 1983;Hotz et al 1985;Plötner et al 2008;Ragghianti et al 2007). However, the consequences of this colonization on other amphibian native species have not been previously investigated.…”