Whether the Presence of Di- and Triploid Hybrids, Pelophylax esculentus, Influences Gametogenesis of Their Parental Species, P. ridibundus

Abstract

Meiosis ensures efficient reproduction by the formation of viable gametes with a constant number of chromosomes. However, in natural hybrid complexes, where parental and hybrid lineages coexist, the fidelity of this process may be challenged. To better understand how this process functions in natural populations, we investigated, for the first time, the features of spermatogenesis and assessed the level of abnormal meiotic metaphases in the parental species Pelophylax ridibundus and P. lessonae of the hybridogenetic P. esculentus complex from 11 locations in Ukraine. Using Giemsa and/or Ag staining, we analysed 2,203 meiotic and 471 mitotic metaphases from 41 males. Most of the analysed spermatogonia and spermatocytes had chromosome numbers consistent with those forming viable gametes. The average level of aneuploidy in P. ridibundus males was 17% across all hemiclonal population systems analysed, which is significantly lower than in hybrids (p < 0.05). Furthermore, the lack of a significant difference (p = 0.93) in aneuploidy frequency among P. ridibundus from different population systems compared to the pure R-population suggests that the spermatogenesis of P. ridibundus is not affected by the presence of hybrids or the other parental species (P. lessonae). This cytogenetic robustness may contribute to the long-term stability of mixed populations, where P. ridibundus serves as a consistent source of haploid gametes necessary for the reproduction of P. esculentus hybrids.