| Popis: |
(in English) Sexual reproduction is considered a nearly universal feature of all eukaryotic organisms and has been hypothesized to be their ancestral state. Sexual reproduction is mainly represented by meiotic division, recombination, production of haploid gametes and fertilization. Although molecular and cytological mechanisms underlying meiosis are highly conservative they may be disrupted in numerous ways leading to the emergence of so-called asexual lineages. The proximate origins of asexuality may differ for particular taxa. In vertebrates, asexuality frequently is triggered by interspecific hybridization. Nowadays "classical" theories predict that asexuals should not be able to persist on a long-term evolutionary scale. However, the hybrid lineages have to overcome short-term disadvantages, such as postzygotic barriers ranging from complete hybrid sterility to altered meiosis resulting in asexual reproduction and even ploidy elevation. Despite that hybrid sterility is one of the most common outcomes of interspecific hybridization, however various lineages found their ways to alleviate these problems and produce viable clonal gametes. The knowledge about proximate mechanisms of unreduced gamete formation in asexual lineages is very limited as many studies were restricted due to methodological... |
