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Reproductive isolation barriers maintain the integrity of species by preventing interspecific gene flow. They involve temporal, habitat or behavioral isolation acting before fertilization, and postzygotic isolation manifested as hybrid mortality or sterility. One of the approaches of how to study reproductive isolation barriers is through the analysis of hybrid zones. In this paper, we describe the structure of a hybrid zone between two crested newt species (Triturus cristatus and T. carnifex) in the southern part of the Czech Republic using morphological, microsatellite, and mitochondrial (mtDNA) markers. Specifically, we tested the hypothesis that the structure of the hybrid zone is maintained by species‐specific habitat preferences. Comparing the genetic structure of populations with geographical and ecological parameters, we found that the hybrid zone was structured primarily geographically, with T. cristatus‐like populations occurring in the northeast and T. carnifex‐like populations in the southwest. Despite T. cristatus tending to occur in deeper ponds and T. carnifex on localities with more shading, the effect of both ecological parameters on the structure of the zone was minimal. Next, we corroborated that T. carnifex individuals and some hybrids possess mtDNA of T. dobrogicus, whose nuclear background was not detected in the studied hybrid zone. Hybridization between T. carnifex and T. dobrogicus (resulting in unidirectional mtDNA introgression) had to predate subsequent formation of the hybrid zone between T. cristatus and T. carnifex. Populations of crested newts in the southern part of the Czech Republic thus represent a genetic mosaic of nuclear and mitochondrial genomes of three species. [ABSTRACT FROM AUTHOR]

Contributions of methane benthic fluxes and methane emissions to the total methane amount were studied during the summer season for two consecutive years. Considering the fact that methane is produced in great amount within hyporheic sediments, we have expected that both methane released by the benthic fluxes into the overlying water and methane emitted to the atmosphere should significantly affect the total methane budget of the stream water within the experimental area. In order to asses this assumption, we measured methane concentrations within the vertical sediment profile of a hyporheic zone, direct benthic methane fluxes by static chambers, methane concentrations in the surface water, and methane emissions into the atmosphere simultaneously. The methane concentrations in interstitial water tended sharply to increase with sediment depth (0.54-734.99 μmol L−1) and were strongly correlated with benthic fluxes ( r = 0.88, p < 0.05). We also found a considerable variability in the benthic methane fluxes (0-12.59 mmol m−2 day−1) and the spatial variability (0-71.43%) of the experimental area, suggesting that there may be various factors that affect the rate of benthic fluxes including methanotrophy in the top sediment layers. Generally, the contribution of benthic fluxes and methane emissions to the methane budgets of the experimental area was negligible (0.034 (0.45%) and 0.074 mol day−1 (0.98%), respectively). [ABSTRACT FROM AUTHOR]