Reproductive isolation is crucial for the process of speciation to progress. Sex chromosomes have been assigned a key role in driving reproductive isolation but empirical evidence from natural population processes has been restricted to organisms with degenerated sex chromosomes such as mammals and birds. Here we report restricted introgression at sex-linked compared to autosomal markers in a hybrid zone between two incipient species of European tree frog, Hyla arborea and H. orientalis, whose homologous X and Y sex chromosomes are undifferentiated. This large X-effect cannot result from the dominance or faster-X aspects of Haldane’s rule, which are specific to degenerated sex chromosomes, but rather supports a role for faster-heterogametic-sex or faster-male evolutionary processes. Our data suggest a prominent contribution of undifferentiated sex chromosomes to speciation.
Under incomplete reproductive isolation, secondary contact of diverged allopatric lineages may lead to the formation of hybrid zones that allow to study recombinants over several generations as excellent systems of genomic interactions resulting from the evolutionary forces acting on certain genes and phenotypes. Hybrid phenotypes may either exhibit intermediacy or, alternatively, transgressive traits, which exceed the extremes of their parents due to epistasis and segregation of complementary alleles. While transgressive morphotypes have been examined in fish, reptiles, birds, and mammals, studies in amphibians are rare. Here, we associate microsatellite‐based genotypes with morphometrics‐based morphotypes of two tree frog species of the Hyla arborea group, sampled across a hybrid zone in Poland, to understand whether the genetically differentiated parental species also differ in morphology between each other and their hybrids and whether secondary contact leads to the evolution of intermediate or transgressive morphotypes. Using univariate approaches, explorative multivariate methods (principal component analyses) as well as techniques with prior grouping (discriminant function analyses), we find that morphotypes of both parental species and hybrids differ from each other. Importantly, hybrid morphotypes are neither intermediate nor transgressive but found to be more similar to H. orientalis than to H. arborea.
The common wall lizard, Podarcis muralis, is a widely distributed European lizard which has been often introduced across the continent, including north of the continuous species range. Three such populations were recently discovered in the Strzelin Hills in Poland, but no information is available about their origin. We studied the morphological variation, demographic structure and ecology of these populations, as well as their possible origin based on cytochrome b mtDNA sequences. Between 2011 and 2019, the lizards were annually active from the first half of March to mid-October. Males attained significantly larger snout-vent length than females and had relatively larger heads. Almost half of all captured individuals exhibited at least one pileus scale anomaly. Analysis of colour polymorphism revealed the occurrence of three morphs: white, white-red and red. The oldest lizards reached the age of 8 years. These parameters of Polish populations do not deviate from those of other populations from similar latitudes. Molecular analysis revealed that they belong to the most common haplotype of Central European haplogroup I of the Central Balkan clade. This haplotype is widely distributed across the Czech Republic and Slovakia; however, genetic data do not allow determination of the exact origin of the Polish population. Human-mediated introduction from the closest localities, the Czech Republic or Slovakia, is probable but the relict status cannot at present be excluded.
Herpetofauna of opencast mines is poorly known and no comprehensive research has been previously carried out in this field. On the example of Lower Silesia this study aims to investigate this fauna. Observations, conducted in 22 different opencast mines in the eastern, lowland part of Lower Silesia (SW Poland), resulted in identification of a total of 19 species (14 amphibian species and 5 reptile species). No differences in the species composition, taking into account the exploited minerals, were found but the herpetofauna differ slightly after dividing the opencast mines into sandpits and quarries. Some species were recorded exclusively either in sandpits or in quarries. We also found statistically significant differences in the composition of herpetofauna and separately amphibian species as taking into account the status of exploitation of opencast mines. One species occurred primarily in exploited mines and four only in abandoned ones. No statistical differences between the number of species in exploited, recently abandoned and long since abandoned opencast mines.
Observations were conducted of 28 water bodies from 2006 to 2009 in Olawa, a mid-sized town (of about 31,000 residents) in southwestern Poland. 13 amphibian taxa were confirmed. These same taxa were also confirmed in the surrounding areas of the town. Twice as many amphibian species were found in areas affected to a lesser degree by urbanization than in heavily urbanized areas. Two groups of amphibians were distinguished, depending on their tolerance of urbanization at breeding ponds and sur roundings: 1) species preferring only natural terrain or areas close to being natural-Bombina bombina, Pelobates fuscus and Rana arvalis; 2) taxa breeding in both natural areas as well as those under the pres sure of urbanization-Tritunis cristatus, Tritunis vulgaris, Bufo bufo, Bufo viridis, Hyla arborea, Rana esculenta complex and Rana temporaria.
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