Effect of plant-related threats on lizards of open sand steppes: a snapshot at the beginning of the spread of a novel invader

Grasslands have undergone significant loss of area and species diversity worldwide. The spread of invasive alien plant species further exacerbates the degradation of these ecosystems. Reptile populations are particularly affected by changes caused by invasive plants. Pannonian sand steppe grasslands, typical of the lowland regions within the Central European Carpathian Basin, are distinctive habitats that are rapidly shrinking in extent. These grasslands provide habitats for numerous grassland specialists, such as the Balkan wall lizard ( Podarcis tauricus ). Over the last few years, a new invader, the sand dropseed ( Sporobolus cryptandrus ), native to the North American prairies, has appeared in this community and spread aggressively. In addition, shrub encroachment due to pasture abandonment and reforestation has further reduced the area of these communities. In this study, we explored how the densities of two lizard species, the Balkan wall lizard and the Eastern green lizard ( Lacerta viridis ), a potential competitor of the Balkan wall lizard inhabiting these open grasslands, respond to increasing coverage of non-native invasive plants and the encroachment of woody vegetation. We surveyed lizard populations at six sites and assessed the effects of these threats using single-visit N -mixture models. The results showed varied effects on the abundance of the two lizard species: sand dropseed negatively affected the Balkan wall lizard, while woody encroachment positively influenced the Eastern green lizard.