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 been subject to a 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. Pannonic sand steppe grasslands are characteristic communities of Central Europe, but their extent is shrinking rapidly. These grasslands provide habitat 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, appeared in this community and spread aggressively. In addition, shrub encroachment due to pasture abandonment and reforestation further reduced the area of these communities. In this study, we explored how densities of two species of lizards, the Balkan wall lizard and the Eastern green lizard ( Lacerta viridis ), inhabiting these open grasslands respond to potential plant-related threats, such as the increasing coverage of non-native invasive plants and the encroachment of woody vegetation. We surveyed lizard populations at six sites and assessed the influence 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 affects the Balkan wall lizard, and woody encroachment positively influences the Eastern green lizard. There is a need for further research to refine the understanding of invasive plant impacts on native wildlife, and to develop effective management strategies to control the spread of invasive species like the Sand dropseed.