Multi-year monitoring of Asclepias syriaca spread in protected reserve of Deliblato Sand in Serbia

Abstract

Asclepias syriaca, (common milkweed), is an invasive species that has already been naturalized in 23 countries worldwide. Anticipated climate changes are predicted to help further its future spread beyond its current distribution. The common milkweed occurs in various habitats, most often those modified by humans, such as roadsides, railway areas, wastelands, abandoned orchards, vineyards, and abandoned arable land. Its massive occurrence threatens native species diversity, penetrating into natural and seminatural habitats. Deliblato Sands, special Serbian nature reserve, the largest European continental sandy terrain located in the south-east part of the Pannonia Plain, is also subject to invasion by A.syriaca. In 2015 we analyzed the presence of A.syriaca on borders of natural protected reserve along the roads leading to reserve, as well as on approx. 200 km of roads and paths in the natural reserve itselve. Those inner roads and paths were subsequently monitored in 2017, 2019, and 2021. for persistence and spread of already detected locations of A.syriaca and the occurrence of the new ones. Influence of proximity of reserve borders with different levels of infestation, type of use (commercial roads, tourist tracking paths), and levels of protection (three levels of protection exist on D. Sand), were analyzed. The largest increase in numbers was detected in the areas with the most intensive human activity. This study of dispersal and range extension can serve as a basis for further analysis of eco-evolutionary dynamics on A.syriaca populations and localities in the Deliblato Sand natural reserve.