Gastrophysa viridula (Coleoptera: Chrysomelidae) in the Czech Republic: Decline in a once abundant invasive oligophagous consumer of Rumex

Abstract

While the progress of the spread of invasive species of insects in new geographical areas are usually intensively monitored, the decline of these species often escape attention and is poorly documented. In this study, we record the decline in abundance of Gastrophysa viridula (DeGeer), an invasive oligophagous consumer of dock (Rumex spp.). This species originally inhabited Alpine regions. In the late 1800s, G. viridula was recorded in montane areas in the Czech Republic and then throughout this country. Gastrophysa viridula was very abundant in 1995–1999, when we found it in all of the 177 stands of R. obtusifolius inspected in western Czech Republic. In a repeated study of its occurrence in the same area from 2019–2020, this species was present in < 30% of 434 of the stands inspected and was only abundant (≥ 55% of plants in the stand infested by G. viridula) in < 4% of these stands. Thus the local occurrence and abundance of G. viridula had decreased signifi cantly. Of the possible reasons for this decline the most probable are the effect of climate warming on host plant seasonality, changes in agricultural use of grasslands and fragmentation of large stands of dock.