Differing impacts of two major plant invaders on urban plant-dwelling spiders (Araneae) during flowering season

Abstract

Plant invasions can have major impacts on ecosystems and influence global species diversity. In Central Europe, Himalayan balsam (Impatiens glandulifera) and American goldenrods (Solidago canadensis and S. gigantea) are important invaders often establishing dense and homogeneous stands, especially in urban and other disturbed habitats. We investigated their impacts on plant-dwelling spiders (abundance, family structure, guild structure) and potential spider prey items during flowering season within an urbanized landscape using a paired design comparing invaded and native reference vegetation plots. In general, flowering American goldenrods and Himalayan balsam had no significant impacts on the spider family composition. Invasion of American goldenrods further had no effect on total spider abundance and potential prey item abundance. In contrast, goldenrods showed a significantly increased crab spider (Thomisidae) abundance while being less inhabited by web builders. Himalayan balsam negatively influenced free hunters and running crab spider (Philodromidae) abundance, while we found no effects on other groups and total spider abundance. For Himalayan balsam, potential prey item abundance was higher than in native vegetation stands. Notwithstanding that our results only represent a snapshot of the system, they suggest that large-scale removal of urban goldenrod stands during flowering season might negatively influence local spider abundance, especially of crab spiders. Management efforts should therefore be accompanied by compensation measures to avoid disruptive effects on local plant-dwelling spider communities.

Can trait matching inform the design of pollinator‐friendly urban green spaces? A review and synthesis of the literature

“…At the local scale, conservation value of green spaces may be determined by local floral resource quality, quantity, and attractiveness to diverse pollinator groups. Other local factors such as soil and water availability, as well as the management practices of green spaces, may influence the availability and quality of resources for pollinators (Bauer et al, 2021; Erickson et al, 2022). At the landscape scale, the surrounding proportion of impervious surface in relation to other green spaces or conservation spaces, degree of urban warming, and level of urban pollution are important factors influencing the conservation value of urban green spaces (Biella et al, 2022; Birdshire et al, 2020).…”

Study isssues of invasive species of the genus Solidago

“…When studying thickets of invasive goldenrod species in ruderal urban areas in Germany (Karlsruhe), an increase in the number of crab spiders (Thomisidae) has been noted, but these floristic changes did not affect the total abundance and taxonomic composition of Araneae (Bauer et al, 2021).…”

The impact of restoration methods for Solidago-invaded land on soil invertebrates

“…Plant invasions have serious negative effects on ecosystems and species diversity 1 , 2 and can disrupt the linkages between the above- and belowground communities 3 , 4 . Goldenrods ( Solidago canadensis L. and Solidago gigantea Aiton.)…”