Data from: Urbanization and plant invasion alter the structure of litter microarthropod communities

Anthropogenic activity underpins the creation of urban ecosystems, often
with introduced or invasive species playing a large role in structuring
ecological communities. While the effects of urbanization on charismatic
taxa such as birds, bees or butterflies have received much attention, the
impacts on small and inconspicuous organisms remain poorly understood.
Here, we assess how the community structure of leaf litter-inhabiting
microarthropods in city parks varies along an urbanization gradient in
Toronto, Canada. At each park, we established paired forest understory
plots which were either dominated by native vegetation or dog-strangling
vine (Vincetoxicum rossicum), an invasive species that is spreading
throughout northeastern North America and abundant in urban areas. We
compared microarthropod richness, abundance, and diversity in ecological
traits between invaded and non-invaded plots as well as compositional
dissimilarities among plots across the urbanization gradient. We recorded
123 genera and found: i) there was a negative effect of urbanization on
microarthropod richness and abundance but only in invaded plots; ii)
richness and abundance increased continuously with urbanization in
non-invaded plots, but peaked at intermediate urbanization levels in
invaded plots; and iii) there was significant turnover with increasing
urbanization, with distinct communities represented in highly urbanized
areas compared to less urbanized areas, regardless of whether invaded. We
also found litter microarthropod richness and abundance increased with
soil ammonium and decreased with nitrate. These trends were especially
strong for fungivorous microarthropods, however there was no relationship
between soil nutrients and urbanization or invasion. Urbanization and
biological invasion drive biodiversity change, and there is a need to
disentangle these effects on ecological communities and related ecosystem
processes. We show microarthropod communities change with urbanization,
with the effects of invasion most prominent in non-urban areas. Here,
there is high richness and abundance but low ecological trait diversity,
possibly because certain feeding traits are excluded and others
overrepresented. Understanding of urban ecological systems must include
knowledge of the microarthropods that interact widely across food webs,
form distinct communities in highly urban areas, and drive many of the
important ecological functions upon which people in cities depend.