Local and landscape-scale environmental filters drive the functional diversity and taxonomic composition of spiders across urban greenspaces

1. Urban patch colonization and species establishment within cities are
restricted by the behavioral, life history, and physiological attributes
of colonizing species, in conjunction with environmental filtering
processes at small and large spatial scales. To enhance local biodiversity
in urban greenspaces, these filtering processes need to be assessed so
that greenspace design and management can guide establishment of local
species pools. 2. We investigated the relative importance of local and
landscape-scale features on spider community assembly using a functional
and taxonomic approach. Within the shrinking city of Cleveland Ohio, we
established a field experiment wherein control vacant lots, urban meadows,
and low- & high-diversity pocket prairies were established across
eight neighborhoods (N = 32). Spiders were sampled in June-August of 2015
and 2016 using pitfall traps and vacuums. Spider functional diversity was
assessed using null models, while local and landscape drivers were
analyzed via canonical partial least squares and clustered image maps. 3.
Increased mowing strongly influenced spider communities leading to
lower-than-expected spider functional alpha and beta diversity in 2015.
Patch isolation and percentage impervious surface increased the functional
dissimilarity and taxonomic diversity of spiders in 2016, resulting in
higher-than-expected overall functional alpha diversity. We also found
that increasing plant height and biomass favored spiders with large
body-size and decreased the abundance of small web-weavers. 4. Synthesis
and applications. Our findings suggest that impervious surface is a strong
environmental filter that influences the colonization and establishment of
spider communities in cities. Additionally, while periodic mowing in
vacant lots benefits some spider taxa, it has a negative impact on the
establishment of several species, mainly larger spiders and those most
sensitive to disturbance. To conserve spiders and the biota depended upon
them, investment in managed greenspaces such as pocket prairies that
require infrequent mowing is warranted. In so doing, cities can enhance
urban biodiversity and beautify local neighborhoods.31-Mar-2020