Discordant response of spider communities to forests disturbed by deer herbivory and changes in prey availability

Abstract

Citation: Landsman, A. P., and J. L. Bowman. 2017. Discordant response of spider communities to forests disturbed by deer herbivory and changes in prey availability. Ecosphere 8(2):e01703. 10.1002/ecs2.1703Abstract. Despite the breadth of research on impacts of dense ungulate populations and invasive plants on native vegetation, work involving indirect effects on spider communities is explicitly lacking. Forest spiders depend on palatable insect prey and habitat structure, both of which are affected by herbivory and invasive vegetation. To examine the indirect interactions between spiders and these influential factors, we sampled spider communities, insect prey, and vegetation in paired deer exclusion plots in central Maryland. Spider abundance and richness increased with greater prey density, while increased habitat structure from deer exclusion reduced species richness and the abundance of a dominant web-building species. Multivariate analyses of spider families also demonstrated the importance of both prey availability and structural complexity to spider community composition. This work identifies the importance of both habitat structure and insect prey in defining the composition, abundance, and richness of forest spider communities. A long history of heavy browsing pressure has resulted in local spider fauna consisting of many species that are able to thrive in low-growing vegetation and open forest understories. Such changes to vegetative structure from dense deer populations and invasive plants have the potential to affect these important primary predators as well as araneophagic birds and the nutritional dynamics of forest food webs.

Invasive grass (Microstegium vimineum) indirectly benefits spider community by subsidizing available prey

“…For example, many of the dipteran species we collected belonged to taxa from detrital food webs, such as many within the Mycetophilidae. These results are similar to past research on the benefit of invasive plant species specifically to detrital communities (McCary et al., 2016) and the importance of plant structure to spider communities (Landsman & Bowman, 2017; Miyashita, Takada, & Shimazaki, 2004; Takada, Baba, Yanagi, Terada, & Miyashita, 2008).…”

“…These Our findings may be restricted to those areas with high ungulate densities and resulting depauperate understory vegetation: Deer densities in our sampling area were between 46 and 66 deer/km 2 while densities at much lower levels can cause significant impacts to understory forest vegetation and structure (Horsley, Stout, & de Calesta, 2003;Tilghman, 1989). Vegetation structure is a critical factor affecting the ability of a habitat to support understory spiders in forests with extensive ungulate herbivory (Landsman & Bowman, 2017;Miyashita et al, 2004;Takada et al, 2008). In habitats where additional native or non-native structure exists, the relationship between M. vimineum and the invertebrate community could reverse, as was noticeable in the Antietam plot pair and evident in the significance of the interaction term between Park and plant invasion on many of the response variables.…”

“…While we noted this in the present study with M. vimineum , similar trends may also arise with other invasive or native plants in areas with limited understory vegetation, given the additional structural complexity brought about by the plant. Vegetation structure is a critical factor affecting the ability of a habitat to support understory spiders in forests with extensive ungulate herbivory (Landsman & Bowman, 2017; Miyashita et al., 2004; Takada et al., 2008). In habitats where additional native or non‐native structure exists, the relationship between M. vimineum and the invertebrate community could reverse, as was noticeable in the Antietam plot pair and evident in the significance of the interaction term between Park and plant invasion on many of the response variables.…”

Diversity and Community Structure of Arthropods on Rice Ecosystem

“…and some other insect pest species (Betz & Tscharntke, 2017). Spider diversity is significantly dependent on vegetation structure (Landsman & Bowman, 2017). The species richness and abundance of spiders are higher in the abandoned fields in which more plant species grown than in rice fields (Baba, Tanaka, & Kusumoto, 2019).…”

Plant Mediated Interactions: Lower Sawfly Survival on Pines Previously Browsed by Moose

“…Research has shown that intense grazing of forest understory vegetation will lead to decreased understory height as well as changes in understory composition in boreal forest (Speed et al, 2014;Lorentzen Kolstad et al, 2018). Other studies investigating the subsequent effects of browsing on arthropod communities observed a change in both diversity and composition (Suominen et al, 1999;Landsman and Bowman, 2017;Lilleeng et al, 2018). One consequence of an altered predator community is subsequent effects on predation rates of insect herbivores, and plant damage levels.…”