Keystone species have large impacts on community and ecosystem properties, and create important ecological interactions with other species. Prairie dogs (Cynomys spp.) and banner-tailed kangaroo rats (Dipodomys spectabilis) are considered keystone species of grassland ecosystems, and create a mosaic of unique habitats on the landscape. These habitats are known to attract a number of animal species, but little is known about how they affect arthropod communities. Our research evaluated the keystone roles of prairie dogs and kangaroo rats on arthropods at the Sevilleta National Wildlife Refuge in central New Mexico, USA. We evaluated the impacts of these rodents on ground-dwelling arthropod and grasshopper communities in areas where prairie dogs and kangaroo rats co-occurred compared to areas where each rodent species occurred alone. Our results demonstrate that prairie dogs and kangaroo rats have keystone-level impacts on these arthropod communities. Their burrow systems provided important habitats for multiple trophic and taxonomic groups of arthropods, and increased overall arthropod abundance and species richness on the landscape. any arthropods also were attracted to the aboveground habitats around the mounds and across the landscapes where the rodents occurred. Detritivores, predators, ants, grasshoppers, and rare rodent burrow inhabitants showed the strongest responses to prairie dog and kangaroo rat activity. The impacts of prairie dogs and kangaroo rats were unique, and the habitats they created supported different assemblages of arthropods. Where both rodent species occurred together on the landscape, there was greater habitat heterogeneity and increased arthropod diversity.
Landscape-scale plots: We compared grasshoppers on plots occupied by:1) both species (Pdog+Krat plot);2) only kangaroo rats (Krat plot); and 3) both species, but where prairie dogs inhabited one half of the plot and kangaroo rats inhabited the other half (Transition plot).Sampling Design
The landscape-scale plots were 180 m x 180 m. Grasshoppers were visually sampled along strip transect lines established along each gridline of the landscape-scale plots, using a 5 x 5 grid array. Strip transects on the landscape-scale plots measured 1 m x 30 m.Field methods
Grasshoppers were sampled by walking slowly along each transect,tapping the soil and vegetation with a 1 m long, 1.27 cm diameter white PVC pipe. Grasshoppers flushed from the ground were counted and identified to species, and the substrate (i.e., plant species, bare soil) they were observed on was recorded. This is the standard method used at both the SEV and Jornada LTER sites, and is similar to that developed by Paftd (1982). Grasshoppers were sampled during spring (April) and fall (September), from fall 1999 through spring 2002 at the SNWR.Laboratory Procedures
Grasshopper voucher specimens from this study were deposited in the collection of the Arthropod Division, Museum of Southwestern Biology at the University of New Mexico.
01/09/2009 (YX): the metadata was entered from metadata supplied by Ana Davidson 1/25/2008
(Yang Xia) - updated and modified metadata to correct format;checked data for missing data points and errors;- any empty cells were filled in with either -999 for missing data
Additional Personnel with Data Collection
Julie McIntyre was part of the field crew in collecting/processing samples.
Additional Study Area Information
Study Area Name: Pino Gate
Study Area Location: The study site was located near the base of the Los Pinos mountains and directly adjacent to the nothern fencline of the SNWR at Pino Gate.Elevation: 1600 m
Vegetation: Burrograss (Scleropogon brevifolius), sand dropseed (Sporobolus cryptandrus), and black grama (Bouteloua eriopoda) were the dominant vegetation.
Soils: Deep clayey loam soilsGeology: On an upper bajada slope, in a broad swale
Climate: Long-term mean annual precipitation is 243 mm, about 60% of which occurs during the summer. Long-term mean monthly temperatures for January and July are 1.5°C and 25.1°C, respectively.
Site history: Historically, prairie dogs were common throughout the area, but were exterminated by the early 1970’s (John Ford, United States Department of Agriculture Wildlife Services, personal communication). Gunnison’s prairie dogs began to re-colonize the study site from adjacent private land in 1998. During our study, the colony occurred within a 5 ha area, near the base of the Los Piños Mountains in an area with deep clayey loam soils. The site has been long inhabited by kangaroo rats, and represents typical northern Chihuahuan Desert grasslandNorth Coordinate:34.406954South Coordinate:34.406954East Coordinate:106.606269West Coordinate:106.606269