COMMUNITY AND ECOSYSTEM ECOLOGY Evidence for Diet-Driven Habitat Partitioning of Melanoplinae and Gomphocerinae (Orthoptera: Acrididae) Along a Vegetation Gradient in a Western Oklahoma Grassland KENNETH MASLOSKI, 1,2 CARMEN GREENWOOD, 1 MICHAEL REISKIND, 3 AND MARK PAYTON 4 Environ. Entomol. 43(5): 1209Ð1214 (2014); DOI: http://dx.doi.org/10.1603/EN13349 ABSTRACT Grasshoppers (Orthoptera: Acrididae) are important arthropods in the grassland eco- system as sources of herbivory, nutrient recycling through frass production, and as prey items for other insects, mammals, and birds. It has been observed in previous research that common Acrididae subfamilies have dietary preferences: many species of Gomphocerinae are specialists on grass plants, many Melanoplinae species are polyphagous forb eaters. We characterized the community of Acri- didae along a vegetation gradient in the Beaver River Wildlife Management Area, Beaver County, OK, and tested the hypothesis that these subfamilies would be in greater abundance in areas dominated by their preferred food resource. Vegetation types were characterized into four different functional groups: grass, forb, litter, and bare ground. The proportion of cover of functional groups was found to be correlated with relative abundance of Gomphocerinae and Melanoplinae grasshoppers. Gom- phocerinae were in greater abundance in vegetation types consisting of a larger proportion of grass. Melanoplinae were in greater abundance in vegetation types consisting of larger proportions of forb cover. A factor analysis indicated that forb cover and grass cover contributed more than litter and bare ground cover to the relative abundance of these grasshopper subfamilies and it is our conclusion that this is evidence for dietary-based habitat partitioning as observed through subfamilial relative abun- dance. KEY WORDS Acrididae, feeding habit, habitat partitioning, factor analysis The distribution and diversity of animals across land- scapes are determined by abiotic and biotic factors. The availability of appropriate foods is one critical factor in determining where organisms are found, and therefore may structure entire communities (Huntz- inger et al. 2008). However, the availability of food is only one factor, and others (such as nesting and ovi- position sites) may be equally or more important (Be- lovsky et al. 1990, Bock et al. 1992, Russell and Detling 2003, Branson 2005). In this study, we use a vegetation gradient in a semiarid grassland in western Oklahoma to examine the importance of food availability and abiotic factors on the distribution of two subfamilies of grasshoppers (Orthoptera: Acrididae). It has been observed that there are unique dietary niches Þlled by different Acrididae subfamilies (Joern 1979, Behmer and Joern 2008). For example, Gom- phocerinae prefer to eat grasses and have relatively narrow dietary “niche breadths” or ranges of preferred food resources, whereas Melanoplinae prefer to eat herbaceous and woody forbs and are generally polyphagous, having a broader niche breadth (Joern 1979). These feeding habits may inßuence how grass- hoppers partition habitat use. In areas where the veg- etation composition is mostly grass, it may be expected that there will be a greater abundance and density of Gomphocerinae. Conversely, in areas that the vege- tation composition is mostly herbaceous and woody forbs, it may be expected that there will be a greater density and abundance of Melanoplinae (Joern 1979, Chapman 1990, Russell and Detling 2003, Behmer and Joern 2008). We tested the hypothesis that different plant func- tional group cover inßuences different grasshopper subfamily abundance along a vegetation gradient. We predicted that subfamilial composition of the grass- hopper community along a vegetation gradient would be correlated with functional composition of the plant community. SpeciÞcally, based on prior literature, we hypothesized that Gomphocerinae would be associ- ated with areas that had a greater percentage of grass, and that Melanoplinae would be associated with areas that had a greater percentage of forbs (Joern 1979, Chapman 1990, Russell and Detling 2003, Behmer and Joern 2008). We tested this hypothesis on the Beaver River Wildlife Management Area in Beaver County, OK. 1 Oklahoma State University Department of Entomology and Plant Pathology, 127 Noble Research Center, Stillwater, OK, 74078. 2 Corresponding author, e-mail: kenneth.masloski@okstate.edu. 3 North Carolina State University Department of Entomology, Campus Box 7613, 100 Derieux Place, Raleigh, NC, 27695. 4 Oklahoma State University Department of Statistics, 301 MSCS Building, Stillwater, OK, 74078. 0046-225X/14/1209Ð1214$04.00/0  2014 Entomological Society of America Downloaded from https://academic.oup.com/ee/article/43/5/1209/566626 by guest on 15 December 2022