Positive Interactions between Desert Granivores: Localized Facilitation of Harvester Ants by Kangaroo Rats

Facilitation, when one species enhances the environment or performance of another species, can be highly localized in space. While facilitation in plant communities has been intensely studied, the role of facilitation in shaping animal communities is less well understood. In the Chihuahuan Desert, both kangaroo rats and harvester ants depend on the abundant seeds of annual plants. Kangaroo rats, however, are hypothesized to facilitate harvester ants through soil disturbance and selective seed predation rather than competing with them. I used a spatially explicit approach to examine whether a positive or negative interaction exists between banner-tailed kangaroo rat (Dipodomys spectabilis) mounds and rough harvester ant (Pogonomyrmex rugosus) colonies. The presence of a scale-dependent interaction between mounds and colonies was tested by comparing fitted spatial point process models with and without interspecific effects. Also, the effect of proximity to a mound on colony mortality and spatial patterns of surviving colonies was examined. The spatial pattern of kangaroo rat mounds and harvester ant colonies was consistent with a positive interspecific interaction at small scales (<10 m). Mortality risk of vulnerable, recently founded harvester ant colonies was lower when located close to a kangaroo rat mound and proximity to a mound partly predicted the spatial pattern of surviving colonies. My findings support localized facilitation of harvester ants by kangaroo rats, likely mediated through ecosystem engineering and foraging effects on plant cover and composition. The scale-dependent effect of kangaroo rats on abiotic and biotic factors appears to result in greater founding and survivorship of young colonies near mounds. These results suggest that soil disturbance and foraging by rodents can have subtle impacts on the distribution and demography of other species

Customer Relationship Management and Firm Performance: The Mediating Role of Business Strategy

As managers and academics increasingly raise issues about the real value of CRM, the authors question its direct and unconditional performance effect. The study advances research on CRM by investigating the role of critical mechanisms underlying the CRM-performance link. Drawing from the sources → positions → performance framework, the authors build a research model in which two strategic postures of firms – differentiation and cost leadership – mediate the effect of CRM on firm performance. This investigation also contributes to the literature by drawing attention to the differential impact of CRM in diverse industry environments. The study analyzes data from in-depth field interviews and a large-scale, cross-industry survey, and results reveal that CRM does not affect firm performance directly. Rather, the CRM-performance link is fully mediated by differentiation and cost leadership. In addition, CRM’s impact on differentiation is greater when industry commoditization is high. Full text PDF available online