Competition among blue grama and buffalograss ecotypes: effects of soil and past neighbor interactions



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Texas Tech University


Native plants are adapted to their environment. Typically, the abiotic component of the environment is given the greatest attention in rangeland revegetation projects. Past research has suggested that selection of plants for fitness to their biotic environment may deserve increased attention. The hypothesis that biotic adaptation is an important component of increased fitness suggests that, for example, sympatric buffalograss should be better fit (have greater productivity and fecundity) to grow in blue grama neighborhoods (especially sympatric blue grama) than allopatric buffalograss populations. The objectives of this study were to: (1) explore the relationships among plant responses and the abiotic and biotic components of the environment, and (2) determine if blue grama or buffalograss have evolved genetically-based adaptations specific to their biotic, abiotic, or combined biotic and abiotic environment. Two populations of buffalograss and two of blue grama were studied; populations included allopatric individuals (e.g., buffalograss plants collected from areas without blue grama) and sympatric individuals (e.g., buffalograss plants collected from areas with blue grama). Ramets of the 4 populations were collected and transplanted into rephcates of 5 different neighborhoods. The neighborhoods included no neighbors, allopatric blue grama, sympatric blue grama, allopatric buffalograss, and sympatric buffalograss. The sites from which these populations were sampled were characterized in terms of soil and vegetation properties. Growth and fecundity responses of these populations were measured; soil water content and temperature patterns were described. Results show that sympatric and allopatric populations responded the same to each of the neighborhood treatments; there were no central population-neighbor population interactions. Likewise, there was no suggestion that populations were more adapted to their site of origin than to other sites. Intraspecific competition was often greater than interspecific competition, although usually they were similar. Site had a significant effect on growth and fecundity for both species. Buffalograss and blue grama respond to their environment, but there are apparently no adaptations in these populations that make them better fit to their site or neighborhood of origin.