Ecological significance of the genetic variation in Bouteloua curtipendula (Michx.)Torr.

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Title: Ecological significance of the genetic variation in Bouteloua curtipendula (Michx.)Torr.
Author: Andrea, Tomas de Pisani, Maria
Abstract: The two most common varieties of the grass Bouteloua curtipendula (Michx . )Torr . in North America use different strategies of clonal growth and have contrasting continental distributions . Variety caespitosa (phalanx form ) ranges from central Texas westward to Arizona and California and var . curtipendula (guerrilla form ) occurs in a more mesic region over the North American Great Plains . This study sought to determine whether the strategies had an ecological significance and investigated the possible relationship between changes in environmental factors and characteristics of each clonal growth strategy . Varieties showed to be morphologically variable , but the variability did not follow the pattern of the precipitational gradient . The abundance of var . curtipendula was related to soil depth and parent material (limestone types ) . Abundance of var . caespitosa could not be explained by any environmental factor separately . The performance of clones of the two growth forms in response to changes in resource availability (light and nutrients ) and defoliation suggested similarities between the varieties in photosynthetic rate and only showed differences in water potential under extreme conditions . The major differences were related to the proportion of biomass allocated to structures related with seed production versus propagation by rhizomes . Intra -variety genetic variation for several life history traits was detected even with a very small sample size . The caespitose growth form showed more biomass and rate of tiller recruitment after defoliation on average , but responses between genotypes were dissimilar . Varieties also showed levels of plasticity in the allocation to reproductive structures in response to environmental factors . Responses to fire were compared between varieties by experimental burnings with increasing load of artificial fuel . Plants of the two varieties reached similar maximum temperatures although var . caespitosa suffered temperatures considered to be lethal for longer periods of time . Results from this study suggested that , although characteristic of the pattern of clonal growth were not distinctly associated to resource availability or defoliation , distribution of the varieties may be related to a combination of biotic and abiotic factors beyond the factors studied here .
URI: http : / /hdl .handle .net /1969 .1 /1394
Date: 2005-02-17


Ecological significance of the genetic variation in Bouteloua curtipendula (Michx.)Torr.. Available electronically from http : / /hdl .handle .net /1969 .1 /1394 .

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