Genetic differentiation and admixture among Festuca idahoensis, F. roemeri, and F. ovina detected in AFLP, ITS, and chloroplast DNA

North American forms of the Festuca ovina L. complex, Festuca idahoensis Elmer and Festuca roemeri (Pavlick) E.B. Alexeev, are distributed broadly east and narrowly west of the Cascade Mountains, respectively. The psbA-trnH and rps16-trnK chloroplast DNA intergenic sequences, 18S-5.8S-26S nuclear ribosomal DNA internal transcribed spacer (ITS) sequences, and six AFLP primer combinations were used to investigate genetic relatedness and differences among 327 plant samples from 24 F. idahoensis and 33 F. roemeri natural-source germplasm accessions, two multiple-origin F. idahoensis × F. roemeri cultivars, one apparently admixed F. ovina × F. idahoensis accession, four naturalized populations or cultivars of Eurasian-source F. ovina s. l., and several Festuca arizonica Vasey, Festuca occidentalis Hooker, and Festuca rubra L. reference accessions. The AFLP profiles of individual plants were unique, but distance-based and Bayesian model-based clustering separated AFLP genotypes into groups corresponding to taxa. Approximately 15.9% of the AFLP variation was apportioned between F. idahoensis and F. roemeri, with the remaining 61.2% and 22.9% variation maintained within and among natural-source accessions, respectively. Genetic admixture between F. idahoensis, F. roemeri, and F. ovina was detectable and DNA sequence divergence was very low in the chloroplast and ITS regions. These three taxa are genetically differentiated, but capable of hybridization.

An assessment of variation in Idaho fescue [Festuca idahoensis (Elmer)] in southern Alberta

Idaho fescue (Festuca idahoensis Elmer) is a native grass species that has attracted interest for use in revegetation, reclamation and other applications. However, there is a serious shortage of commercially available seed and concern that germplasm used will not be adapted to the site. A component of adaptation is genetic variability that allows a species to occupy a greater range of environments. Field trials were conducted in southern Alberta to determine the genetic variability of phenotypic and performance characteristics among genotypes of Idaho fescue. Since grazing pressure may contribute to genetic selection and may therefore affect the variability within a population, we also compared genotypes taken from a heavily grazed paddock with those taken from a lightly grazed paddock. Forty-nine genotypes from three populations were randomly sampled in 1992, propagated vegetatively to produce plants for replicated trials and planted in four locations in 1993. Nine plant characteristics were observed from 1993 to 1997. Since the genotypes were grown in common environments, variation among them was assumed to be caused by genetic differences. All variables were affected (P < 0.05) by population, test location and year, while the effect of population was also influenced by test location and year for a few variables. While the Idaho fescue plants expressed differences (P < 0.05) among populations for all selected traits, they displayed considerable overlap in the range of values for all variables both within and among test locations. Therefore, while the populations may be different, individuals within populations exhibit common attributes over a large range. This suggests that sufficient genetic variability exists in all populations to allow successful establishment over a large range of environmental variability. Results from a secondary test suggest that selection pressure, induced by grazing, resulted in genotypes that were smaller in crown circumference, had less spring vigor, had shorter flowering tillers and produced less seed. However, this observation needs further validation with a more robust test. Key words: Morphology, genotypes, seed yield, winter kill, grazing response

Carbon allocation in Euphorbia esula and neighbours after defoliation

Weeds increase their dominance in a grazed plant community by avoiding herbivory and (or) by tolerating herbivory more than neighbouring plants. After defoliation, allocating carbon to shoots at the expense of roots may confer tolerance. We determined carbon allocation patterns of undefoliated and recently defoliated (75% clipping level) plants of the invasive leafy spurge (Euphorbia esula L.) growing with alfalfa (Medicago sativa L.), Kentucky bluegrass (Poa pratensis L.), or Idaho fescue (Festuca idahoensis Elmer). Plants were labeled with 13CO2 24 h after clipping to determine allocation patterns; all plants had equal access to the 13CO2. Based on relative distribution of 13C, defoliation did not affect the amount of carbon allocated to roots of E. esula. The amount of carbon allocated to shoots of E. esula was higher when growing with P. pratensis than when growing with the other species. Based on relative enrichment of 13C, defoliation increased sink strength of remaining shoots on defoliated E. esula plants. Conversely, roots of unclipped E. esula plants were stronger sinks for carbon than roots of clipped plants. Even though defoliation increased "sink strength" of remaining shoots of E. esula, the amount of carbon allocated to the root system was unaffected by defoliation, suggesting that uninterrupted allocation of carbon to its extensive root system, not increased allocation to its shoot system, confers grazing tolerance.

Length and Timing of Grazing on Postburn Productivity of Two Bunchgrasses in an Idaho Experimental Range

Plant mortality and productivity in semiarid grasslands may be affected by the length of time grazing is excluded during the postfire regeneration period. The degree of grazing tolerance for the semiarid bunchgrass species, Festuca idahoensis and Agropyron spicatum, exposed to fire, and how the variation in grazing tolerance was affected by the length of time allowed for undisturbed plant regeneration after fire, were central questions addressed in this study. We examined the degree of plant mortality and productivity that resulted from the interaction of fire and grazing. Plants exposed to fire alone, i.e., without subsequent defoliation, exhibited low plant mortality, although culm production was reduced relative to unburned plants. An early-season-defoliation treatment after fire resulted in the plant mortality as high as 50% for Festuca and 70% for Agropyron bunchgrasses. Plant height and the number of vegetative and reproductive culms were also most affected by this defoliation treatment. These detrimental effects were lessened when defoliation was delayed by one growing season after the fire. Although our results suggest that one growing season seems to be enough for both species to recover after the fire, more studies will be necessary to confirm these trends, and induce changes in current grazing management policies.

Biodiversity among Festuca (Poaceae) in North America: diagnostic evidence from DELTA and clustering programs, and an INTKEY package for interactive, illustrated identification and information retrieval

Biodiversity among taxa of Festuca occurring in North America has been investigated from a revised and illustrated database developed using the DELTA software package. The database includes common names; the place of valid publication of the name; the location of type specimens, when known, and whether we have examined them; synonymy; data on morphology, anatomy, and chromosome number(s); habitat and distribution information; subgeneric classification; taxonomic notes; and more than 200 images. The data are available on the Internet via the World Wide Web (WWW) at http://www.keil.ukans.edu/delta/or by anonymous file transfer protocol (ftp) from ftp.keil.ukans.edu, as natural-language descriptions and as an INTKEY interactive identification and information-retrieval package for MS-Windows. INTKEY and other DELTA programs have been used to assess biodiversity and have supported recognition of several species that have often been placed into synonymy (e.g., Festuca calligera and Festuca earlei), a status change for Festuca idahoensis subsp. roemeri comb.nov., placing Festuca brachyphylla subsp. breviculmis into synonymy with F. brachyphylla subsp. coloradensis, and suggested a taxonomy that is presented in an annotated list. Phenetic and cladistic analyses suggest that the traditional generic limits of Festuca and Lolium should be retained and four subgenera recognized within Festuca, subgg. Festuca, Leucopoa, Schedonorus, and Subulatae, with sects. Subulatae and Obtusae. Key words: DELTA, Festuca, Lolium, Poaceae, biodiversity, WWW, taxonomy.

The Relative Sensitivity of Two Bunchgrass Species to Fire

The response of two bunchgrass species, Festuca idahoensis and Agropyron spicatum, to fire was examined under three levels of fire severity. The fire treatment was applied with an instrument system that allowed precise control over the intensity and duration of fire, and full documentation of the temperatures experienced in various regions of each plant during the fire and postfire cooling phases. A quantitative index of fire exposure, or severity, for each plant was obtained by integrating the temperature curve for the meristematic crown region over the fire and postfire cooling periods. No significant plant mortality was observed at any fire severity level. Although tissue damage in newly initiated culms was observed for Festuca, this did not significantly affect culm or biomass productivity. Culm production was initiated earlier and more rapidly in Festuca than Agropyron, and within 60 days after fire exposure the total number of culms produced in Festuca was nearly that of unburned plants. Above ground biomass for both species was significantly less than that of unburned plants at the end of this 60-day period. Agropyron exhibited significantly less culm and biomass production at a moderate fire severity, whereas high fire severity was required for this reduction in Festuca. Contrary to previous studies, Festuca thus appears less sensitive to fire injury than Agropyron.