Performance of Indigenous and Introduced Slender Wheatgrass in Alaska, and Presumed Evidence of Ecotypic Evolution
Leslie J. Klebesadel, Emeritus Professor of Agronomy
Agricultural and Forestry Experiment Station; Palmer, Alaska
Bulletin 85; September 1991 (20 pages)
Summary
Objectives of this study were to evaluate forage and seed production, winter hardiness, and stand longevity of several collections of native Alaskan slender wheatgrass (Agropyron trachycaulum (Link) Malte), and to compare their performance with introduced cultivars of slender wheatgrass and standard Alaska forage grasses in other species. Eight experiments at the Matanuska Research Farm (61.6° N. Lat.) near Palmer, Alaska demonstrated the superior winter hardiness and forage productivity of indigenous Alaskan slender wheatgrass lines (collected from 62° to 67° N. Lat.) over introduced cultivars 'Revenue' (originating at 52° to 53° N) from Saskatchewan and 'Primar' (adapted at 46° to 48° N) from the Pacific Northwest.
Forage yields of indigenous lines were lower in the seeding year with only basal leaves produced; seeding-year plants of local strain 'Alaska-44S' and introduced Revenue and Primar produced higher forage yields from numerous elongated culms per plant. In first-cut harvests in the second and later years, indigenous Alaskan lines produced heavy forage yields, but these were followed by generally much lower second-cutting yields, than introduced slender wheatgrass cultivars, 'Polar' or 'Manchar' bromegrass (Bromus inermis Leyss), or 'Engmo' timothy (Phleum pratense L.). Indigenous slender wheatgrass was more adversely affected by drought stress than were Alaska-44S, Revenue, or Primar. When not under drought stress, indigenous lines produced high seed yields.
The cumulative weight of evidence in these experiments strongly indicates that the Matanuska Valley roadside population of slender wheatgrass, included in these experiments as Alaska-44S, represents an early introduction (about 1930?) to Alaska from a more southern source, a population that has undergone evolutionary, selective modification toward adaptation to the subarctic environment. Alaska 44-S resembled cultivars introduced from more southern latitudes in: (a) producing elongated culms during the seeding year,
(b) retaining green (non-yellowing) foliage prior to freeze-up, (c) better foliar tolerance to severe moisture stress, and (d) high seed yield during moisture stress.
In contrast, it differed from introduced cultivars and was more similar to indigenous Alaskan slender wheatgrass in higher levels of autumn food-reserve storage and superior winter hardiness. These characteristics are important to survival and persistence in this area and indicative of adaptive change. The normally short life span of slender wheatgrass plants would tend to accelerate generational cycling, gene sorting, and rate of natural selection toward adaptation in a new environment.
These results confirm the desirability of using northern-adapted strains (cultivars, ecotypes) of perennial grasses for optimum winter survival in southcentral Alaska. The superior performance of the indigenous Alaskan slender wheatgrass collections underscores the desirability of further collections of native Alaskan ecotypes and species for evaluation for various uses in northern latitudes.