Danthonia Notes

Danthonia sericea:  In Flora North America volume 25, Danthonia epilis Scribn. [= D. sericea var. epilis (Scribn.) Gleason] is included in D. sericea without giving it any formal taxonomic recognition. Quinn and Fairbrothers (1971) are quoted as stating that "field differences in growth form do not persist under transplant garden and greenhouse conditions". Quinn has pointed out that the statement applied only to growth form, whether erect or weeping. He went on to state (in Email, 16 April 2003):

The pronounced differences in leaf-blade length and width and in lemma and sheath pubescence between NJ bog and upland populations persisted under all conditions. On page 535 of that paper, we pointed out that such habitat/ecological specificity suggested physiological differentiation of these morphological variants. Our subsequent research under controlled conditions documented that upland populations had thicker leaves, more pubescence, more pronounced adaxial surface ribbing, adaxial and abaxial stomata (bog populations had adaxial stomata only), more stomata on both the leaf blade and leaf sheath, and a greater percentage of pore space for the total leaf blade surface area (Bull. Torrey Bot. Club 105:45-49). We also documented that populations from wetter sites had significantly longer lemmas, and populations from the well-drained sites had a significantly greater number of spikelets per panicle, significantly heavier caryopses, and a greater percentage of florets with caryopses (Amer. J. Bot. 59:627-631).

In regards to differences in physiological responses, germination tests showed that seeds from wet habitats had significantly greater germination in light (alternating night-day) than in dark, while seeds from well-drained habitats had a higher germination percentage in dark than in light; and a comparison of germination responses obtained from six NJ populations in field plots on contrasting habitat types further revealed distinctive physiological adaptations for populations from differing habitats (Amer. J. Bot. 59:942-951). In photoperiod and flowering responses, populations with glabrous sheaths from bogs or wet areas in NJ required only adequate air and soil temperatures for growth and subsequent flowering, while populations from upland sites in NJ had an additional requirement for specific photoperiods (Ecology 53:227-234). In greenhouse and field transplant studies of responses to substrate moisture levels, greenhouse studies of responses of clonal and seed materials to saturated, moist, and dry moisture levels showed significant differences among populations in germination, growth, and survival.

Reciprocal transplants at upland and bog sites provided a 5-yr. field evaluation of the survival and performance of the morphological variants in each other's habitat under competitive conditions. Restriction to respective habitats was found to be primarily intolerance of wet site factors for the pubescent plants coupled with an inability of glabrous plants to successfully compete in upland sites (Amer. J. Bot. 62:884-891).

In a later Email (4 May 2003), he stated that:

...I am an ecologist, not a systematist, but as I reflect on the degree of ecological, morphological, and physiological differentiation of sericea and epilis, and recall that in 6 years of studying this complex that I seldom saw intermediate plants in areas where the two were adjacent, I believe that specific status is warranted for epilis.