Tolerance range for dormancy loss and germination differs among dispersal strategies.

Abstract

Tolerance range for dormancy loss and germination differs among dispersal strategies

Ridma G. Bandara

Abstract

Germination has an optimum temperature and minimum and maximum thresholds [hereafter, tolerance range (TR)]. I reasoned that species with limited dispersal would be more specialized to local conditions and have narrower TR than those with wide dispersal. Four species contrasting in dispersal strategies were studied: Penstemon digitalis, P. tubaeflorus (gravity), Physalis longifolia (animal) and Asclepias syriaca (wind). I hypothesized that TR would differ (narrowest to widest): Penstemon < Physalis < Asclepias. Seeds were collected from MO to MN; stratified at 1, 5, and 9C; and incubated at 15/6, 20/10, 25/15, and 30/15C. Levins B was calculated; values approaching 1 vs. 0 represent a wide vs. narrow TR. Asclepias and Physalis seeds germinated highest at 20/10-30/15C regardless of stratification temperature, and Penstemon seeds at 15/6-30/15C following 1C stratification. TRs for cold-stratified seeds were: Penstemon < Physalis < Asclepias. Thus, my hypothesis was supported that TR varied according to dispersal strategy.