Bandara, Ridma , Finch, Jessamine , Walck, Jeffrey , Hidayati, Siti , Havens, Kayri .
Tolerance range for dormancy loss and germination differs among dispersal strategies.
Seed dormancy loss and germination have an optimum temperature condition and minimum and maximum thresholds (hereafter, tolerance range). Tolerance ranges are important since they determine, in part, how species will respond to climate change. If a tolerance range includes future temperatures, then a species may persist in a habitat with a changing climate. On the other hand, if the range does not include future temperatures then the species must adapt or migrate or risk extinction. Tolerance ranges vary among species, but attributes influencing tolerance ranges are poorly understood. We postulated that dispersal strategy might play a role in determining tolerance ranges. Our reasoning was that species with limited dispersal would be expected to be more specialized to local environmental conditions and have narrower tolerance ranges compared to species with wide dispersal. We selected three eastern North American genera contrasting in dispersal strategies: Penstemon digitalis (gravity), Physalis longifolia ssp. subglabrata (animal) and Asclepias syriaca (wind). We hypothesized that temperature tolerance ranges for dormancy loss and germination would differ among these species in the following sequence (narrowest to widest): Penstemon < Physalis < Asclepias. Seeds were collected in Missouri and Illinois for Penstemon, in Missouri, Illinois, and Minnesota for Asclepias, and in Wisconsin and Minnesota for Physalis. Seeds were stratified at 1, 5, and 9°C for up to 20 weeks and then incubated at alternating (12/12 h) temperatures of 15/6, 20/10, 25/15, and 30/15ºC for 2 weeks. We calculated tolerance range using Levins’ B, where values approaching 1.0 represent a wide range and those approaching 0 represent a narrow range. Non-dormant seeds of Asclepias germinated highest at 20/10-30/15°C and those of Physalis mostly did so at 25/15-30/15°C, regardless of stratification temperature. On the other hand, highest germination of Penstemon occurred mostly at 15/6-30/15°C only following stratification at 1°C. Tolerance ranges were 0.81, 0.92, and 0.93 for populations of Asclepias from MO, IL, and MN, respectively, 0.72 and 0.70 for populations of Physalis from WI and MN, respectively, and 0.61 and 0.57 for populations of Penstemon from MO and IL, respectively. Thus, our hypothesis was supported that tolerance range (narrowest to widest) varied according to dispersal strategy: Penstemon (gravity) < Physalis (animal) < Asclepias (wind).
1 - Middle Tennessee State University, 1301 East Main St, PO Box 60, Murfreesboro, TN, 37132, USA
2 - Chicago Botanic Garden, Division of Plant Biology and Conservation, Glencoe, IL, 60022, USA
Presentation Type: Poster:Posters for Sections
Candidate for Awards:Ecological Section Best Graduate Student Poster