Abstract Detail

Ecological Section

Ridma Bandara , J K [1], Walck, Jeffrey [2], Hidayati, Siti [1], Havens, Kayri [3].

Temperature ranges for dormancy loss and germination differ between dispersal strategies along a mid-western North American latitudinal gradient.

Seed dormancy loss and germination are critical stages in plant regeneration. Each stage has an optimum temperature condition and minimum and maximum thresholds (hereafter, tolerance range). These ranges presumably vary within and among populations and determine the responses of species as the climate changes.  In addition to species-specific differences, tolerance ranges may be influenced by neighborhood sizes.  For example, species with small neighborhood sizes (i.e. limited dispersal) are expected to be more specialized to local climate conditions and have narrower tolerance ranges compared to species with a large neighborhood size. To fully comprehend population responses to climate change, it is vital to understand tolerance ranges of populations.  However, tolerance ranges have been recorded for very few species and often for only one population.  We selected two eastern North American genera contrasting in dispersal strategies and presumably in neighborhood sizes (small vs. large): Penstemon digitalis (gravity dispersed) and Asclepias syriaca (wind dispersed).  Both of these species are widespread and relevant for contemporary and future restoration of landscapes.  We hypothesized that temperature tolerance ranges for cold stratification and germination would differ among populations within each species and be positively related to their presumed neighborhood size.  Seeds of Asclepias were collected from Missouri (38°N), Illinois (41°N), and Minnesota (44°N), and those of Penstemon from Missouri (38°N) and Illinois (41°N). To examine the range of dormancy loss and germination, seeds were stratified at 1, 5, and 9°C for 0 (control) and 12 weeks and then incubated at alternating (12/12 h) temperatures of 15/6, 20/10, 25/15, and 30/15ºC for 2 weeks. Germination for fresh seeds of Penstemon from both locations was low across the incubation range.  In contrast, the incubation range at which high germination occurred for fresh Asclepias seeds widened from south to north: none from Missouri, 30/15°C from Illinois, and 20/10-30/15°C from Minnesota.  Stratification at 1°C caused the most dormancy loss (compared to 5 and 9°C) across the broadest set of temperatures in seeds of Penstemon from both locations.  In contrast, 1, 5, and 9°C caused the most dormancy loss in seeds of Asclepias regardless of location.  Thus, tolerance ranges for dormancy loss and germination differed among populations of Penstemon and Asclepias.  Although the tolerance range of Penstemon (presumed small neighborhood size) was narrower than that of Asclepias (large neighborhood size), populations of Asclepias were more differentiated than those of Penstemon.     

1 - Middle Tennessee State University, Biology, 1301 East Main st, P.O.Box 60, Murfreesboro, TN, 37132, United States
2 - Middle Tennessee State University, Biology, 1301 East Main st, P.O.Box 60, Murfreesboro, TN, 37132, USA
3 - Chicago Botanic Garden, Division of Plant Biology and Conservation, Glencoe, IL , 60022, USA

Keywords:
Climate change
Penstemon digitalis 
Asclepias syriaca.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PEC038
Abstract ID:753
Candidate for Awards:None