Pendleton, Rosemary , Pendleton, Burton K. .
Seed heteromorphism in Cryptantha section Krynitzkia: geographic patterns, germination, and dispersal.
The Krynitzkia section of Cryptantha contains all annual North American species. Most species produce 4 equal nutlets per flower, but some are heteromorphic; 3 nutlets readily dispersing while one remains attached to and disperses with the calyx. In still others, the number of nutlets per flower has been reduced from four to one. The relative distributions of single-, homomorphic- and heteromorphic-seeded species differ. Patterns in geographic distribution are likely related to geographic weather patterns and environmental heterogeneity. Single-seeded species occur in the far western United States, generally at lower altitudes, where summers are hot and dry and precipitation comes mainly during the winter months. Homomorphic species are proportionately more common at higher latitudes and elevations where soil moisture may be more abundant and predictable. In contrast, heteromorphic seed producers occur in the interior west, the highest proportion occuring in Kansas and Oklahoma, with declining frequency as one moves west. Heteromorphic-seeded species may be associated with early summer storm patterns occurring where warm moist Gulf air meets cold Canadian air and dry air from the Rockies, creating a bimodal moisture pattern. We have studied germination and dispersal patterns in the heteromorphic annual, Cryptantha crassisepala. Deciduous nutlets germinate to a higher percentage and at a faster rate. They also have a have broader temperature range for germination. Data suggest a High Risk-Low Risk strategy, with persistent nutlets being more conservative in germination. Persistent nutlets have approximately 3 times the mass, and are consistently more dormant than deciduous nutlets. They also disperse further, whether by wind-caused tumbling or attachment to animal fur. Once germinated, persistent nutlets have greater survival rates, flower earlier, and produce more seed. Additional data on seed banking and emergence phenology should produce sufficient data for the modeling of dual fitness sets.
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1 - USDA Forest Service, Rocky Mountain Research Station, 333 Broadway SE, Suite 115, Albuquerque, New Mexico, 87102-3497, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM