High-speed seeds: The ballistic seed dispersal of Claytonia perfoliata

Background/Question/Methods Claytonia perfoliata (Portulacaceae) is a widespread annual forb found throughout western North America. Previous research has shown that it uses diplochory in its seed dispersal, which includes ballochory followed by myrmecochory. The ballistic mechanisms of other species in the genus were first described in 1892. This description included the basic mechanisms behind the dispersal, but was purely qualitative. The goal of this ongoing study is to determine the distances of dispersal and physical characteristics of C. perfoliata to confirm the previous findings pertaining to Claytonia. Through microscopy, computer modeling, tests for material and physical characteristics, and stroboscopic photography this study will help to better understand the ballistic dispersal mechanisms of C. perfoliata. Thus, we can better understand the potential ranges with which the species can be distributed, and how this dispersal may affect competition between individuals and succession in local communities. Seeds of C. perfoliata were sourced from local populations in Weber County, UT. These seeds were stratified in a freezer for approximately 8 weeks, and germinated using G3 and at a temperature below 15.5° C. Seeds produced by this generation were filmed during dispersal beneath a dissecting microscope at 240 fps.

Results/Conclusions Preliminary observations confirm some of the previous findings concerning the mechanics of dispersal in other species of Claytonia. We attempted to observe the initial velocity of the seeds by filming at 240 fps through a dissecting microscope and subsequently tracking the seed position through analytical software. This attempt failed to yield results due blurring on the frames from the high speed of the dispersal. Continuing experiments into the physiology behind the dispersal will include testing the coefficients of static and kinetic friction between the valves and the seeds, as well as between seeds, in order to quantify the previous findings. Other experiments will include a two-camera method of capture using stroboscopic photography to better determine the initial velocity of the seeds following dispersal, and thus calculate initial kinetic energy. The above experiments will be following the methods of ballistic seed dispersal measurement used by a previous researcher on the subject of ballochory in other herbaceous species. The results will be used in a model to determine the potential distribution of individuals within the species by ballochory alone.