Hannah A. Veltkamp, Sydney Houghton, Michael T. Stevens (Utah Valley University)
Faculty Advisor: Stevens, Micheal (Utah Valley University, Biology)
Netleaf hackberry (Celtis reticulata) is a deciduous shrub native to the southwestern United States and northern Mexico. Individual shrubs can be long-lived, but newly established stands of hackberry are rare. The lack of juvenile hackberry in the wild could be due to low germination rates reported in both laboratory and field settings. The seeds of hackberry are embedded in drupes that are an important source of food for birds and small mammals. Animals likely play an important role in seed dispersal, and passing through a digestive tract could increase the germination rates of hackberry seeds. Passage through the digestive tract of a mammal can increase the germination rates for some plant species, but not for others. We hypothesized that passage through the digestive tract of a coyote would increase the germination rates of C. reticulata. To test this hypothesis, we collected 17 coyote scats containing visible hackberry fruits from along the Bonneville Shoreline Trail east of Provo, Utah, using latex gloves. Each scat location was recorded using a GPS unit. After collecting each scat, we found the closest hackberry shrub and picked a sample of fresh hackberry fruits from it. All samples were cleaned and cold stratified and then planted into cone-tainers containing a potting soil mix and placed in the Utah Valley University greenhouse. We sowed 20 seeds from each of the 17 coyote scats and
20 seeds from each of the neighboring hackberry bushes for a total of 680 seeds. The 680 cone-tainers were labeled with plastic stakes and randomly positioned into trays that were randomly distributed on a bench in the greenhouse. The seeds, and later seedlings, were watered as needed (typically three days/week). On watering days, we checked for newly-germinated hackberry seedlings and recorded their date of emergence. Near the end of the experiment, we measured the height of each seedling. The germination rate of hackberry seeds that had passed through the
digestive tract of a coyote did not differ from the germination rate of seeds from fresh-picked fruit (42.7% vs. 46.5%, respectively; _ 2 = 0.558, df = 1, p = 0.455). However, on average, the coyote-treatment seeds took just over half as many days to germinate as did the seeds from fresh-picked (undigested) fruit (35 days vs. 69 days, respectively; p < 0.001). The seedlings from coyote-treatment seeds were 9.5% taller than were the seedlings derived from seeds from undigested fruit (6.4 cm vs. 5.8 cm, respectively; p < 0.001). Our results show that consumption by coyotes can benefit hackberries by enabling their seeds to germinate earlier in the year when
conditions for establishment are good. The earlier start on germination that coyote-ingested hackberries get translates to increased height and likely a higher rate of survival in the field.