Dispersal

Joel Laboy – Seed predation by rodents on Asarum canadense: addressing the importance of ants as seed dispersers of myrmecochorous plants.  Mentor: Dr. Charles Kwit, Botany

Seed predation by rodents on ant-dispersed forest herbs has been considered a major determinant on population success. One myrmecochorous plant species, Asarum canadense,was studied in two forested areas surrounding Miami University (Oxford, Ohio, USA), to evaluate the importance of services provided by ants in preventing post-dispersal seed predation by rodents. In field experiments, depots of A. canadense seeds (N = 10 seeds/depot), inaccessible to ants, were presented to rodent seed predators to test the effects of movement in distance (i.e., 1 m away from parent plant vs. next to the parent), elaiosome removal (i.e., elaiosome removed or not removed), seed burial (i.e., buried or not buried), and their interactions on seed mortality.  One hundred twenty-eight depots (16 depots/treatment combination) were monitored daily for 7 days.  Seed predation, as measured by the number of seeds remaining, was only affected significantly by burial.  After three days, rodents had removed < 15% of buried seeds, while ~65% of unburied seeds had been removed.  After one week, > 90% of unburied seeds had been removed, while buried seeds incurred little additional mortality. Our results indicate that seeds buried by ants stand the best chance of survival during the post-dispersal/pre-germination phase of the life cycle of A. canadense.

Jake Long – The effects of domestic cat urine and feces odor on prairie vole (Microtus ochrogaster) behavior.  Mentors: Dr. Nancy Solomon and Dr. Brian Keane, Zoology

The affect of predators on prey behavior explains the nature of a prey animal. This experiment explores the behavioral changes in prairie voles (Microtus Ochrogaster) in semi-natural conditions to a domestic cat (Felis catus) predatory risk simulation. Clean litter (100% corn) was used as a control, and used cat litter (with urine and feces) was used for the stimulus. The 6 outdoor enclosures used were each bisected into 2 regions.  A region was assigned to the stimulus and one to the control. The behavior of the prairie voles was be obtained by using live trapping to determine home range size, center of activity, number of captures in the stimulus areas compared with control areas, and the number of individuals that appeared in the two areas.  This was done for a 3 week period without control or stimulus, then for 3 weeks with each enclosure containing one half control and half stimulus. The results show no significant decrease in the number of captures in the stimulus areas, and no decrease of the number of individuals captured in the stimulus areas. Since prairie voles do not exhibit anti-predatory behavior under these conditions, it can be concluded that, their behavior isn’t affected by domestic cats’ urine and feces odors.

Lea Woodard – Effect of patch size and predatory cues on colonization by herbivores.   Mentor: Dr. Ann Rypstra, Zoology

 Plant patch size and predator information have been shown to largely influence phytophagous insect movement and herbivory. This research project manipulated the patch size of green bean plants and treated patches of difference sizes with silk worm silk which has been a useful surrogate for spider cues in other studies.  The goal of this project was to determine the significance of herbivory as a result of colonization determined by patch size and application of silk worm silk. This experiment was tested using four replicate field runs comparing individual and clustered green bean plants both with and without silk worm silk. The amount of herbivory was quantified by measuring the area of leaf damage over the total leaf area to find the percent damage. The mean percent damage of all four replicates were then found and compared between the four treatments. A significant difference in amount of herbivory and colonization rate by patch size was found, but not a significant effect of silk worm silk on the amount of herbivory. The results of this project indicate that although clustered plants were colonized faster, individual plants had a higher percent herbivory than clustered plants, which is opposite of previous studies. This result could be due to the fact that during our experiment, because of weather conditions, there were few numbers of phyotophagous insects found on or around the green bean plants, which would lower herbivore density and herbivory on clustered plants.