Global fire cycles are being altered by the introduction and spread of invasive grasses. These changing fire regimes are resulting in state changes in arid systems from native shrubland, to invasive grass monocultures, which perpetuate the invasive grass fire cycle. It is thought that biotic resistance provided by rodents help mitigate the affects of this cycle through granivory. This also raises the question, do rodents have a preference for native or invasive seeds? And how do seed traits influence granivory? In 2018, we looked at the influence rodents had on the fate of native and invasive seeds in the Mojave Desert by providing a set number of seeds in petri dishes for different seed species in burn, re-burn and rodent exclusion treatments over a two week period. Once the dishes were collected back in, we determined the number of remaining seeds in each of the dishes from the various treatments.
Results/Conclusions
The results suggest that rodents play a large role in the establishment success of both native and invasive seeds. The number plots was significantly lower than the seeds remaining in exclusion plots for every species. Overall, seeds were approximately 30% more likely to be taken in plots where rodents were allowed, regardless of whether they were native or invasive. This pattern still stands, but is less apparent, when looking at seeds of a smaller size, suggesting that rodents are less attracted to small seeds. This is in line with the optimal foraging theory which assumes that an animal will adopt a foraging strategy which provides the highest benefit for the lowest cost. These results suggest that seed size and texture may have a stronger influence on rodent seed selection than origin (invasive vs. native).