AVIAN DISPERSAL OF THE ACTINOMYCETE FRANKIA ACROSS A BARRIER ISLAND LANDSCAPE

In the nutrient-poor soils characteristic of coastal environments, symbiotic association with the nitrogen-fixing root endosymbiont Frankia is essential to establishment and survival of the woody shrub Morella cerifera. Nutrient deficiency quickly becomes severe unless seedlings are infected by Frankia soon after germination. However, the means of arrival of Frankia prior to shrub establishment has not been determined. Using sterilized lab-grown M. cerifera seedlings and fecal samples collected from passerine birds on the Eastern Shore of Virginia, viability of avian dispersal of the bacteria was tested. Although passerine fecal samples did produce nodules on some sterilized M. cerifera seedlings, these experimental inoculations did not lead to significantly higher likelihood of nodulation, relative to sterilized reference seedlings. Non-sterilized seedlings displayed greatest percent nodulation; results suggest that passerines contribute to Frankia dispersal, but also that the actinomycete is contained on or within viable seeds or fruits of M. cerifera, and therefore may be co-dispersed directly from the parent plant