Metapopulations are a group of populations linked by among-population dispersal. Source-sink model has been used in theoretical studies to understand role of habitat quality in affecting population dynamics. However, few source-sink metapopulations had been probed empirically. Pollinating fig wasps and their host fig trees form obligate mutualism systems. Fig wasps are weak fliers but can use wind currents disperse to a long distance. Previous studies indicated that the pollinating wasp (Wiebesia sp. 3) is a weak competitor compared to Wiebesia pumilae, and was remanent on some islands. Wiebesia sp. 3 co-occurs with W. pumilae on most islands, except on a most isolated island. This island locates at the most southeastward and upwind when fig wasps emerge, thus W. pumilae could not arrive. We assumed that Wiebesia sp. 3 on the most isolated island serves as a source and export fig wasps to other islands and maintain the co-occurrence with W. pumilae. In this study, using microsatellite markers we genotyped samples of a group of island populations of a pollinating fig wasp (Wiebesia sp.) of Ficus pumila. We also estimated effective population sizes and emigration and immigration rates as well as net migrant of each population.
Results/Conclusions
Moderate to high genetic diversity was found in each population. Genetic differentiation to the most isolated island population was higher than differentiation among the remanent populations. However no obvious genetic structure among the islands was found. Based on the emigration and immigration, the isolated island population was source in historical and contemporary generations. Another island population was also a source population but not in historical generations. Several other islands populations, some were source in historical but receptive in contemporary generations. Based on genetic structure, our findings confirm the source-sink dynamics in these island populations of Wiebesia sp. 3. However the sink populations formed patchy populations linked by strong gene flow.