The structure of populations across landscapes influences the dynamics of their interactions with other species. Understanding the geographic structure of populations can thus shed light on the potential for interacting species to coevolve. Host – parasitoid interactions are widespread in nature, and also represent a significant force in the evolution of plant – insect interactions. However, there have been few comparisons of population structure between an insect host and its parasitoid. We used microsatellite markers to analyse the population genetic structure of Pleistodontes imperialis sp. 1, a fig-pollinating wasp of Port Jackson fig (Ficus rubiginosa), and its main parasitoid, Sycoscapter sp. A, in eastern Australia. Besides exploring this host – parasitoid system, our study also constitutes, to our knowledge, the first study of population structure in a non-pollinating fig wasp species. We collected matched samples of pollinators and parasitoids at several sites in two regions separated by up to 2000 km. We found that pollinators occupying the two regions represent distinct populations, but, in contrast, parasitoids formed a single population across the wide geographic range sampled. We observed genetic isolation by distance for each species, but found consistently lower FST and RST values between sites for parasitoids compared with pollinators. Previous studies have indicated that pollinators of monoecious figs can disperse over very long distances, and we provide the first genetic evidence that their parasitoids may disperse as far, if not farther. The contrasting geographic population structures of host and parasitoid highlight the potential for geographic mosaics in this important symbiotic system.

Usage notes

data file P. imperialis sp. 1 and Sycoscapter sp. A_revised microsatellite genotypes, sampling locations and dates for Pleistodontes imperialis sp. 1 and Sycoscapter sp. A

P. imperialis_cytb sequences

Alignment of cytb sequences for Pleistodontes imperialis sp. 1

P. imperialis_cytb.txt

Sycoscapter sp. A_cytb sequences

cytb sequence alignment for Sycoscapter sp. A samples

Sycoscapter_sp_A_cytb_revised.txt

P. imperialis geographic and genetic distances

Geographic and genetic distances matrices used for IBD analyses for Pleistodontes imperialis sp. 1. Distance matrices were produced using the SPAGeDI software from geographic coordinates (lat/long).

Sycoscapter sp. A geographic and genetic distances geographic and genetic distances matrices used for IBD analyses for Sycoscapter sp. A. Distance matrices were produced using the SPAGeDI software from geographic coordinates (lat/long)

P. imperialis TESS input

input file for TESS analysis of microsatellite data for P. imperialis sp. 1

Sycoscapter sp. A TESS input

input file for TESS analysis of microsatellite data for Sycoscapter sp. A