Meta-population dynamics and evolution of Diachasmimorpha tryoni (Hymenoptera; Braconidae), a purposefully released parasitoid of ceratitis capitata (Diptera: Tephritidae), in Hawaiʻi

Abstract

The meta-population and evolutionary dynamics of the Australian biocontrol agent Diachasmimorpha tryoni, a parasitoid of Ceratitis capitata, was investigated due to its association with a non-target host, Eutreta xanthochaeta and competitive interaction with Fopius arisanus in Hawaii. Twelve polymorphic microsatellite loci were characterized and used in combination with sequence data to profile D. tryoni's evolution within Hawaii and between Hawaii and Australia. Using both contemporary and historic collections it was found that D. tryoni has evolved significantly from its founding population, but no predicted population was significantly associated with that of the non-target host. The interaction between D. tryoni and its competitor was assessed using a combination of population genetic inference and ecological niche modeling techniques. This interaction was shown to have the greatest evolutionary influence on D. tryoni in Hawaii through competitive exclusion into upper elevation habitat, as characterized by E. xanthochaeta. Augmentative releases of D. tryoni were also genetically modeled using museum specimens to assess the influence that a mass release may have on the evolutionary dynamics of a naturalized population. The majority of individuals post-augmentation were found to be genetically associated with the released population, but hybridization between the two populations was observed. This data also implies local population recruitment and population genetic structural dilution, suggestive of a Reverse Bottleneck following augmentation. The influence of heterosis on the interaction between mass released and naturalized D. tryoni was also measured. Employing a combination of mate selection trials, molecular genotyping, and fitness measurements, our results were capable of documenting the hybridization of the released and wild populations, the fitness of the hybridization interaction, and female mate choice. These analyses reveal that the interactions between two moderately differentiated populations, as would be the case during an augmentative release, are significant. The techniques employed herein can be used to understand the influence a competing organism, or a mass released agent, may have on a biocontrol agent prior to both classical, or augmentative biocontrol introduction.