Location: Southern Horticultural ResearchTitle: Development of microsatellites for population genetic analyses of the granulate ambrosia beetle
|HUSSENDER, CLAUDIA - Louisiana State University Agcenter|
|PARK, JONG-SEOK - Louisiana State University Agcenter|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2017
Publication Date: 6/1/2017
Citation: Hussender, C., Park, J., Werle, C.T., Adamczyk Jr, J.J. 2017. Development of microsatellites for population genetic analyses of the granulate ambrosia beetle. Journal of Economic Entomology. 110:1107-1112.
Interpretive Summary: The granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky) is an important threat to the profitable production of ornamental nursery crops throughout the eastern and southern United States. The objective of our study was to isolate and characterize genetic markers as tools to investigate the breeding system, family structure, population genetics and speciation. We collected beetles from different sites in south Mississippi and discovered molecular markers that clearly separated the beetle populations. These molecular markers developed in this study addressed important basic and applied questions related to X. crassiusculus’ biology and pest status. For example, genetic analysis will be used to test hypotheses concerning breeding structure (monogamy vs. polygamy, frequency of mating with related males), family structure (relatedness of females and offspring infesting the same or different trees, number of offspring per female, etc.), and large-scale gene flow and population genetic structure. The latter aspects have important implications on identifying origins of infestations, modes of dispersal (natural dispersal by flight vs. human transport) and prevention of spread of this invasive species.
Technical Abstract: Limited male dispersal and local mating in ambrosia beetles are expected to result in extreme inbreeding and highly structured populations. In this study, we developed microsatellite markers for the granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky) for use in future studies into population and family structure of this invasive pest species. We employed de novo next-generation sequencing to generate whole genome shotgun sequences for the characterization of microsatellite loci. Approximately 6% of the 84,024 contigs generated from Hi-Seq Illumina 2x250bp sequencing contained microsatellites with at least four repeats of di-, tri-, tetra-, penta- and hexamers. Primers were synthesized for 40 microsatellite loci with trimer repeat units. Twenty four primer pairs yielded consistent PCR products of unique loci and were validated for population genetic application using three samples of X. crassiusculus from Mississippi. Thirteen loci were found to be polymorphic with up to five alleles per population. The two beetle samples from Pearl River County (Poplarville and McNeill) belonged genetically to the same population. The population from Lamar County (Purvis) was genetically distinct, separated by a moderate genetic distance (FST = 0.11) and five unique alleles (with > 5% frequency). Consistent with the perceived mating structure (incest of females with flightless males) the populations showed homozygote excess at most loci as indicated by the coefficients of inbreeding (FIT = 0.45 and FIS= 0.37) and high mean relatedness among individuals (r = 0.15).