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Neuroterus saltatorius is a gall wasp that has expanded its range poleward in North American western oak ecosystems as a result of anthropogenic change and is outbreaking in its expanded range. This research compared its interactions with parasitoid wasps and its host plant between the native and expanded ranges to uncover how altered interactions contribute to outbreaks. This study investigates relationships between gall size, survivorship, and parasitism. We determined the survivorship and gall size of 2,259 galls in 12 native and expanded range sites, using R Studio to compare mean and variation of gall size and survivorship between regions. Native region trees have more intraspecific variation in size and survivorship with a lower mean survivorship. This suggests that trees in the native range are more resistant and potentially more diverse. Gall size is larger in the expanded range and in parasitized galls, and failed galls are smaller than survived galls.



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Variation in Gall Size Between the Native and Expanded Range of a Range-expanding Gall Wasp Mediates Interactions and Influences Survivorship