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This is the first study in cycads to measure genetics, demography, and survival of plant populations due to an invasive insect. The armored scale Aulacaspis yasumatsui invaded the island of Rota in 2007 posing a new threat to the native Cycas micronesica population. The pre-invasion genetic structure of the host plant populations revealed considerable genetic variation and restricted gene flow among habitats and identified genetic clusters representing the genetic variation of the species in Rota. Prior to localized A. yasumatsui infestations, 28 permanent plots were established among seven locations in 2008. Data were collected to document survival and demography until 2023. There were 11,254 stems per ha in 2008, 9.2% of which were adult trees. The seedlings rapidly reached 100% mortality, and no seedlings were observed in the plots from 2014 until 2023. There were 149 stems per ha in 2023, 100% of which were adult trees. This invasion behaved similarly to the invasions of other islands, with the native cycad population reaching 98.6% mortality of the entire population and 85.6% mortality of the adult tree population within a 15-year span. Mean stem height was only 30 cm in 2008 because of the majority of the population was seedlings and juveniles. Mean stem height gradually increased with each successive year of data collection due to selective mortality of the small plants, and was 245 cm in 2023. Mean leaf number per adult tree was 83 in 2008, abruptly declined to a low of 8 in 2013, then gradually increased to 20 in 2023. Incidence of the herbivore rapidly increased to a peak in 2011 before stabilizing to about 40% to 50% of the soft organ surfaces. The invasion of this insular cycad population by A. yasumatsui caused selective mortality of the smallest plants, and the population-level mortality was more rapid than the prior invasion of nearby Guam. These combined results provide a genetic baseline and population structure benchmark for future conservation protocols during species recovery efforts. The geographically separated and genetically isolated populations indicate this cycad species remains highly vulnerable to localized extirpations, as the unique alleles from extirpated habitats are at risk of being lost forever.