Filename: 1_Population_growth_rate.xlsx Variables: 1. Source host - the plant species from which experimental females were transferred 2. Target host - the plant species to which experimental females were transferred 3. Generations - tested time period, in generations 4. N0 - the number of females placed at the beginning of the experiment 5. N - the number of mites (being a progeny of N0 females) counted after each tested time period Filename: 2_Emigration_dispersal.xlsx Variables: 1. Source host - the plant species infested by mites and exposed to wind 2. Target host - the plant species toward which mites could disperse 3. N - population size on the source host 4. D - the number of individuals that dispersed from the source host Filename: 3_Emigration_acceptance.xlsx Variables: 1. Source host - the plant species from which experimental females were transferred 2. Target host - the plant species to which experimental females were transferred 3. N - the number of females placed on the experimental arena 4. R - the number of females that stayed on the experimental arena after incubation Filename: 4_Experimental_evolution.xlsx Variables: 1. Regime - host selection regime (W - wheat; B - brome; WB - wheat-brome alternating each three generations on each host species) 2. Generations - the number of generations the population survived 3. Status - 0 - censored observation; 1 - observed event of extinction Filename: 5_Field_database.xlsx Variables: 1. Sampling date - date of plant collection in the field 2. Day - the day of the year when the sample was collected 3. Year - the year of the sample collection 4. Host - the plant species collected 5. n - the number of all plant shoots examined 6. k - the number of plant shoots infested

The study was supported by the National Science Centre, Poland (NSC); research grant no. 2017/27/N/NZ8/00305 (tasks: assessing the population growth rate and host acceptance; experimental evolution); NSC research grant no. 2016/21/B/NZ8/00786 (tasks: establishing the stock population - including field work, barcoding and maintaining; assessing the dispersal rate). AL scholarships were funded by European Social Funds POWR.03.02.00–00–I006/17, NSC (PhD scholarship no. 2019/32/T/NZ8/00151) and Adam Mickiewicz University Foundation (awarded in 2019/2020). LK was involved in this work while supported by the NSC grant 2018/29/B/NZ8/00066. SMe became involved in this work while supported by a US Fulbright Scholarship.