Distribution of host crop communities
We compiled data on host crop distributions to determine how variation in host ecological communities, i.e. cultivation of specific crops, was associated with parasite specialization (Q1). As a proxy of host abundance, we considered area harvested of the three focal host species: maize, millet, and sorghum from global crop production data (Monfreda et al. 2008). These data are based on integration of national, state, and county level census statistics with global cropland cover derived from satellite imagery and provide estimates of average hectares harvested for each crop per land area of a 5 x 5 arcminute grid cell, according to multiple years of data centered on the year 2000 (Monfreda et al. 2008). We estimated relative abundance of hosts by calculating the fraction of land planted to a particular host relative to maize, millet, and sorghum combined. We also considered productivity (yield per hectare) from the same dataset (Monfredaet al. 2008). Analyses were limited to S. hermonthicaprone regions, which we defined as regions within 200 km of a known occurrence with habitat suitability scores ≥ 0.1, according to S. hermonthica environmental niche models (ENMs) constructed using occurrences on all hosts (Bellis et al. 2020).