Recent models suggest a relationship exists between community diversity and pathogen prevalence, the proportion of individuals in a population that are infected by a pathogen, with most inferences tied to assemblage structure. Two contrasting outcomes of this relationship have been proposed: the “dilution effect” and the “amplification effect.” Small mammal assemblage structure in disturbed habitats often differs from assemblages in sylvan environments, and hantavirus prevalence is often negatively correlated with habitats containing high species diversity via dilution effect dynamics. As species richness increases, prevalence of infection often is decreased. However, anthropogenic changes to sylvan landscapes have been shown to decrease species richness and/or increase phylogenetic similarities within assemblages. Between January 2011 and January 2016, we captured and tested 2406 individual small mammals for hantavirus antibodies at 20 sites across Texas and México and compared differences in hantavirus seroprevalence, species composition, and assemblage structure between sylvan and disturbed habitats. We found 313 small mammals positive for antibodies against hantaviruses, evincing an overall prevalence of 9.7% across all sites. In total, 40 species of small mammals were identified comprising 2 taxonomic orders (Rodentia and Eulipotyphla). By sampling both habitat types concurrently, we were able to make real-world inferences into the efficacy of dilution effect theory in terms of hantavirus ecology. Our hypothesis predicting greater species richness higher in sylvan habitats compared to disturbed areas was not supported, suggesting the characteristics of assemblage structure do not adhere to current conceptions of species richness negatively influencing prevalence via a dilution effect.

The fungus Ustilago maydis produces galls or tumors on corn ears called corn smut or huitlacoche. Used for human consumption in several countries for its nutritional and sensory traits, huitlacoche is considered a delicacy in Mexican cuisine and has a significant economic value. Hybrid U. maydis strains are regularly used for the large-scale production of huitlacoche; however, depending on the genetic characteristics of the parent strains, the pathogenicity and infection rate of hybrid fungi are often suboptimal due to compatibility issues between different strains. Using double-loaded organisms is common in agriculture to improve product characteristics, performance, and shelf-life. A methodology to obtain unicellular U. maydis strains with a double genetic load (n + n) capable of producing galls on corn ears without mating (hybridization) is reported herein. This methodology resulted in 206 U. maydis isolates. Screening showed that 147 corn plants (>70%) underwent infection and gall production. Of the 147 gall-producing U. maydis strains, those with the highest field performance were selected. Three strains, Um-UAEMor-78 (yielding 21.65 ton/ha), Um-UAEMor-120 (22.31 ton/ha), and Um-UAEMor-187 (22.99 ton/ha), showed higher yields than the control strain, CP-436(a1b1) × CP-437(a2b2) (17.80 ton/ha). A specific methodology to obtain unicellular U. maydis strains with a double genetic load capable of infecting baby corn ears and forming galls is described for the first time, providing a novel alternative for producing huitlacoche and helping to improve the yields and morphological traits of galls.