SPECIES DISTRIBUTION MODELING AND COLD-TOLERANCE OF A FUNGUS-FARMING ANT SYMBIOSIS

Current anticipated climate change suggests that average global temperature will continue to rise and will cause species ranges to shift to higher latitudes and altitudes. In general, species that are tolerant to a wide range of temperatures and water availability will be able to adapt to changing global temperatures opposed to those who have smaller ranges. In the light of global climate change, many symbioses have been studied regarding stress-induced and adaptive evolution, however, one symbiosis yet to be thoroughly considered is that between fungal-gardening ants and their fungal symbionts. In the following studies, we lay foundation for such work. First, we created species distribution models for eight species of Trachymyrmex found within the United States. From these models, we have provided evidence that temperature is one the limiting factors within all presented species. Secondly, we have conducted cold-tolerance assays on Trachymyrmex septentrionalis, an attine species with one of the largest distributions and latitudinal clines among all fungal-gardening ants. This species is an ideal organism to investigate cold-stress adaptation, as we can evaluate cold-tolerance of both the ant and the fungus. We have concluded that both the ants and fungal cultivar have adapted to be cold-tolerant in their northern ranges. From these studies, we may be able to predict how attines, other species of ants, and insects may respond to climate change

Potential Distribution of Six North American Higher-Attine Fungus-Farming Ant (Hymenoptera: Formicidae) Species

Ants are among the most successful insects in Earth’s evolutionary history. However, there is a lack of knowledge regarding range-limiting factors that may influence their distribution. The goal of this study was to describe the environmental factors (climate and soil types) that likely impact the ranges of five out of the eight most abundant Trachymyrmex species and the most abundant Mycetomoellerius species in the United States. Important environmental factors may allow us to better understand each species’ evolutionary history. We generated habitat suitability maps using MaxEnt for each species and identified associated most important environmental variables. We quantified niche overlap between species and evaluated possible congruence in species distribution. In all but one model, climate variables were more important than soil variables. The distribution of M. turrifex (Wheeler, W.M., 1903) was predicted by temperature, specifically annual mean temperature (BIO1), T. arizonensis (Wheeler, W.M., 1907), T. carinatus, and T. smithi Buren, 1944 were predicted by precipitation seasonality (BIO15), T. septentrionalis (McCook, 1881) were predicted by precipitation of coldest quarter (BIO19), and T. desertorum (Wheeler, W.M., 1911) was predicted by annual flood frequency. Out of 15 possible pair-wise comparisons between each species’ distributions, only one was statistically indistinguishable (T. desertorum vs T. septentrionalis). All other species distribution comparisons show significant differences between species. These models support the hypothesis that climate is a limiting factor in each species distribution and that these species have adapted to temperatures and water availability differently