Range limits, symbiont diversity and specificity in fungus-gardening ants

The fungus-gardening ants are well-known members of lowland neotropical ecosystems. Many fungus-gardening ants however reach well into the temperate zones of North and South America. For example, the genus Trachymyrmex is primarily a temperate genus with most species found in northern Mexico and the southern US. Some theory predicts reduced genetic diversity and host-symbiont specificity along range margins, such as those found in the US. We tested these predictions in three species of Trachymyrmex by using a variety of Sanger based (COI, ITS and microsatellite) markers and genotyping by sequencing approaches. We did not find much evidence of reduced genetic diversity or relaxed patterns of host-symbiont specificity.