Post by research students (Fall 2017)
During the Fall 2017 semester, we conducted ant surveys from six grass plots and six pavement plots, both at the Statesville and Mooresville campuses of Mitchell Community College. Besides wanting to know what types of ants were living in each location, we were also interested in looking for differences among plot types and across the two campuses.
As you can see from figures 1 and 2 the grass plots in Statesville were different in composition from the grass plots in Mooresville. Red-imported fire ants (Solenopsis invicta) dominated Mooresville plots while thief ants (Solenopsis molesta) dominated the plots in Statesville. There are probably many reasons for this. One simple explanation may be that the Statesville campus provides a more suitable habitat space for the thief ants.
Thief ants and red-imported fire ants are closely related, belonging to the same genus. It seems that when they do interact, thief ants play the role of antagonists. These thieves can infiltrate and go undetected in a fire ant colony. They can then steal the young fire ants, destroy a small group of workers, and prey on the queens. As a red-imported fire ant, you would do well to avoid nesting in areas with a high density of thief ants. This could easily explain why we did not trap any fire ants on Statesville’s campus.
As figures 3 and 4 show, little black ants (Monomorium minimum) dominate the pavement plots on both campuses. This is no surprise when you realize that these tiny creatures can nest just about anywhere. There brooding chambers are typically shallow, reaching depths of only 5 cm. Maybe they were just the fastest to our bait stations.
Fig. 5 and 6 show how many plots we needed to use in each of the habitats to reach a maximum diversity (shown here as Simpson index). We used six replicates of each which looked to be adequate.
Diversity indices often take into account both how many different species there are in an area and also the number of each type of species. We used the Simpson index and then converted that into what is called true diversity, or the effective number of species. That is what is reflected on the y-axes of figures 7 and 8. What is interesting is that when we compared the grass plots and pavement plots of both campuses, there was no significant difference (Fig. 7). However, when we compared the overall diversity of the Statesville campus with the Mooresville campus (Fig. 8), there was significance (p=0.039). Statesville had a higher diversity of ants when compared with Mooresville.
You can figure out whether that’s good or bad.