A reason why community fluctuations in ant populations are unknown starts with the issue of identification. Alex Smith et al, ponder in their recent publication whether DNA barcoding of ants would help solve the problem. They do this by identifying ants to the generic level and then use a single gene (cytochrome oxidase 1) to identify species richness. A few more pilot studies like these should reveal the efficacy of the system to measure species richness.
from: Smith et al (2005), Phil Trans R Soc B 360, 1825-1834.