2011 Annual Report
1a.Objectives (from AD-416)
1: Assess treatment success of the Formosan Subterranean Termites in the French Quarter at the level of alate swarms. This study is to determine alate numbers, spatial and temporal distributions and sex-ratios of alates in swarm gregations, and infer colony numbers contributing to swarm aggregations and origins of alates from genotypic profiles. 2: Microsatellite development and population genetic studies of invasive termites by developing microsatellite markers for termite species, which already are invasive or are likely to become invasive and which pose a significant threat to agriculture or urban structures if established in the United States. We will then use microsatellite genotyping to describe population genetic structure and colony breeding systems to identify factors that facilitate invasiveness and track points of origin and paths of movement of invasive termite in the United States. The knowledge gained from this study will help to guide decisions about treatment and prevention of spread of invasive termites.
1b.Approach (from AD-416)
Alates from light traps and workers from inground stations, infestations of trees and structures that are active during the respective swarm season will be collected throughout the French Quarter of New Orleans with the assistance of USDA/ARS and New Orleans Mosquito and Termite Board (N.O.M.& T.C.B). The alates will be counted, sexed and stored and each colony will be identified by its genotypic profile. This allows us to test whether the alates originate from colonies in the vicinity of their capture and establish how often the same colonies swarm during a swarm season and over the years, and how far alates from a particular colony fly. Microsatellite development: DNA will be extracted and digested with restriction enzymes from at least 20 termites per colony from at least 20 colonies per population and multiple populations per geographic region. Protocols for microsatellite genotyping will be optimized for each species. Samples will be assigned to colonies and the breeding system (simple or extended family) and degree of inbreeding will be determined for each colony. Population genetic structure will be described using F-statistics. Genetic distances among colonies and populations will be used to track origin and spread of invasive termites.
Alates (winged termites) were collected in 2007, 2008 and 2009 for the duration of the swarming season (April to July) via 17 bucket traps attached to light sources throughout the French Quarter of New Orleans. The alates were counted, sexed, and stored in 95% ethanol. Sample groups consisted of 20 male and 20 female alates from each of 5 traps which contained high alate numbers (>50 each) at 2 to 7 peaks (swarm events) within each swarming season during the three year study period. Deoxyribonucleic acid (DNA) was extracted from individual alates, and microsatellite genotyping was used to determine relatedness among alates, based on which, the number of colonies contributing alates to traps was inferred. We calculated the numbers of colonies contributing alates across locations (traps) and times (peaks within the same swarm season and between seasons). The number of colonies contributing to each trap was highly variable over time and there was no consistent “hot spot” of high colony numbers in any particular trap.
The most important finding of the long-term monitoring of the composition of alate swarms, using genetic data, is that the number of colonies contributing alates to swarms has decreased over time. Specifically, colony numbers contributing alates to light traps have dropped from an average of 13 colonies per trap per peak in 2003 to 7 in 2007 and only 2 per trap and peak in both 2008 and 2009. Colony numbers combined across locations (traps) per peak similarly decreased from 14 in 2007 to only 4 in both 2008 and 2009. Calculated across all traps and peaks per year, colony numbers contributing alates to traps decreased from ~34 in 2007 to 17 in 2008, and then decreased further to only 8 colonies in 2009. This is proof that the effective population size, i.e., the number of colonies producing alates, has been significantly reduced, in all likelihood due to the persistent treatment effort.
In addition, calculating nestmate proportions shared among traps during the same swarm event and across all time points showed that the same colonies can contribute alates to more than one trap during more than one peak and in more than one year. Thus, although the overall number of colonies has undoubtedly decreased, even a few colonies may effectively maintain what appears to be a residual level of alate activity.
Progress in this project is monitored through Annual FST Technical Committee Meetings, reports, regular meetings with cooperators, routine phone calls, and e-mail correspondence.