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It has become increasingly clear that waterways facilitate the invasion process for many species, including terrestrial species, such as ants (Walker 2006). The underlying reason may be directly related to transportation, as in the case of the red imported fire ant, Solenopsis invicta Buren whose colonies can spread by rafting on moving water (Banks et al., 1981). In other instances, periodic flooding along riparian courses often creates disturbance regimes, which promote invasions (Ellis et al., 2001). Additional habitat considerations include elevated soil moisture (Holway et al., 2002) and high productivity associated with riparian ecosystems (Kennedy 1998, Paetzold et al., 2006). These conditions are likely to promote high colony growth rates and an associated higher propagule pressure, furthering the invasion process. Ants that are predisposed to be around water are more likely to be able to take opportunistic advantage of waterways for their dispersal (Suarez et al., 2005). Many Solenopsis species, especially the most widely distributed species, commonly forage around water (Wilson 1986). The black imported fire ant, for instance, has been found preying on tubeworms exposed during low tides (Palomo et al., 2003), while S. invicta is considered a threat to wildlife in wetland habitats (Freed and Neitman 1988). The latter study noted that the fire ants were able to extend their reach into the pond by utilizing unspecified vegetation as a walkway but gave no additional details. This note offers further information as to the use by fire ants of floating vegetation as natural roads. In June of 2002, I first observed S. invicta workers crossing long leaf pondweed, Potamotegon nodusus leaves lying on the water surface of a manmade lake in Lee County, TX (N30.14, W96.88). Potamotegon nodosus is a fast-growing aquatic plant that forms extensive platforms of networked leaves on the water surface of the littoral zone. In the situation observed, these platforms were growing in an emergent area of the lake with seasonal inundation. I was able to observe the ants closely out over the water because of the presence of a 15m long raised pier that paralleled the pondweed. Many of my observations were made using a Sony PCV DCR-TRV9. Volume 118, Number 5, November and December 2007 527 |
