I got this link to "17,000 Species in the Great Smoky Mountains. And Counting" (http://www.metropulse.com/news/2011/nov/16/17000-species-great-smoky-mountains-and-counting/) from my native plant listserv courtesy of Jeffrey Caldwell, along with an interesting observation from that report:
“...most of the plant species that you see in the Great Smoky Mountains National Park rely on ants to disperse their seeds,” Sanders says. “So one of the things we did was just put out seeds and look at what happened to them. And 166 out of 167 times, one ant species carried the seed away. So even though there there’s a lot of biodiversity in the Smokies, there’s some species that do a lot.” If one of those super-species was threatened by changes in its habitat, it could have wide-ranging consequences.
Most native plant fanciers appreciate the role of insects in the food web, but the role of ants was previously unknown to me. I seem to recall that a native (and distinctly larger) black ant was more plentiful when I was growing up, but I have hardly seen them recently. I think they've been supplanted by Argentine ants all along the western coast of the US.
Wikipedia confirms that Argentine ants win battles for turf from native ants simply because they act as one continental-wide (actually a global) hive*. An illustration of this is that if you take an Argentine ant from San Diego and drop it into a hive in Los Angeles, it will fit right in. I don't think our native ants have this advantage: an interloper from another hive will be killed. So ultimately Argentinian ants will win turf battles by virtue of their overwhelming numbers and disinclination to fight among themselves.
The ants' reduced genetic diversity, from the small population of ants that initially invaded the U.S., allowed a giant "supercolony" of closely related ants to grow unchecked from San Diego to Ukiah, 100 miles north of San Francisco.link
Apparently, in their native areas they are not as populous as they are in California. Researchers suspect this is due to hive competition. I wonder if we could find or cultivate a sufficiently different Argentine ant, release it into the "wild" and that would keep the species in check by internal warring?
So there's the seed dispersal issue: I'll bet Argentine ants don't disperse seed as well as our native ants. But there's also other food web issues:
In a series of laboratory experiments [scientists showed that] baby horned lizards fed a diet of insects typical of a community after invasion of Argentine ants cannot grow and, in many cases, decline in weight. But when their diet is switched to insects typical of an uninvaded community, the scientists found that the baby horned lizards grow normally. link
So maybe the sign of a really robust Ca native ecosystem is no Argentine ants?
*Wikipedia: According to research published in Insectes Sociaux in 2009, it was discovered that ants from three Argentine ant supercolonies in America, Europe, and Japan, that were previously thought to be separate, were in fact most likely to be genetically related. The three colonies in question were one in Europe, stretching 6,000 km (3,700 mi) along the Mediterranean coast, the "Californian large" colony, stretching 900 km (560 mi) along the coast of California, and a third on the west coast of Japan.
Based on a similarity in the chemical profile of hydrocarbons on the cuticles of the ants from each colony, and on the ants non-aggressive and grooming behaviour when interacting, compared to their behaviour when mixing with ants from other super-colonies from the coast of Catalonia in Spain and from Kobe in Japan, researchers concluded that the three colonies studied actually represented a single global super-colony.
The researchers stated that "enormous extent of this population is paralleled only by human society", and had probably been spread and maintained by human travel