I'll admit that my knowledge of mosquitoes is not great, but I wouldn't necessarily go so far as to label them a keystone species. Since there are several different genera of mosquitoes in North America (let alone species!), is the term keystone "species" even appropriate? Can the concept be extended to higher taxa (i.e. if we remove this genus, family, etc., will it have an effect on the ecosystem disproportionate to its abundance?). If so, what becomes the basis for comparison (seeing as different genera may have vastly different numbers of species, and so on)? Most importantly, mosquitoes are generally rather abundant, and so I would suspect that any impacts that mosquito declines would have on a given ecosystem are a result of the loss of such an abundant organism as opposed to an organism that affects its ecosystem "disproportionately relative to its abundance" (the definitition of a keystone species).
Assuming, however, that the keystone "concept" can be applied to mosquitoes, could they be labeled as such? While mosquitoes are certainly an ecologically important species, I would expect not. To me, a keystone species evokes imagery of an ecosystem collapsing when it is removed (much like a stone arch would collapse if it's keystone were removed). Textbook examples include the removal of wolves resulting in overpopulation of deer and elk, which results in extensive mortality of browse vegetation (notably Quaking Aspen), and declines in sea otters leading to explosive overabundance of sea urchins which essentially "clear cut" kelp beds. As far as I know, mosquito predation or parasitism doesn't play a significant role in keeping any other species in check. Mosquitoes are an important prey item for numerous species, so perhaps they can qualify for this reason. However, many mosquito predators are not mosquito specialists (frogs, birds, bats), and if mosquitoes disappeared from an area these predators would simply prey more extensively on other species. I guess the biggest issue that I have with the notion is that, from what I understand, keystone species are a rare phenomenon but most common in low diversity communities where, if the keystone is removed, no other species is present that can fill the niche. As far as I know, Diptera (or any biting insects and/or insects with aquatic larvae to serve as a similar prey base) are ubiquitous and species-rich throughout North America (except perhaps in the Arctic). I would suspect that the declines of other species in Alamosa are more likely a result of the non-selectivity of the insecticide(s) used, or a combination of other unknown phenomena, rather than the absence of mosquitoes as the primary cause (though it may certainly contribute). Of course I won't claim any of my statements to be conclusive, or even highly probable; I'll defer that to entomologists, particularly those with extensive knowledge of mosquito ecology. Good discussion topic though! > > Conor Flynn wrote: > >> > >> Our field crew is working in the extensive wetlands surrounding Alamosa, > >> CO and we've noticed something interesting: there are no mosquitoes in > or > >> near Alamosa. > >> This is because the city sprays for them regularly. We're not > >> complaining... but we have also noticed fewer grasshoppers, bees, and > frogs > >> than we might otherwise expect. Are these (and other) species directly > >> affected by the insecticide (which chemicals are used post-DDT?) and/or > are > >> mosquitoes ecologically important -- even keystone -- species? What > happens > >> when you remove a parasite from the foodweb? Our field crew is, among > other > >> things, cataloging the vegetation in the area -- could we expect to see > e.g. > >> fewer flowering plants? Anything else we could look for? Is anyone > doing > >> research on this quasi-Silent Spring phenomenon or know more about the > >> possible ramifications of parasite/pest control? > > >
