This week the blogosphere is busy recapping 2007 with lists of top stories in politics, news, and celebrity haircuts. In all the hoopla surrounding year’s end, somehow everyone seems to have forgotten the ants, even though the, um, fast-paced world of Myrmecology has made plenty of discoveries this year. In no particular order, here is my list of the most significant advances in Ant Science from 2007.
Argentine ants and Fire ants- two of the world’s worst invasive species- keep each other in check in their common native range. The perennial mystery of invasive ants is why they are so dominant in their introduced ranges but so benign in their native ranges. LeBrun et al went to the heart of the invasives’ native range, the Paraná river flood plain, and selectively removed nests of either Fire ants or Argentine ants from areas where both naturally occur. In response, the dominance of the other species increased, showing how competition may limit populations of these ants in their native habitat. (Source: LeBrun et al. 2007. An experimental study of competition between fire ants and Argentine ants in their native range.)
- Carpenter ants use gut bacteria to move lower on the food chain. Another perennial ecological mystery about ants has been why there are so many of them. Most terrestrial ecosystems have vast numbers of ants, outweighing the sum total of the much larger vertebrates. The key seems to be that ants can move themselves down the food chain, plugging into the highly-productive primary plant biomass. Feldhaar et al revealed the mechanism behind how Carpenter ants achieve this jump: the gut bacterium Blochmannia is able to make key amino acids available to the ants from otherwise lower-nutrient foods. (Source: Feldhaar et al 2007. Nutritional Upgrading for Omnivorous Carpenter Ants by the Endosymbiont Blochmannia.)
Adult ant traits are partly the result of the care they receive as larvae. In a clever series of cross-fostering experiments between different Temnothorax species, Tim Linksvayer showed that adult size was determined in part by the species charged with raising the larvae. Larger species raised larger ants, even when given larvae of a normally smaller species. Thus, adult worker size in ants is under genetic control, but not in as direct a manner as one might think. Linksvayer’s study is an elegant demonstration of how traits are determined by the interaction of nature and nurture. (Source: Linksvayer, T. A. 2007. Ant Species Differences Determined by Epistasis between Brood and Worker Genomes.)
- The long awaited E. O. Wilson Festschrift was published. This volume commemorates the 50th anniversary of Wilson’s Ph.D. thesis (a taxonomic revision of the North American Lasius) with over two dozen contributions from the world’s ant taxonomists. Among the festschrift’s many treats, we now have keys to Australian Camponotus, North American Army Ants, New World Gnamptogenys and Wasmannia, along with revisions of Meranoplus, Mayriella, Perissomyrmex, and others. We also gained a new ant genus, Dolopomyrmex.
Formica wood ants guard against disease using antibacterial properties of plant resins. Chapuisat et al. experimentally demonstrated a positive effect of plant resins on the survival of both adults and brood. (Source: Chapuisat, M. et al. 2007. Wood ants use resin to protect themselves against pathogens.)
- Traditional notions of Army Ant evolution were partly overturned by a molecular phylogeny of the old world driver ants. Kronauer et al showed that subterrannean foraging, assumed to be the ancestral condition for Dorylus army ants, re-evolved at least once from leaf-litter foraging species. The team also found that key morphological characters were generally more associated with ecological niche than with phylogeny. (Source: Kronauer et al 2007. A molecular phylogeny of Dorylus army ants provides evidence for multiple evolutionary transitions in foraging niche.)
- Ant invasions can be of more complex origin than they first appear. Mikheyev and Mueller showed that the little fire ant Wasmannia auropunctata, a pest worldwide, appears to have originated from at least two different source populations. (Source: Mikheyev and Mueller 2007. Genetic relationships between native and introduced populations of the little fire ant Wasmannia auropunctata.) Similarly Barry Bolton, in a recent revision of Technomyrmex, determined that the White-Footed Ant that is invasive in various regions turns out to be a complex of several related species instead of the singular T. albipes. (Source: Bolton 2007. Taxonomy of the dolichoderine ant genus Technomyrmex Mayr (Hymenoptera: Formicidae) based on the worker cast.)
Ants have memory. At least, the behavior of individual ants is shaped by previous experience. A study by Ravary et al on Cerapachys demonstrated that ants with early successful foraging experience tend to remain as foragers as they age, while those that early on meet with failure turn to other tasks like brood care. (Source: Ravary et al 2007. Individual Experience Alone Can Generate Lasting Division of Labor in Ants.) A different study, conducted by Dreier et al. on two different Pachycondyla species, showed that queens can store information about ants with which they had previously interacted (Source: Dreier et al. 2007. Long-term memory of individual identity in ant queens.)
- Early in the year, the number of described ant species surpassed 12,000. (Source: Antbase.org.) A partial list of these new species can be found here: New taxa of Formicidae described in 2007.
Outside the realm of technical publications, 2007 also saw other advances, especially online. Kiko Gómez & Xavier Espadaler created a fantastic database of Spanish Ants at hormigas.org, Antweb.org continued to add new faunas such as Costa Rica and New Zealand, Ajay Narendra launched a live ant image gallery for the Indian and Australian faunas, Kari Ryder-Wilkie continued to add images to the Ants of Tiputini, Jochen Bihn added more pages to the Ants of Cachoeira, Nugi from the Ant Farm Boards created an image gallery of Indonesian insects, and Benoit Guenard launched ant image galleries from Australia and North Carolina. The Ant Course was held in Arizona this year, attracting over two dozen students, and instructors Brian Fisher and Stefan Cover published an excellent guide to the Ant Genera of North America. American Public Television’s NOVA program produced an ant-related show, and National Geographic continued to publish Mark Moffett’s photographic series on ants.
Here’s hoping that 2008 holds yet more Myrmecological treats!