Department of Evolution, Ecology & Organismal Biology
Aronoff Laboratory, 318 West 12th Avenue, Columbus, OH 43210
tel: (614) 292-5472 fax: (614) 292-2030
Web production (design, most text, images): Christine Johnson. Questions or comments? Let me know.
To cite these pages: Herbers, J. M. & C. A. Johnson, 2004. http://www.biosci.ohio-state.edu/~herbers/[specific_page].htm [date page accessed or retrieved]
My laboratory
studies insect ecology, behavior, and genetics. Students have
worked on foraging behavior, sex ratio evolution, sociogenetics,
and coevolution. The major projects currently underway focus on
the behavioral ecology and coevolution of slave-making ants. We
are studying several species of these highly-specialized insects
that parasitize the social organization of other species. In
eastern North America, the slavemaking ant Protomognathus americanus enslaves three host species of Temnothorax
(formerly Leptothorax) ants. Comparative studies of
the interactions in three geographic locations show clearly that
the impact of the social parasite on its hosts varies
tremendously in time and space. Frequency of raiding,
destructiveness of slave raids, and aggression by hosts varies
strongly, leading to different coevolutionary dynamics in
different sites. We are just starting parallel studies on how the
slavemaker Temnothorax duloticus affects its host T.
curvispinosus.
A second project focuses on how two different slavemakers in western North American interact with a common host. Both Polyergus breviceps and Formica sanguinea are ants that parasitize the same ant host, Formica argentea. The Polyergus slavemakers are distantly related to their hosts and have evolved to become prudent parasites relative to the Formica slavemaker that is closely related to its host. By studying behavioral interactions and genetic consequences of raiding activity, we can estimate the strength of selection exerted by the slavemakers on their hosts, as well as the reverse. Thus these systems are excellent models for examining how interactions between parasites and hosts co-evolve. Joan Herbers
Current Research Projects at The Ohio State University - Evolution, Ecology & Organismal Biology
Ecology of slave-making ants
Obligate socially-parasitic ant species are incapable of surviving without the social behaviors of another ant species. The slave-maker, or dulotic, ant species are typically specialized for raiding nests of host species for their brood. Pupae and sometimes larvae are brought back to the natal nest, where they mature and become contributing members of the slave-maker colony, laboring on behalf of the slave-makers. Social parasites have long intrigued layman and biologists alike, primarily because of the imposed servitude of another species and the mechanisms that allow for such exploitation to occur. The population dynamics of host and social parasite furthermore offer evolutionary biologists insight into coevolutionary processes.
Our laboratory is currently researching the ecology two species of slave-makers that occur in Ohio, around the greater Columbus area. With the help of John O'Meara, Executive Director of Metro Parks, and OSU alumnus Jon Kraus, our collecting forays into several of the Metro Parks and Kraus Woods Reserve have resulted in the finding of both Temnothorax duloticus and Protomognathus (=Harpagoxenus) americanus slave-makers and their primary host species in the region, Temnothorax curvispinosus. These three species are just a few of the ant species nesting in second-year, hollowed acorn and hickory nuts and twigs that have been inhabited previously by various species of beetle larvae. Using behavioral observation, colony mapping, and microsatellite DNA analysis, we hope to ascertain the relative impact of the two slave-makers on the host population when they occur in sympatry vs in allopatry. Examination of host colony social structure in parasitized and unparasitized populations may aid us in identifying tactics to counter colony decimation by slave raiders. More. Christine Johnson
Classification: Formicidae: Myrmicinae: Formicoxenini: Temnothorax (formerly Leptothorax), Protomognathus (=Harpagoxenus)
A rare inquiline, Temnothorax minutissimus
Upon returning from our collecting trips, we open fully the ant-bearing acorns and hickories we've collected and brush the inhabitants into Fluon-coated nest boxes. Once the ants have settled into the glass slide nests we've provided, we count the number of workers, queens, winged reproductives, and pupae often with the aid of dissecting scope as they are quite small and difficult to see with the naked eye. We can alsodetermine whether we've collected T. duloticus. On one occassion, however, our microscopic examination yielded an unexpected surprise. We not only found at least two species of ants in the nest, but multiple queens of both species a rather uncommon occurrence in ants. By watching the behavior and getting a positive identification by Stefan Cover in the Department of Entomology at the Museum of Comparative Zoology, we discovered we had collected the inquiline, Temnothorax minutissimus.This relatively little known species is a parasite of T. curvispinosus that produces only reproductive females (queens) and every so often males. Apparently, only the dominant parasite queen lays eggs and typically is the individual 'riding' or flanking the sides of the host queen, licking her head. We collected two colonies, a small one containing about 14 T. minutissimus queens and 1 live host queen (there was an abdomen of another) and a large one with about 32 T. minutissimus queens. In the larger nest there are about 8 host queens, but not all of them are flanked by the parasite. Only one or two queens are harassed and usually by two T. minutissimus queens. We've dissected a few of the T. minutissimus to determine whether all are mated and if perhaps more than one is laying eggs. With our very small sample size, it seems that more than just one is mated, but it is yet unclear whether more than one individual is laying eggs. Christine Johnson
Classification: Formicidae: Myrmicinae: Formicoxenini: Temnothorax
The stealth predator Smithistruma*
Although Smithistruma ants may be found on every continent in the world, encounters with Smithistruma are often infrequent due to the small size of the ant - between 2 to 4 mm in length, its relatively slow and innocuous movement, its somewhat cryptic coloration and its often well-concealed nesting sites. Many Smithistruma species are predators of small arthropods such as Collembola (Dejean 1982). Other species apparently exploit nectar and aphid honeydew secretions (Dejean 1991). An interesting characteristic of Smithstruma (and the closely related Strumigenys) is the hardened spongiform growth that appears to ooze from the petiole and post-petiole. Dejan (1985) suggests that this structure may contain an allomone that attracts Collembola to foraging Smithistruma.
Little is known about Smithistruma social structure, although there is often more than one dealate queen within most nests. In our laboratory, we are beginning an examination into the social structure of a local species of Smithistruma collected from hickories. Christine Johnson
Classification: Myrmicinae: Dacetini: Strumigeniti, Smithistruma*
Citations:
Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). Journal of Natural History 33: 1639-1689.
Dejean, A. 1982. Etude éco-éthologique de la prédation chez les fourmis du genre Smithistruma I. Effect du milieu sur le choix de proies chez Smithistruma truncatidens Brown. Insect Science Application 3: 245-249.
Dejean, A. 1985. Etude éco-éthologique de la prédation chez les fourmis du genre Smithistruma II. Attraction des proises principales (Collemboles). Insectes Sociaux, Paris 32: 158-172.
Dejean, A. 1991. Gathering of nectar and exploitation of Aphidadae by Smithistruma emarginata. Biotropica 23: 207-208.
On the web:
Pyramica of Autstralia http://www.ento.csiro.au/science/ants/myrmicinae/pyramica/pyramica_tax_cat.htm
Smithistruma of Costa Rica http://www.evergreen.edu/ants/genera/pyramica/old.genera/smithistruma/Smithistruma.html#Key
Smithistruma of Japan http://taxa.soken.ac.jp/ANT.WWW/Taxo_E/F424--.html
*Note: Pyramica Roger was recently made the senior synonym of Smithisitruma and 16 other Dacetonine genera (Bolton 1999). They have not yet been changed here.
Past Research Projects
Web production (design, text, photos): Christine Johnson. Updated November 8, 2005