Relationships between the distributions of nesting ants and flora were investigated in a re-created tallgrass prairie located in northeastern Illinois. One-third of 167 randomly selected 1m2 quadrats in the prairie contained ant nests. Basal coverage of ground by tall grass shoots was greater in quadrats having ant nests than in those lacking ant nests. In addition, clumps of big bluestem (Andropogon gerardii) that were inhabited by the ant, Acanthomyops clavigera, had higher median rank densities than adjacent clumps lacking nests. The clumps also showed a negative correlation between big bluestem shoots/ cm2 and area occupied by the clump at ground level. These significant findings relating to the distribution of nesting ants and tall grasses indicate ants have ecologic importance in re-created prairie that warrants greater scrutiny among restoration scientists

Dave, Dhvani G

Parker, Charise L

Petersen, Chris E

Petersen, Renee E

English

Valparaiso University

The Great Lakes Entomologist Volume 35 Number 1 - Spring/Summer 2002 Number 1 - Spring/Summer 2002 Article 5 April 2002 Ant-Plant Relationships in a Re-Created Tallgrass Prairie Chris E. Petersen College of DuPage Dhvani G. Dave College of DuPage Charise L. Parker College of DuPage Renee E. Petersen College of DuPage Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Petersen, Chris E.; Dave, Dhvani G.; Parker, Charise L.; and Petersen, Renee E. 2002. "Ant-Plant Relationships in a Re-Created Tallgrass Prairie," The Great Lakes Entomologist, vol 35 (1) Available at: https://scholar.valpo.edu/tgle/vol35/iss1/5 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 2002 THE GREAT LAKES ENTOMOLOGIST 27ANT-PLANT RELATIONSHIPS IN A RE-CREATED TALLGRASS PRAIRIEChris E. Petersen1, Dhvani G. Dave1, Charise L. Parker1, and Renee E. Petersen1 ABSTRACTRelationships between the distributions of nesting ants and flora were investigated in a re-created tallgrass prairie located in northeastern Illinois. One-third of 167 randomly selected 1m2 quadrats in the prairie contained ant nests.  Basal coverage of ground by tall grass shoots was greater in quadrats having ant nests than in those lacking ant nests.  In addition, clumps of big bluestem (Andropogon gerardii) that were inhabited by the ant, Acanthomyops clavigera, had higher median rank densities than adjacent clumps lacking nests. The clumps also showed a negative correlation between big bluestem shoots/cm2 and area occupied by the clump at ground level.  These significant findings relating to the distribution of nesting ants and tall grasses indicate ants have ecologic importance in re-created prairie that warrants greater scrutiny among restoration scientists.____________________Ants (Formicidae) have profound effects on most terrestrial systems as soil movers (Baxter and Hole 1967), modifiers of the physical and chemical proper-ties of soil in which they nest (Baxter and Hole 1967, Culver and Beattie 1983, Lesica and Kannowski 1998, Newman and Wolff 1990), consumers (Soule and Knapp 1996), protectors of certain plants and herbivorous insects (Hammond 1995, Huxley 1980), and seed dispersal agents (Handel et al. 1981).  Through these effects, ants influence the composition of and succession within plant communities (Beattie and Culver 1977, Rissing 1986).  Despite their recognized importance in natural systems, the ecological importance of ants in restored systems has received little attention.Restoration offers to conserve biodiversity by the recovery of degraded land through the reintroduction of its former components i.e., species and ecologi-cal processes (Dobson et al. 1997).  Too often, the term “restoration” is used to describe re-creation projects, in which the original substrate has been destroyed and recovery of the natural system must begin anew.  In DuPage County, Illinois, the location of the following study, re-creation projects have offered to preserve biodiversity of tallgrass prairie that once covered much of the county.  Today, only 3.5 hectares of the original 74,000 hectares of tallgrass prairie remains in the county (IDENR 1994), similar to the demise that has occurred throughout the historic range of the ecosystem (Samson and Knopf 1994).  With the amount of remnant prairie being so small, species preservation has undoubtedly been compromised giving significance to re-creation efforts.  However, these efforts have been biased to recovery of tallgrass prairie vegetation.  This is unfortunate as the establishment and successional change of tallgrass prairie vegetation is influenced by other organisms such as ants (Howe 1994, IDENR 1994, Ham-mond 1995, Newman and Wolff 1990).  Over 100 species of ants have been found in tallgrass prairie (Trager 1998). Ants are so abundant in the prairie that they can surpass grasshoppers in total insect biomass.  Their presence in restored and re-created sites is apparent in the form of visual observation of individuals and mounds even within a few  1Natural Sciences Division, College of DuPage, 425 Fawell Blvd., Glen Ellyn, IL 601871Petersen et al.: Ant-Plant Relationships in a Re-Created Tallgrass PrairiePublished by ValpoScholar, 200228 THE GREAT LAKES ENTOMOLOGIST Vol. 35, No. 1years of initial recovery (Petersen et al. 1998, Trager 1990).  The objective of this study was to explore relationships between the distributions of nesting ants and tallgrass prairie flora.  Our study was intended to be preliminary in scope and provide a baseline for more discriminating studies in the future.MATERIALS AND METHODSThe study site was the Russell Kirt Tallgrass Prairie located on the campus of College of DuPage, Illinois.  Re-creation efforts of the 7.5-hectare preserve began in 1984 with seed broadcasting and seedling transplant on top of clay and construction debris deposited from campus construction.  The flora consists of some 150 species that are characteristic of the mesic prairie and wetlands that once covered the area (Swink and Wilhelm 1994).  Grasses most frequently encountered at this site are big bluestem (Andropogon gerardii Vitman), In-dian grass (Sorghastrum nutans (L.) Nash), and prairie dropseed (Sporobolus heterolepis Gray).  Kirt (1989) provides a comprehensive listing of plants found within the preserve that has been burned each spring.From June 14 until July 8, 2001, the area covered by plant shoots at ground level and the presence of ant nests were recorded from each of 137 1-m2 square quadrats taken along randomly selected transects.  Three to five evenly spaced quadrats were sampled along each of the 28 transects that ranged from 10m to 30m in length.  A quadrat was only visited once.  Mann-Whitney tests were used to compare surface coverage of grasses, forbs, and all plants (grasses and forbs) within quadrats having ant nests to those without.  Significant differences (α< 0.05) in median rank contribution were expected where interactions in some form occur between nesting ants and plants growing upon and immediately around the nests.Relationships between plant distribution and nesting ants were also ex-plored with two mound-building species, Acanthomyops clavigera (Roger) and Formica nitidiventris Emery.  The nests of these species were integrated with and inseparable from clumps of big bluestem in which the nests were located. Clumps were distinguished as aggregates of tall grasses separated by at least 20 cm of bare substrate from other clumps.  The clumps of big bluestem inhabited by these ants were distinguished by the added height (up to several centime-ters) and loose texture of the soil as compared to clumps lacking ant nests.  The number of shoots of big bluestem projecting from a clump, and also the area of the clump, were measured in each ant-inhabited clump and the closest clump of big bluestem without ant nests.  It was assumed one shoot emerging from the ground was one individual, although perhaps a genetic clone of others in the clump.  Wilcoxon paired-sample tests were used to compare median ranks of big bluestem counts/cm2 between clumps having nests and those without. Again, significant statistical results were expected where ant-big bluestem in-teractions occur.  Spearman rank correlation was used to test for relationships between clump area and the count of big bluestem shoots/cm2.   Big bluestem is known to self-shade (Jurik and Kliebenstein 2000), leading to the expectation that clump area would be negatively correlated to density.  Our interest was how the presence of ant nests affects the correlation.RESULTSNests of six ant species were found in a third of the 137 quadrats (Table 1). Nests of Lasius alienus (Foerster) were the most common, being either located in close proximity of one another (within centimeters) or possessing multiple entrances spread over several meters.  L. alienus was not found to nest within clumps of vegetation, but only on barren ground.  In contrast, nests of the next most common species, A. clavigera and F. nitidiventris, were found within clumps of big bluestem, Indian grass, and prairie dropseed.  Coverage of ground 2The Great Lakes Entomologist, Vol. 35, No. 1 [2002], Art. 5https://scholar.valpo.edu/tgle/vol35/iss1/52002 THE GREAT LAKES ENTOMOLOGIST 29Table 1.  Percent of 137 quadrats having ants according to species of ant.Nesting species %Ants nests were absent 67.9Acanthomyops clavigera (Roger) 5.1Formica nitidiventris Emery 5.1F. subsericea Say 2.9Lasius alienus (Foerster) 16.8Solenopsis molesta (Say) 1.5Tetramorium caespitum (Linnaeus) 0.7Table 2.  Mean (_x + SD; n) coverage of ground by plants among quadrats having ant nests and quadrats lacking ant nests.  The Z and P values from Mann-Whitney tests indicate degree of significance between quadrat types.  Plant                       Coverage of ground by plants (cm2 plant shoot/cm2 ground)Category Quadrats  Quadrats  Z  P with nests without nestsTallgrass 0.14 + 0.13 (44) 0.11 + 0.12 (93) 2.28 0.02Forbs 0.01 + 0.02 (44) 0.02 + 0.04 (93) 1.12 0.26Tallgrass +Forbs 0.15 + 0.13 (44) 0.13 + 0.12 (93) 1.55 0.12Table 3.  Summary (_x + SD, n) of counts of big bluestem shoots/cm2 and size of clumps (cm2) for clumps having ant nests and adjacent clumps lacking ant nests according to ant species.  The Z and P values from Wilcoxon paired-sample tests indicates degree of significance between clump types.Ant Plant  Clump type Clump typespecies measurement with nest without nest Z PAcanthomyops clavigera Count of big bluestem shoots/cm2 of clump 0.14 + 0.09 (21) 0.10 + 0.08 (21) 2.31 0.02 Size of big bluestem clump (cm2) 325 + 427 (21) 184 + 130 (21) 1.01 0.31Formica nitidiventris Count of big bluestem shoots/cm2 of clump 0.11 + 0.07 (11) 0.10 + 0.06 (11) 0 1 Size of big bluestem clump (cm2) 400 + 281 (11) 177 + 73  (11) 2.52 0.013Petersen et al.: Ant-Plant Relationships in a Re-Created Tallgrass PrairiePublished by ValpoScholar, 200230 THE GREAT LAKES ENTOMOLOGIST Vol. 35, No. 1by these grasses was highest in plants having ant nests (Table 2).  The median rank coverage of forbs which included lead plant (Amorpha canescens Pursh), white and red prairie clover (Dalea candida Michx. ex Willd. and D. purpurea Vent.), rattlesnake master (Eryngium yuccifolium Michx.), and beebalm (Mo-narda fistulosa L.), were not significantly different between quadrats having nests and those without.Big bluestem clumps having nests of A. clavigera had significantly higher median rank counts of shoots/cm2 than clumps lacking nests (Table 3).  No dif-ference in shoot counts/cm2 was observed between clumps having nests of F. nitidiventris and those without.  The area covered by big bluestem clumps tended to be larger when ant nests were present, and was significantly larger where F. nitidiventris nested.  A significant negative relationship between counts of big bluestem shoots/cm2 and clump area was found where A. clavigera nested (Table 4).  In the same type of analysis, but with F. nitidiventris, significance was just missed.  DISCUSSIONAll of the ant species observed in this study are widely distributed in North America and are known from a variety of habitats to include oak and pine forests, pasture, and natural tallgrass prairie (Gregg 1944, Talbot 1934, Trager 1998).  The feeding habits of A. clavigera, F. nitidiventris, F. subsericea Say, and L. alienus include scavenging for dead macroinvertebrates and tend-ing aphids (Burrill and Smith 1919, Greg 1944, Ross et al. 1971, Wheeler and Wheeler 1986).  A. clavigera in particular is inclined to remain subterranean, tending and, at times, consuming root feeding aphids (Trager 1998).  Solenopsis molesta (Say) and Tetramorium caespitum (Linnaeus) are scavengers and seed predators (Ross et al. 1971, Trager 1998).  S. molesta is also known to live within mounds of larger ant species where it feeds on discarded matter and immature stages of host ants.  Greater coverage of ground by tall grasses where ant nests occur and the higher density of big bluestem shoots in clumps having nests of A. clavigera are evidence of a positive relationship between grasses and ants in the 16-year old re-created prairie.  However, it remains unknown whether and how the tall grass or the ant community promotes the other.  Nesting ants may loosen soil, promoting aeration, drainage, and thus tall grass growth.  Seed predation and aphid tending by ant colonies may also function to restrict tall grass competi-tors, allowing greater tall grass growth in clumps.  Alternatively, tall grass may provide food to nesting ants in the form of tissues and exudates via aphids. Growth may be limited in larger clumps of big bluestem due to self-shading and greater attraction of root-feeding aphids, accounting for the negative correlation between clump area and shoot density.Table 4.  Spearman Rank Order Correlation analysis of big bluestem clump area (cm2) and counts of big bluestem shoots/cm2 according to the presence of ant nests.Ant species R T P NAcanthomyops clavigera  Clumps with nest -0.59 3.17 <0.01 21 Clumps without nests -0.29 1.31 0.21 21Formica nitidiventris  Clumps with nests -0.56 2.05 0.07 11 Clumps without nests -0.22 0.66 0.52 114The Great Lakes Entomologist, Vol. 35, No. 1 [2002], Art. 5https://scholar.valpo.edu/tgle/vol35/iss1/52002 THE GREAT LAKES ENTOMOLOGIST 31Clearly, more study is needed to scrutinize these hypotheses, including information about the presence and abundance of root-feeding aphids.  Find-ings of significant relationships between the distribution of nesting ants and tall grasses indicate ants have ecologic importance in re-created prairie that may affect the process and outcome of floral establishment.  Long-term studies should help identify patterns in ant-plant interactions, including the perennial nature of interactions within particular tall grass clumps.  ACKNOWLEDGEMENTSThe research was supported by a Tellabs Grant.  Appreciation is extended to B. Petersen, L. Randa, and J. Sutherland for their valuable comments in preparation of this manuscript.LITERATURE CITEDBaxter, F. P. and F. D. Hole.  1967.  Ant (Formica cinerea) pedoturbation in a prairie soil. Soil Sci. Soc. Amer. Proc. 31:425-428.Beattie, A. J. and D. C. Culver. 1977.  Effects of the mound nests of the ant, Formica obscuripes, on the surrounding vegetation.  Am. Midl. Nat. 97:390-399.Burrill, A. C. and M. R. Smith.  1919.  A key to the species of Wisconsin ants, with notes on their habits.  Ohio J. Sci. 19:279-292.Culver, D. C. and A. J. Beattie.  1983.  Effects of ant mounds on soil chemistry and vegeta-tion patterns in a Colorado montane meadow.  Ecology 64:485-492.Dobson, A. P., A. D. Bradshaw, and A. J. M. Baker.  1997.  Hopes for the future: restora-tion ecology and conservation biology.  Science 277:515-522.Gregg, R. E. 1944.  The ants of the Chicago region.  Ann. Entomol. Soc. Amer. 37:447-480.Hammond, P. C. 1995.  Conservation of biodiversity in native prairie communities in the United States.  J. Kansas Entomol. Soc. 68:1-6.Handel, S. N., S. B. Fisch, and G. E. Schatz. 1981.  Ants disperse a majority of herbs in a mesic forest community in New York State.  Bull. Torrey Bot. Club 108:430-437. Howe, H. F.  1994.  Managing species diversity in tallgrass prairie:  Assumptions and implications.  Cons. Biol. 8:691-704.Huxley, C. R. 1980.  Symbiosis between ants and epiphytes.  Biol. Rev. (Camb.) 55:321-340. Illinois Department of Energy and Natural Resources (IDENR). 1994.  The Changing Illinois Environment: Critical Trends Technical Report of the Critical Trends Assessment Project Volume 3: Ecological Resources.  IDENR, Springfield, IL.Jurik, T. W. and H. Kliebenstein.  2000.  Canopy architecture, light extinction and self-shading of a prairie grass, Andropogon gerardii.  Am. Midl. Nat. 144:51-65.Kirt, R. R.  1989.  Prairie Plants of Northern Illinois: Identification and Ecology.  Stipes Publishing Company, Champaign, IL.Lesica, P. and P. B. Kannowski. 1998.  Ants create hummocks and alter structure and vegetation of a Montana fen.  Amer. Midl. Nat. 139:58-68.Newman, L. M. and R. J. Wolff. 1990.  Ants of a northern Illinois savanna and degraded avanna woodland, pp. 71-73.  In:  D. D. Smith and C. A Jacobs (ed.), Proceedings of the Twelfth North America Prairie Conference.  University of Northern Iowa, Cedar Rapids, IO.Petersen, C. E., K. Zwolfer, and J. Fradkin.  1998.  Ant fauna of reconstructed tallgrass Prairie in northeastern Illinois.  Trans. Ill. State Acad. Sci. 91:85-90.Rissing, S. W.  1986.  Indirect effects of granivory by harvester ants: plants species com-position and reproductive increase near ant nests.  Oecologia 68:231-234.5Petersen et al.: Ant-Plant Relationships in a Re-Created Tallgrass PrairiePublished by ValpoScholar, 200232 THE GREAT LAKES ENTOMOLOGIST Vol. 35, No. 1Ross, H. H. , G. L. Rotramel, and W. E. LaBerge.  1971.  A synopsis of common and economic Illinois ants, with keys to the genera (Hymenoptera: Formicidae). Illinois Nat. Hist. Surv. Bull. 71:1-22.Samson, F. and F. Knopf.  1994.  Prairie conservation in North America.  BioScience 44: 418-421.Soule, P. T. and P. A. Knapp.  1996.  The influence of vegetation removal by Western Har-vester ants (Pogonomyrmex osyheei) in a relict area of sagebrush-steppe in Central Oregon.  Am. Midl. Nat. 136:336-345.Swink, R. and G. Wilhelm.  1994.  Plants of the Chicago Region, 4th ed.  The Morton Arboretum, Lisle, IL.Talbot, M.  1934.  Distribution of ant species in the Chicago region with reference to ecological factors and physiological toleration.  Ecology 15:416-439.Trager, J. C.  1990.  Restored prairies colonized by native prairie ants (Missouri, Illinois). Restoration and Management Notes 8:104-105.Trager, J. C.  1998.  An introduction to ants (Formicidae) of the tallgrass prairie. Missouri Prairie Journal 18:4-8.Wheeler, G. and J. Wheeler.  1986.  The ants of Nevada. Nat. Hist. Mus. Los Angeles, CA.6The Great Lakes Entomologist, Vol. 35, No. 1 [2002], Art. 5https://scholar.valpo.edu/tgle/vol35/iss1/5

Ant-Plant Relationships in a Re-Created Tallgrass Prairie

ValpoScholar

The Great Lakes Entomologist 
Volume 35 
Number 1 - Spring/Summer 2002 Number 1 - 
Spring/Summer 2002 
Article 5 
April 2002 
Ant-Plant Relationships in a Re-Created Tallgrass Prairie 
Chris E. Petersen 
College of DuPage 
Dhvani G. Dave 
College of DuPage 
Charise L. Parker 
College of DuPage 
Renee E. Petersen 
College of DuPage 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Petersen, Chris E.; Dave, Dhvani G.; Parker, Charise L.; and Petersen, Renee E. 2002. "Ant-Plant 
Relationships in a Re-Created Tallgrass Prairie," The Great Lakes Entomologist, vol 35 (1) 
Available at: https://scholar.valpo.edu/tgle/vol35/iss1/5 
This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. 
It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. 
For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 
2002 THE GREAT LAKES ENTOMOLOGIST 27
ANT-PLANT RELATIONSHIPS IN A RE-CREATED TALLGRASS 
PRAIRIE
Chris E. Petersen1, Dhvani G. Dave1, Charise L. Parker1, and 
Renee E. Petersen1 
ABSTRACT
Relationships between the distributions of nesting ants and flora were 
investigated in a re-created tallgrass prairie located in northeastern Illinois. 
One-third of 167 randomly selected 1m2 quadrats in the prairie contained ant 
nests.  Basal coverage of ground by tall grass shoots was greater in quadrats 
having ant nests than in those lacking ant nests.  In addition, clumps of big 
bluestem (Andropogon gerardii) that were inhabited by the ant, Acanthomyops 
clavigera, had higher median rank densities than adjacent clumps lacking nests. 
The clumps also showed a negative correlation between big bluestem shoots/
cm2 and area occupied by the clump at ground level.  These significant findings 
relating to the distribution of nesting ants and tall grasses indicate ants have 
ecologic importance in re-created prairie that warrants greater scrutiny among 
restoration scientists.
____________________
Ants (Formicidae) have profound effects on most terrestrial systems as soil 
movers (Baxter and Hole 1967), modifiers of the physical and chemical proper-
ties of soil in which they nest (Baxter and Hole 1967, Culver and Beattie 1983, 
Lesica and Kannowski 1998, Newman and Wolff 1990), consumers (Soule and 
Knapp 1996), protectors of certain plants and herbivorous insects (Hammond 
1995, Huxley 1980), and seed dispersal agents (Handel et al. 1981).  Through 
these effects, ants influence the composition of and succession within plant 
communities (Beattie and Culver 1977, Rissing 1986).  Despite their recognized 
importance in natural systems, the ecological importance of ants in restored 
systems has received little attention.
Restoration offers to conserve biodiversity by the recovery of degraded land 
through the reintroduction of its former components i.e., species and ecologi-
cal processes (Dobson et al. 1997).  Too often, the term “restoration” is used to 
describe re-creation projects, in which the original substrate has been destroyed 
and recovery of the natural system must begin anew.  In DuPage County, Illinois, 
the location of the following study, re-creation projects have offered to preserve 
biodiversity of tallgrass prairie that once covered much of the county.  Today, 
only 3.5 hectares of the original 74,000 hectares of tallgrass prairie remains in 
the county (IDENR 1994), similar to the demise that has occurred throughout 
the historic range of the ecosystem (Samson and Knopf 1994).  With the amount 
of remnant prairie being so small, species preservation has undoubtedly been 
compromised giving significance to re-creation efforts.  However, these efforts 
have been biased to recovery of tallgrass prairie vegetation.  This is unfortunate 
as the establishment and successional change of tallgrass prairie vegetation is 
influenced by other organisms such as ants (Howe 1994, IDENR 1994, Ham-
mond 1995, Newman and Wolff 1990).  
Over 100 species of ants have been found in tallgrass prairie (Trager 1998). 
Ants are so abundant in the prairie that they can surpass grasshoppers in total 
insect biomass.  Their presence in restored and re-created sites is apparent in 
the form of visual observation of individuals and mounds even within a few 
 1Natural Sciences Division, College of DuPage, 425 Fawell Blvd., Glen Ellyn, IL 60187
1
Petersen et al.: Ant-Plant Relationships in a Re-Created Tallgrass Prairie
Published by ValpoScholar, 2002
28 THE GREAT LAKES ENTOMOLOGIST Vol. 35, No. 1
years of initial recovery (Petersen et al. 1998, Trager 1990).  The objective of 
this study was to explore relationships between the distributions of nesting ants 
and tallgrass prairie flora.  Our study was intended to be preliminary in scope 
and provide a baseline for more discriminating studies in the future.
MATERIALS AND METHODS
The study site was the Russell Kirt Tallgrass Prairie located on the campus 
of College of DuPage, Illinois.  Re-creation efforts of the 7.5-hectare preserve 
began in 1984 with seed broadcasting and seedling transplant on top of clay 
and construction debris deposited from campus construction.  The flora consists 
of some 150 species that are characteristic of the mesic prairie and wetlands 
that once covered the area (Swink and Wilhelm 1994).  Grasses most frequently 
encountered at this site are big bluestem (Andropogon gerardii Vitman), In-
dian grass (Sorghastrum nutans (L.) Nash), and prairie dropseed (Sporobolus 
heterolepis Gray).  Kirt (1989) provides a comprehensive listing of plants found 
within the preserve that has been burned each spring.
From June 14 until July 8, 2001, the area covered by plant shoots at ground 
level and the presence of ant nests were recorded from each of 137 1-m2 square 
quadrats taken along randomly selected transects.  Three to five evenly spaced 
quadrats were sampled along each of the 28 transects that ranged from 10m to 
30m in length.  A quadrat was only visited once.  Mann-Whitney tests were used 
to compare surface coverage of grasses, forbs, and all plants (grasses and forbs) 
within quadrats having ant nests to those without.  Significant differences (α< 
0.05) in median rank contribution were expected where interactions in some 
form occur between nesting ants and plants growing upon and immediately 
around the nests.
Relationships between plant distribution and nesting ants were also ex-
plored with two mound-building species, Acanthomyops clavigera (Roger) and 
Formica nitidiventris Emery.  The nests of these species were integrated with 
and inseparable from clumps of big bluestem in which the nests were located. 
Clumps were distinguished as aggregates of tall grasses separated by at least 20 
cm of bare substrate from other clumps.  The clumps of big bluestem inhabited 
by these ants were distinguished by the added height (up to several centime-
ters) and loose texture of the soil as compared to clumps lacking ant nests.  The 
number of shoots of big bluestem projecting from a clump, and also the area of 
the clump, were measured in each ant-inhabited clump and the closest clump 
of big bluestem without ant nests.  It was assumed one shoot emerging from 
the ground was one individual, although perhaps a genetic clone of others in 
the clump.  Wilcoxon paired-sample tests were used to compare median ranks 
of big bluestem counts/cm2 between clumps having nests and those without. 
Again, significant statistical results were expected where ant-big bluestem in-
teractions occur.  Spearman rank correlation was used to test for relationships 
between clump area and the count of big bluestem shoots/cm2.   Big bluestem is 
known to self-shade (Jurik and Kliebenstein 2000), leading to the expectation 
that clump area would be negatively correlated to density.  Our interest was 
how the presence of ant nests affects the correlation.
RESULTS
Nests of six ant species were found in a third of the 137 quadrats (Table 1). 
Nests of Lasius alienus (Foerster) were the most common, being either located 
in close proximity of one another (within centimeters) or possessing multiple 
entrances spread over several meters.  L. alienus was not found to nest within 
clumps of vegetation, but only on barren ground.  In contrast, nests of the next 
most common species, A. clavigera and F. nitidiventris, were found within 
clumps of big bluestem, Indian grass, and prairie dropseed.  Coverage of ground 
2
The Great Lakes Entomologist, Vol. 35, No. 1 [2002], Art. 5
https://scholar.valpo.edu/tgle/vol35/iss1/5
2002 THE GREAT LAKES ENTOMOLOGIST 29
Table 1.  Percent of 137 quadrats having ants according to species of ant.
Nesting species %
Ants nests were absent 67.9
Acanthomyops clavigera (Roger) 5.1
Formica nitidiventris Emery 5.1
F. subsericea Say 2.9
Lasius alienus (Foerster) 16.8
Solenopsis molesta (Say) 1.5
Tetramorium caespitum (Linnaeus) 0.7
Table 2.  Mean (_x + SD; n) coverage of ground by plants among quadrats having ant 
nests and quadrats lacking ant nests.  The Z and P values from Mann-Whitney tests 
indicate degree of significance between quadrat types.  
Plant                       Coverage of ground by plants (cm2 plant shoot/cm2 ground)
Category Quadrats  Quadrats  Z  P
 with nests without nests
Tallgrass 0.14 + 0.13 (44) 0.11 + 0.12 (93) 2.28 0.02
Forbs 0.01 + 0.02 (44) 0.02 + 0.04 (93) 1.12 0.26
Tallgrass +
Forbs 0.15 + 0.13 (44) 0.13 + 0.12 (93) 1.55 0.12
Table 3.  Summary (_x + SD, n) of counts of big bluestem shoots/cm2 and size of clumps 
(cm2) for clumps having ant nests and adjacent clumps lacking ant nests according to 
ant species.  The Z and P values from Wilcoxon paired-sample tests indicates degree of 
significance between clump types.
Ant Plant  Clump type Clump type
species measurement with nest without nest Z P
Acanthomyops clavigera
 Count of big bluestem
 shoots/cm2 of clump 0.14 + 0.09 (21) 0.10 + 0.08 (21) 2.31 0.02
 Size of big bluestem
 clump (cm2) 325 + 427 (21) 184 + 130 (21) 1.01 0.31
Formica nitidiventris
 Count of big bluestem
 shoots/cm2 of clump 0.11 + 0.07 (11) 0.10 + 0.06 (11) 0 1
 Size of big bluestem
 clump (cm2) 400 + 281 (11) 177 + 73  (11) 2.52 0.01
3
Petersen et al.: Ant-Plant Relationships in a Re-Created Tallgrass Prairie
Published by ValpoScholar, 2002
30 THE GREAT LAKES ENTOMOLOGIST Vol. 35, No. 1
by these grasses was highest in plants having ant nests (Table 2).  The median 
rank coverage of forbs which included lead plant (Amorpha canescens Pursh), 
white and red prairie clover (Dalea candida Michx. ex Willd. and D. purpurea 
Vent.), rattlesnake master (Eryngium yuccifolium Michx.), and beebalm (Mo-
narda fistulosa L.), were not significantly different between quadrats having 
nests and those without.
Big bluestem clumps having nests of A. clavigera had significantly higher 
median rank counts of shoots/cm2 than clumps lacking nests (Table 3).  No dif-
ference in shoot counts/cm2 was observed between clumps having nests of F. 
nitidiventris and those without.  The area covered by big bluestem clumps tended 
to be larger when ant nests were present, and was significantly larger where 
F. nitidiventris nested.  A significant negative relationship between counts of 
big bluestem shoots/cm2 and clump area was found where A. clavigera nested 
(Table 4).  In the same type of analysis, but with F. nitidiventris, significance 
was just missed.  
DISCUSSION
All of the ant species observed in this study are widely distributed in 
North America and are known from a variety of habitats to include oak and 
pine forests, pasture, and natural tallgrass prairie (Gregg 1944, Talbot 1934, 
Trager 1998).  The feeding habits of A. clavigera, F. nitidiventris, F. subsericea 
Say, and L. alienus include scavenging for dead macroinvertebrates and tend-
ing aphids (Burrill and Smith 1919, Greg 1944, Ross et al. 1971, Wheeler and 
Wheeler 1986).  A. clavigera in particular is inclined to remain subterranean, 
tending and, at times, consuming root feeding aphids (Trager 1998).  Solenopsis 
molesta (Say) and Tetramorium caespitum (Linnaeus) are scavengers and seed 
predators (Ross et al. 1971, Trager 1998).  S. molesta is also known to live within 
mounds of larger ant species where it feeds on discarded matter and immature 
stages of host ants.  
Greater coverage of ground by tall grasses where ant nests occur and the 
higher density of big bluestem shoots in clumps having nests of A. clavigera 
are evidence of a positive relationship between grasses and ants in the 16-year 
old re-created prairie.  However, it remains unknown whether and how the tall 
grass or the ant community promotes the other.  Nesting ants may loosen soil, 
promoting aeration, drainage, and thus tall grass growth.  Seed predation and 
aphid tending by ant colonies may also function to restrict tall grass competi-
tors, allowing greater tall grass growth in clumps.  Alternatively, tall grass may 
provide food to nesting ants in the form of tissues and exudates via aphids. 
Growth may be limited in larger clumps of big bluestem due to self-shading and 
greater attraction of root-feeding aphids, accounting for the negative correlation 
between clump area and shoot density.
Table 4.  Spearman Rank Order Correlation analysis of big bluestem clump area (cm2) 
and counts of big bluestem shoots/cm2 according to the presence of ant nests.
Ant species R T P N
Acanthomyops clavigera 
 Clumps with nest -0.59 3.17 <0.01 21
 Clumps without nests -0.29 1.31 0.21 21
Formica nitidiventris 
 Clumps with nests -0.56 2.05 0.07 11
 Clumps without nests -0.22 0.66 0.52 11
4
The Great Lakes Entomologist, Vol. 35, No. 1 [2002], Art. 5
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2002 THE GREAT LAKES ENTOMOLOGIST 31
Clearly, more study is needed to scrutinize these hypotheses, including 
information about the presence and abundance of root-feeding aphids.  Find-
ings of significant relationships between the distribution of nesting ants and 
tall grasses indicate ants have ecologic importance in re-created prairie that 
may affect the process and outcome of floral establishment.  Long-term studies 
should help identify patterns in ant-plant interactions, including the perennial 
nature of interactions within particular tall grass clumps.  
ACKNOWLEDGEMENTS
The research was supported by a Tellabs Grant.  Appreciation is extended 
to B. Petersen, L. Randa, and J. Sutherland for their valuable comments in 
preparation of this manuscript.
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Ant-Plant Relationships in a Re-Created Tallgrass Prairie

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