Stephanie Johnson Poster

Cyphomyrmex longiscapus one fungus-growing ant species or many?

Abstract

Found commonly on the banks of small streams in the wet forests of Panama, Colombia, and Costa Rica, Cyphomyrmex longiscapus sensu lato is an ideal organism for the study of the evolution of fungus-growing behavior and cultivar specificity.

Morphometrics, nest size and architecture, and other evidence suggest that C. longiscapus s. l. may actually be a complex of several cryptic species that are new to science. C. longiscapus s. l. specimens were collected from three disjunct localities: (i) La Selva Biological Station in Costa Rica, (ii) Bocas del Toro, Panama, and (iii) Darien, Panama. A sample of specimens from each locality were mounted on pins, and a subset of the pinned specimens was selected for measurement; sampling included as many nests as possible in order to eliminate any nest bias.

Three standard ant measurements, head width, head length, and Weber’s length, were taken for 33 ants from Bocas Del Toro, 24 ants from La Selva, and 41 ants from Darien. Specimens representing all three ant castes (workers, reproductive females, and males), were measured digitally using a Leica M40 microscope tethered to a JVC digital camera driven by Automontage software.

The resulting data were analyzed and compared to those produced by a previous study of the Colombian C. longiscapus type series and C. longiscapus ants from central Panama using ANOVA tests and general linear modeling with SYSTAT software. Field observations suggest that the nest architecture of the Costa Rican and Bocas del Toro populations are very different from that of the central Panamanian C. longiscapus populations. The number of workers per nest also differs greatly between typical central Panamanian C. longiscapus populations, which average approximately 20 workers per nest, and the Bocas del Toro population, which averages hundreds of workers per nest. My morphometric analysis indicates that there are significant differences in head width and Weber’s length between the different populations. The combined evidence suggests that the populations studied may actually be different cryptic species; however, additional morphological study and genetic analysis are needed before any firm conclusions can be made.

Introduction

Cyphomyrmex longiscapus nests can be found on steep clay embankments of small streams in Panama and are easily recognized by their characteristic, ear shaped funnel entrances.

Two kinds of fungus gardens are encountered in different species of the genus Cyphomyrmex: (i) mycelium fungus and (ii) “yeast”. Cyphomyrmex longiscapus, which cultivates mycelium gardens, may occupy an important position in the evolutionary transition from mycelium to yeast cultivation.

The purpose of this project is to examine ant putative C. longiscapus from populations collected in Bocas del Toro and Darien, Panama, and in Costa Rica to determine if these ants actually belong to the species or if they are cryptic species new to science. The fungus cultivated by each population is also being studied because other Cyphomyrmex species exclusively grow only a single fungal strain.

Methods

Ants from all three castes, workers, reproductive females (queens), and males, were measured digitally using a Leica M40 microscope tethered to a JVC digital camera driven by Automontage software.

A total of eight measurements were taken on each of the ants to help characterize their body shape and size: (A). head length and head width (B). antennal scape length (C). eye width (D). Weber’s length (E). femur length (F). length and width of post petiole

Measurements were compared with data from a previous study of C. longiscapus from central Panama and the Columbia type series. Data were analyzed with ANOVA tests and general linear modeling.

Results and Discussion

Field observations have suggested that the nest architecture of the Costa Rican and Bocas del Toro ants are very different from that of C. longiscapus nests found in central Panama.

The number of workers per nest differs greatly between central Panamanian C. longiscapus nests, which average approximately 20 workers, and the nests from Bocas del Toro, which contain hundreds of workers.

Morphometric analysis of the head width, head length, and Weber’s length data for all three castes showed significant differences between the populations. In general, the ants from the Colombian type series and those from Costa Rica are larger than the other ants in all measurements and are similar to each other in size. The ants from Bocas del Toro are smaller than those from Colombia and Costa Rica, but are larger than those from Central Panama and the Darien. The ants from Central Panama and the Darien are not significantly different in size at the 95% confidence level.

Conclusions

The differences in nest architecture and colony size, combined with the significant differences in head width, head length, and Weber’s length between the populations, suggests that the populations studied may actually represent three different, cryptic species. However, additional morphological study as well as genetic analyses are needed before any strong conclusions can be drawn.

Acknowledgements

Ted R. Schultz, Ulrich G Mueller, Anna Himler, Eugenia Okonski This research was supported National Science Foundation Research Experiences for Undergraduates program, Award Number DBI-0243512

Works cited

Schultz, T. R., S. A. Solomon, U. G. Mueller, P. Villesen, J. J. Boomsma, R. M. M. Adama, and B. Norden. 2002. Cryptic speciation in the fungus-growing ants Cyphomyrmex longiscapus Weber and Cyphomyrmex muelleri Schultz and Solomon, new species (Formicidae, Attini). Insectes soc.: 331-343.

Synoptics. 2003. Auto-montage, version 4.03.0022 BETA. Frederick, Maryland. Synoptics Ltd.

Systat Software Inc. 2002. SYSTAT, version 10.2.01. Richmond, CA. SYSTAT Software Inc.

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The information presented here represents preliminary research as the result of ten-weeks of investigation in-residence at the National Museum of Natural History. This is not an official publication of the information.

As preliminary information, results and/or findings should not be cited as part of conclusive work. Please contact the authors first if you wish to utilize the information presented here.


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Research Training Program VIRTUAL POSTER SESSION 2003

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2003