Data from: "Divergent evolution of colony-level metabolic scaling in ants"
Summary
This dataset was assembled from the literature to investigate the interspecific scaling of whole-colony metabolic rate in ants relative to ecological and social traits. Metabolic rates of active ant colonies and their masses were obtained from published data compilations (Shik et al., 2012, 2014), references therein and studies citing those references in Google Schoolar. Then, data on trophic level, foraging coordination level, and caste polymorphism of those species were searched for in published data compilations on those traits (see below). Only species for which all analyzed variables were available were used. Only one study not included in the compilations met this criterion (Mason et al., 2015). Data provided in the compilations were compared to those in the original studies to guarantee they were correct. The combined dataset comprised 53 ant species in 7 subfamilies, sampled by 9 studies across 10 sites in five countries (Belgium, Panama, South Africa, United States, and Venezuela). Variables were species means, with one to 25 colonies sampled per species.
This dataset is composed of three files: "Data_ant_data.csv" contains comparative data on 26 variables for 53 ant species; "Data_ant_tree.txt" is a phylogenetic tree for the studied ant species; and "Data_R_script_UPDATED.R" is an R script to reproduce the original analysis and plots.
Data assembly
Metabolic rate was estimated from CO2 produced in respirometry chambers, but method details varied. For most species, colonies were collected in the field, had their natural composition, and were measured using flow-through respirometry. For some species, colonies were reared from queens for one year in the laboratory, had their composition set to an adult:brood ratio of 4:1, and/or were measured using closed-system respirometry. All colonies had food ad libitum before metabolic measurements, but colony maintenance conditions varied. For a few species, the largest colonies were too large for the respirometry chamber, so colonies were fragmented into two or three subcolonies, which were averaged to represent the species. All colonies were considered active, based on direct observation reported by some of the original studies and on the fact that, where measured, whole colonies tend to have higher mass-specific metabolic rate than isolated worker groups. Most colony metabolic rates were provided at 25ºC, but some were provided at 30ºC. Accordingly, all values were standardized to 25 °C assuming Q10 = 2.00. All metabolic measurements were expressed in Watts. Seven species were fungus-farmers, but colony metabolic rate and mass could be separated from that of fungi for only five of these.
Colonies used for respirometry were weighed to determine their mass. Wet mass was reported for most species, but only dry mass was reported for some. Because we were interested in living colonies, we considered the former. We used species for which both measurements were available to regress wet colony mass (Y) on dry colony mass (X) (both log10-transformed) and then predicted wet colony mass for those species for which only dry mass was reported (n = 27, log10Y = -2.80 + 1.22 log10X, r² = 0.99, P < 0.001).
Trophic level was obtained from a global data compilation including 592 species (Drager et al. 2023). The average trophic level of ant species was estimated from nitrogen stable isotope ratios by assuming trophic level increases with the difference between the ratios of the focal ant and of a baseline (a co-occurring primary producer). Direct estimates of trophic level were available for 13 of the analyzed species, so we used genera means for the remaining species. This assumes that congeneric species tend to have similar trophic levels, which is supported by the significant phylogenetic signal of this trait (Pagel’s λ = 0.74; Drager et al. 2023). For Nylanderia guatemanlensis, the mean trophic level of its former genus (Paratrechina) was used, as there was no data for Nylanderia.
Foraging coordination level was assigned based on published data compilations on ant foraging strategies, covering over 400 species (Beckers et al. 1989, Lanan 2014). For the analyzed species, the following levels can be recognized: (1) solitary foraging: foragers search for food and collect it individually; (2) tandem running: a forager that returns to the nest after successfully finding a resource guides a single nestmate to that resource; (3) group recruitment: returning foragers guide groups of nestmates to detected resources; (4) mass recruitment: returning foragers lay short-lived pheromone trails from the food to the nest, which then guide nestmates to the food; (5) trunk trails: long-lived trails are laid between stable food sources and the nest that both guide foragers and serve as starting points for new trails. Hence, foraging complexity was coded as an ordinal variable: solitary foraging (1), tandem running (2), group recruitment (3), mass recruitment (4), and trunk trail (5).
Caste polymorphism was assigned based on a global data compilation of 8890 species (La Richelière et al., 2022). These authors classified each species as either polymorphic (1) or monomorphic (0), defining polymorphism as any interindividual variation in size or head-to-body allometry reported in the primary literature, either continuous or discrete variation. Species for which there were no published data were assigned the same category as congeneric species (La Richelière et al., 2022). Here, 47 species could have their polymorphism directly assigned from the compilation. For the remaining six species (Brachymyrmex sp., Crematogaster sp., Leptothorax unifasciatus, and three unidentified Solenopsis spp.), we obtained the means of their respective genera as an estimate of the probability of being polymorphic given the known proportion of polymorphism in the genus. Species in genera where this probability was larger than 0.5 were classified as polymorphic (1), and monomorphic otherwise (0).
Phylogenetic relationships among the analyzed species were manually coded in Newick format using a genus-level tree as reference (AntWiki, 2024)(Supporting Information, Figure S2). Within-genus relationships were represented as polytomies, and branch lengths were standardized to the same value (one). Species names were checked for validity and updated as required according to an on-line database(AntWiki, 2024).
References
AntWiki. (2024). Phylogeny of Formicidae. Available at: https://www.antwiki.org/wiki/Phylogeny_of_Formicidae
Beckers, R., Goss, S., Deneubourg, J. L., & Pasteels, J. M. (1989). Colony size, communication and ant foraging strategy. Psyche, 96, 239–256.
Drager, K. I., Rivera, M. D., Gibson, J. C., Ruzi, S. A., Hanisch, P. E., Achury, R., & Suarez, A. V. (2023). Testing the predictive value of functional traits in diverse ant communities. Ecology and Evolution, 13(4). https://doi.org/10.1002/ece3.10000
La Richelière, F., Muñoz, G., Guénard, B., Dunn, R. R., Economo, E. P., Powell, S., Sanders, N. J., Weiser, M. D., Abouheif, E., & Lessard, J. P. (2022). Warm and arid regions of the world are hotspots of superorganism complexity. Proceedings of the Royal Society B: Biological Sciences, 289(1968). https://doi.org/10.1098/rspb.2021.1899
Lanan, M. (2014). Spatiotemporal resource distribution and foraging strategies of ants (Hymenoptera: Formicidae). Myrmecological News, 20, 53–70.
Mason, K. S., Kwapich, C. L., & Tschinkel, W. R. (2015). Respiration, worker body size, tempo and activity in whole colonies of ants. Physiological Entomology, 40(2), 149–165. https://doi.org/10.1111/phen.12099
Shik, J. Z., Hou, C., Kay, A., Kaspari, M., & Gillooly, J. F. (2012). Towards a general life-history model of the superorganism: predicting the survival, growth and reproduction of ant societies. Biology Letters, 1–4. https://doi.org/10.1098/rsbl.2012.0463
Shik, J. Z., Santos, J. C., Seal, J. N., Kay, A., Mueller, U. G., & Kaspari, M. (2014). Metabolism and the rise of fungus cultivation by ants. The American Naturalist, 184(3), 364–373. https://doi.org/10.1086/677296
