Behavioural and Mortality Data

Data on occurence of behavioural tasks, mortality rates and sporulation frequencies of Acromyrmex echinatior ants infected directly with Escovopsis (EwAnts) or Metarhizium (MbAnts) or indirectly through infection of the fungus garden (EwFungus and MbFungus respectively)

Differences in forage diversity.

<p>Differences in forage diversity between leaf-cutting ant species (nested within genera), using solid lines for <i>Atta</i> and dotted lines for <i>Acromyrmex</i>, and with typical foraging habitat indicated with dark green (forest), yellow (forest edge), and orange (open sunlit areas): (A) Heatmap showing differences between species and genera in the use of forage categories, with numbers representing mean proportions ±SE of the forage types. Darker colors indicate higher mean acquisition proportions, with the top-dendrogram illustrating similarities between species/genera across means of the five forage categories (vertical axis). Ant species names are given as abbreviations (volc, octo, echi, col, sex, cep). (B) Dendrogram based on the Inverse Simpson Diversity Index of the five forage categories, indicating the degree of evenness across foraging categories (numbers below the branches are mean D-values ±SE per species and means per genus), showing that <i>Acromyrmex</i> has a broader (more even) spectrum (D = 1.86±0.08 SE) of forage material than <i>Atta</i> (D = 1.42±0.13 SE; F_1,49 = 5.435, p<0.05). Numbers above the branch nodes represent Approximately Unbiased p-values (AU, red) and Bootstrap Probability values (BP, green).</p

Differences in foraging rate between loaded and unloaded foragers.

<p>Differences in foraging rate between loaded and unloaded foragers of <i>Atta</i> and <i>Acromyrmex</i> species in Gamboa, Panama, with summary statistics on the number of trails observed per species (number of colonies in brackets), the total number of minutes of observation per species, the total number of ants counted while returning to their nests, and the foraging rates for loaded and unloaded returning workers: means (± SE) per genus and per species (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094284#pone.0094284.s001" target="_blank">Table S1</a> for details).</p

Differences in fungus garden enzyme activity.

<p>Differences in fungus garden enzyme activity between species grouped as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094284#pone-0094284-g001" target="_blank">Figure 1</a> with solid lines for <i>Atta</i> and dotted lines for <i>Acromyrmex</i>, and with dark green, yellow and orange indicating the same habitat categories: (A) Heatmap showing differences between species and genera in fungus garden activity of enzyme classes, expressed as mean area in cm²±SE of colored halos on AZCL plates across all assays for enzymes belonging to the amylases (1), cellulases (2), hemicellulases (4), pectinases (3) and proteinases (2). Darker colors in the heatmap indicate higher mean activities, and the top-dendrogram illustrates similarities between species across all means for the five groups of enzymes, estimated by “pvclust” with 1000000 bootstraps. (B) Dendrogram based on the inverse Simpson Diversity Index of proportional enzyme activity showing that <i>Acromyrmex</i> fungus gardens have more even secretions across enzyme categories (D = 4.55±0.05 SE) than <i>Atta</i> (D = 4.18±0.07 SE, F_1,52 = 15.006, p<0.0001). Numbers above the branch nodes represent Approximately Unbiased p-values (AU, red) and Bootstrap Probability values (BP, green).</p

Differences in Forage-Acquisition and Fungal Enzyme Activity Contribute to Niche Segregation in Panamanian Leaf-Cutting Ants

<div><p>The genera <i>Atta</i> and <i>Acromyrmex</i> are often grouped as leaf-cutting ants for pest management assessments and ecological surveys, although their mature colony sizes and foraging niches may differ substantially. Few studies have addressed such interspecific differences at the same site, which prompted us to conduct a comparative study across six sympatric leaf-cutting ant species in Central Panama. We show that foraging rates during the transition between dry and wet season differ about 60 fold between genera, but are relatively constant across species within genera. These differences appear to match overall differences in colony size, especially when <i>Atta</i> workers that return to their nests without leaves are assumed to carry liquid food. We confirm that Panamanian <i>Atta</i> specialize primarily on tree-leaves whereas <i>Acromyrmex</i> focus on collecting flowers and herbal leaves and that species within genera are similar in these overall foraging strategies. Species within genera tended to be spaced out over the three habitat categories that we distinguished (forest, forest edge, open grassland), but each of these habitats normally had only a single predominant <i>Atta</i> and <i>Acromyrmex</i> species. We measured activities of twelve fungus garden decomposition enzymes, belonging to the amylases, cellulases, hemicellulases, pectinases and proteinases, and show that average enzyme activity per unit of fungal mass in <i>Atta</i> gardens is lower than in <i>Acromyrmex</i> gardens. Expression profiles of fungal enzymes in <i>Atta</i> also appeared to be more specialized than in <i>Acromyrmex</i>, possibly reflecting variation in forage material. Our results suggest that species- and genus-level identities of leaf-cutting ants and habitat-specific foraging profiles may give predictable differences in the expression of fungal genes coding for decomposition enzymes.</p></div