Interspecific variation in subcaste brain structure scaling.

<p>Least-square mean (± s. e. m.) brain subregion sizes from ANCOVA model (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031618#pone-0031618-t003" target="_blank">Table 3</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031618#pone.0031618.s002" target="_blank">Table S1</a>) illustrating significant species×subcaste interactions for ln-transformed (<b>A</b>) subesophageal ganglion volume, (<b>B</b>) mushroom body peduncle and lobes volume, and (<b>C</b>) antennal lobe volume. Numbers above pairs of bars are major-to-minor-worker ratios of (untransformed) least-square means for each species. Key: grey bars, minor workers; open bars, major workers.</p

<i>Pheidole</i> subcastes and age groups have neural phenotypes that are well separated in multivariate space.

<p>Plot shows the separation of all 12 worker groups on the first two canonical variables generated by discriminant analysis (accounting for 87% of the total variance explained by the analysis). Four non-overlapping clusters (dotted ellipses) are generated by very strong discrimination among young minors, old minors, young majors, and old majors. Key: red, <i>P. dentata</i>; green, <i>P. morrisi</i>; blue, <i>P. pilifera</i>; open, young age cohort; closed, mature age cohort; circles, minor workers; squares, major workers; crosses, group centroids.</p

Between-group grade shifts in <i>Pheidole</i> brain subregion scaling are indicated by significant ANCOVA effects.

<p>Factor main effects are not listed for significant interaction terms. Grade shift descriptions are based on inspection of marginal means. Full ANCOVA model details are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031618#pone.0031618.s002" target="_blank">Table S1</a>.</p

Brain-to-body-size scaling in <i>Pheidole</i> workers.

<p>Least-square mean (± s. e. m.) relative brain volumes from ANOVA model (mature workers only) indicating significant (<b>A</b>) species and (<b>B</b>) subcaste effects. Levels not sharing the same letter are significantly different ([<b>A</b>]: Tukey-Kramer <i>post hoc</i> comparisons of least-square means; [<b>B</b>]: main effect of subcaste).</p

Results of discriminant function classification of worker brains to the <i>a priori</i> groups listed.

<p>Each row indicates classification outcomes using either the full discriminant model or the jacknifed (leave-one-out) model for the given analysis. Significant Press' <i>Q</i> statistics indicate that workers in a given analysis were classified to the correct <i>a priori</i> group at greater-than-chance levels.</p

Patterns of behavioral and sensory neuropil variation are concordant between worker age cohorts and subcastes.

<p>Patterns of behavioral and sensory neuropil variation are concordant between worker age cohorts and subcastes.</p

Examples of altered brain scaling relationships.

<p>Solid and dashed lines in (<b>A</b>–<b>C</b>) indicate hypothetical standardized major axis (SMA) scaling relationships of brain region volume (y variable) with brain size (x variable). (<b>A</b>) Altered slopes (β1 and β2), which preclude further scaling analyses using these methods. (<b>A</b>). Groups share a common scaling slope and y-intercept (y1) but average brain size differs between groups (×1 and ×2), producing an x-axis shift. (<b>C</b>) Groups share a common scaling slope and average brain size (×1) but y-intercepts (y1 and y2) are shifted, producing a grade shift. (<b>D</b>) Solid and dashed lines represent actual SMA scaling regressions of mushroom body volume versus remainder-of-central-brain volume (ROCBV) for mature <i>P. pilifera</i> minors (circles) and mature <i>P. pilifera</i> majors (squares), representative of a grade shift accompanying a shift along the x-axis. Dashed line in (<i>d</i>) indicates slope of 1 (isometry) for reference.</p

<i>Pheidole</i> worker morphology and neuroanatomy.

<p>(<b>A</b>) Mature <i>P. pilifera</i> minor (left) and major (right) workers. (<b>B</b>) <i>P. dentata</i> mature (left) and young (right) major workers, identifiable by cuticle colour. (<b>C</b>) Confocal micrograph of a <i>Pheidole</i> worker brain in horizontal section showing regions of neuropil. Central brain subregions visible in this section are pseudocolored. Section is slightly oblique, only one optic lobe is visible in the plane of sectioning. (<b>D</b>) 3D reconstructions of the brain shown in (<b>C</b>). Central brain functional subregions are rendered solidly, other central brain neuropils are transparent grey, and the subesophageal ganglion is a point cloud. Key: a, anterior; p, posterior; d, dorsal; v, ventral; l, lateral; green, antennal lobe; orange, central body; red, mushroom body medial calyx; yellow, mushroom body lateral calyx; blue, mushroom body peduncle & lobes; purple, optic lobe. Scale bars are 1 mm in (<b>A</b>) and (<b>B</b>) and 50 µm in (<b>C</b>) and (<b>D</b>).</p

Biogenic amine and aggression assay data

Behavioral data for all four aggression assays and biogenic amine measurements for interspecific aggression assays and OA topical treatment assays in minor workers

Brood care time

Brood care tim