To test whether the observed and expected distributions differed http://www.selleckchem.com/products/Liproxstatin-1.html significantly, we used a second script (Supporting Information Text S2) to calculate the distribution of median LF/HF values expected from intrinsic variation alone given the sample size available by calculating median LF/HF values for sets of simulated values

of the same sample size as the observed number of paired-queen colonies. This calculation was repeated 1000 times and the bottom 5% provided the cutoff for statistical significance. To determine the relationships among relative size differences, social dominance, excavation performance and reproduction, paired queens were ordered at random and the proportional difference between paired queens in each variable was calculated as the natural log of the ratio of the first over the second queen. For all variables except size, 1 was added to the individual queen values to prevent division by zero. This created an index symmetrical around 1 (equal values), with roughly half of pairs above 1 and half below for any given variable. We then tested for relationships among these variables using multiple linear regressions. Given the sequential nature

of dominance, excavation and reproductive behaviors, we analyzed each of these dependent variables against only those independent variables which preceded its expression (i.e. only size differences were considered to affect dominance, while both size and dominance were included when analyzing excavation). Although P. barbatus queens can be maintained in pairs, queens were generally aggressive toward one another Selleck Navitoclax when forced to associate. Over both years, PAK6 pairs of queens displayed at least one aggressive behavior in 78.5% of cases, ranging from 1 to 18 discrete aggressive actions displayed in a 15-min observation period. Of these,

in 47% (24 of 51 pairs) all aggression was displayed by one of the two queens. In the remaining pairs, aggressive behaviors were initiated to some extent by both queens. Aggressive behaviors did not appear to produce any visible injuries that could have physically impaired excavation behaviors. Aggressive behaviors were not more likely to be initiated by the larger queen in the pair (t53 = 1.05, P = 0.30, Fig. 1a). Despite the high level of initial aggression, continued aggression after excavation had commenced was relatively rare, observed between queens more than 2 hours after introduction in only 8 of the 65 total nests (12.3%). A queen performed at least one instance of excavation behavior in 61 of 63 single nests (97%) and in all 65 paired nests. Total excavations observed in single and paired nests did not differ in 2011 (singles: 15.33 ± 1.66 excavations, doubles: 14.14 ± 1.18; Student’s t-test, t53 = 0.71, P = 0.48) or in 2012 (singles: 33.97 ± 3.66, doubles: 40.18 ± 3.85; t53 = −1.17, P = 0.25; Fig. 2).