Table 1.
Comparisons of zero-inflated beta mixed-effect regression models examining the effects of size, relative size, sex, and their interactions on aggression in (A) Pairs, (B) 2M1F Trios, and (C) 2F1M Trios of A. maritima on San Juan Island, WA in 2016. Model formula reflects both the zero-inflation and conditional portions of the model.
Table 2.
Results from zero-inflated beta mixed-effect regression models examining the effects of relative size, and sex on aggression in (A) Pairs, (B) 2M1F Trios, and (C) 2F1M Trios in A. maritima on San Juan Island, WA in 2016. Proportion of aggressive acts, defined as the number of strikes divided by the number of interactions, was the response variable.
Table 3.
Descriptive summaries of copulatory activity by size and sex classes in Pairs, 2M1F Trios, and 2F1M Trios in A. maritima on San Juan Island, WA in 2016. The data (x/ N) represent the number of trials in which an individual of a size class engaged in copulatory activity (x) relative to the number of trials in which that size class was present (N)*. In 2M1F Trios and 2F1M Trios, there was one instance where both same-sex individuals engaged in copulatory activity within a single trial. In Pairs, females accepted courtship from both large and small size classes at equal rates. However, in 2M1F Trios, females more frequently accepted copulatory activity from the larger of the two males. Chi-square tests in the text reflect individual-level weighted availability.
Table 4.
Comparisons of generalized linear models of copulatory activity in (A) Pairs, (B) 2M1F Trios, and (C) 2F1M Trios of A. maritima on San Juan Island WA in 2016. (F = Female, M = Male, LF = Larger Female, SF = Smaller Female, LM = Larger Male, SM = Smaller Male).
Table 5.
Results of generalized linear models of copulatory activity in Pairs (A), 2M1F Trios (B), and 2F1M Trios (C) of A. maritima on San Jauan Island, WA in 2016. Predictor variables were selected using stepwise selection to construct a set of candidate models. Model performance was evaluated using Akaike’s Information Criterion (AIC), and results are reported for the lowest AIC model in each trial type. (F = Female, M = Male, LF = Larger Female, SF = Smaller Female, LM = Larger Male, SM = Smaller Male).
Fig 1.
Likelihood of copulatory activity as a function of female strikes and size in Pairs of A. maritima, San Juan Island, WA, 2016.
This figure visualizes the significant interaction reported in Table 5A, where each point represents the outcome of a single Pairs trial. Predicted probabilities (solid lines) are shown with 95% confidence intervals (shaded areas). “Average” (orange) corresponds to mean pronotum width while “Small” (green) and “Large” (purple) correspond to a pronotum width 2 standard deviations above and below the mean respectively. As female absolute size increases, the effect of strikes on the likelihood of copulatory activity decreases.
Fig 2.
Likelihood of copulatory activity as a function of female-to-smaller male strikes and male size discrepancy (larger male to smaller male relative size) in 2M1F Trios of A. maritima.
This figure visualizes the significant interaction shown in Table 5B, where each point represents the outcome of a single 2M1F Trio trial. Predicted probabilities (solid lines) are shows with 95% confidence intervals (shaded areas). “Average” (orange) corresponds to mean male size discrepancy while “Small” (green) and “large” (purple) correspond to a size discrepancy 2 standard deviations above and below the mean respectively. As male size discrepancy increases, the effect of female-to-smaller male strikes weakens and eventually reverses.