Life-History
The MANOVA showed statistically significant differences in reproductive life-history traits between core and edge, populations, and eclosion dates (range: Pillai–Bartlett statistic=0.093, p<0.001; population: Pillai–Bartlett statistic=0.133, p=0.046; eclosion date: Pillai–Bartlett statistic=0.359, p<0.001). Across all three traits, reproduction increased about 7% at the edge compared to core.
In the univariate analysis, mass of females at adult emergence ranged from 6.5 to 14.7 mg. Females from the edge of the range were larger than females from the core on average (core mass=9.65 mg SE=0.163; edge mass=10.30 mg SE=0.160; F=8.04, p=0.030; Fig. 3A).
The number of eggs from the first day of reproduction ranged from 0 to 30. The proportion of beetles laying eggs during the study did not differ between the core and edge (core proportion=0.813, edge proportion=0.845, c2=0.46, p=0.499). Of those that oviposited during the study, edge beetles tended to be more fecund (core eggs=10.9, SE=0.40; edge eggs=12.0, SE=0.40; c2=3.39, p=0.067; Fig. 3B). Age at first reproduction was not a predictor of the number of eggs laid (c2=0.01, p=0.916), but larger females laid more eggs (c2=5.79, p=0.016).
Age at first reproduction ranged from three to seven days after adult emergence. From the regression analysis, edge beetles tended to reproduce earlier than core beetles (core age=5.51 days, SE=0.11; edge age=5.24 days, SE=0.10; c2=3.64, p=0.058; Fig. 3C). Mass at emergence was not a predictor of age at first reproduction (c2=1.92, p=0.166). Results were similar in the Kaplan-Meier survival analysis. Median age at first reproduction was 5 days (95% CI: 5, 6) for edge and 6 days (95% CI: 6, 6) for core (Fig. 3D). The log-rank test for differences in survival curves indicated marginal differences between core and edge (c2=3.8, p=0.051).
The mass of males at the time of the dispersal trial (thus, after feeding ad libitum) ranged from 6.9 to 19.3 mg. There was no difference in mass of males between core and edge populations (F=0.67, p=0.445). Older beetles weighed more than younger beetles (F=46.55, p<0.001) and males reared at high density weighed more than those reared at low density (high mass=12.2 mg, SE=0.134; low mass=11.8 mg, SE=0.135; F=15.09, p<0.001).