Results
Mite loads, mite load ranges, and growth rates of male and female
yearling lizards are summarized in Table 1. Overall, growth rate was
negatively correlated with SVL, higher in females than in males, and
higher in 2019 than in 2016 (Figure 1; overall: F3,82 =
25.97, p < 0.001; effect of sex: (F3,1= 30.91, p < 0.001; effect of year:
(F3,1 = 16.52, p = 0.001). Sex differences in
growth rate were similar in 2016 and 2019, resulting in the development
of significant sexual size dimorphism (SSD) early in July of both years.
In 2019, for example, the difference between female and male SVL, and
thus the development of SSD, had become statistically significant by 14
July (Figure 2; F1,25 = 5.24, p = 0.031).
Mite loads tended to increase with body size (SVL) in June and in July,
although in both months these size effects failed to achieve
conventional statistical significance (Figure 3; June:
F3,1 = 3.17, p = 0.077; July: F3,1 =
3.78, p = 0.055). Controlling for SVL, mite loads were higher on
males than on females in July (F3,1 = 6.63, p =
0.011), but not in June (F3,1 = 0.09, p = 0.764),
and were higher in 2019 than in 2016 in June (F3,1 =
8.32, p = 0.004) but not in July (F3,1 = 0.83,p = 0.364).
Growth rate was not correlated with mite load in June or in July (Figure
4). Residual values used for these analyses remove variation due to
differences in SVL, sex, and year, thus allowing the analysis to focus
solely on a potential correlation between growth rate and mite load. In
both June and July, correlations between residual variation in growth
rate and residual variation in mite load were convincingly
non-significant (June: F1,84 = 0.08, p = 0.777,
R2 = 0.001; July: F1,70 = 0.12,p = 0.727; R2 = - 0.012).
Similarly, mite load had little effect on body condition. In June, the
negative effect of mite load on body condition attained marginal
statistical significance (Figure 5; F1,140 = 4.16,p = 0.043, R2 = 0.022), while in July
this relationship was not statistically significant
(F1,98 = 1.28, p = 0.261,R2 = 0.003).