Figure 1.

Size-related pairing patterns between the females and the first males guarding them at the (a) LC and (b) HC sites. Residual sizes (prosoma width, mm) are shown and used in analysis: they reflect the competitive ability of a male relative to other males of his site, and the relative fecundity of a female among pre-moulting females of her site. After randomly selecting only one guarding event per male, we found a strong difference in size-assortative pairing between the two sites (effect of the female size–site interaction on male size: two-way ANOVA; F_1,56=8.357, p=0.005). The first pairs were not assorted by size at the LC site ((a), 44 females paired with 28 distinct males, Student's t-test, t₅₆=1.088, p=0.28) but they were at the HC site ((b), 34 females paired with 31 distinct males, estimate±s.e.=0.709±0.234; Student's t-test, t₅₆=3.034, p=0.003).