Relatedness facilitates cooperation in the subsocial spider, Stegodyphus tentoriicola

Table 3 Influence of treatment (non-sib/sib) on relative per capita mass increase, mean body weights within groups before and after the experiment, and CV on body weights before and after experiment in groups of 3 (A) and 6 (B) spiders

	non-sibs	sibs	statistics	p
A Groups of 3 spiders
Relative mean mass increase	0.39 ± 0.09 (9)	0.30 ± 0.03 (12)	Z = 0.75	0.46
(1 extreme outlier removed)	0.31 ± 0.03 (8)	0.30 ± 0.03 (12)	Z = 0.35	0.73
Mean body weights of groups before experiment [mg] (± SE mean)	4.65 ± 0.55 (10)	3.57 ± 0.24 (12)	t = -1.9	0.07
Mean body weights of groups after experiment [mg] (± SE mean)	14.42 ± 1.90 (9)	15.05 ± 2.16 (12)	t = -0.45	0.66
CV before experiment (± SE mean)	0.08 ± 0.014 (10)	0.07 ± 0.009 (12)	Z = 0.23	0.82
CV after experiment (± SE mean)	0.28 ± 0.080 (8)	0.16 ± 0.024 (12)	Z = 1.12	0.26
B Groups of 6 spiders
Relative mean mass increase	0.33 ± 0.02 (10)	0.31 ± 0.03 (9)	t = -7.73	0.48
Mean body weights of groups before experiment [mg] (± SE mean)	3.63 ± 0.19 (10)	4.01 ± 0.38 (10)	t = 0.93	0.37
Mean body weights of groups after experiment [mg] (± SE mean)	11.10 ± 0.55 (10)	13.37 ± 0.85 (9)	t = 2.40	0.028
CV before experiment (± SE mean)	0.099 ± 0.01 (10)	0.067 ± 0.01 (10)	t = -2.47	0.024
CV after experiment (± SE mean)	0.33 ± 0.04 (10)	0.19 ± 0.02 (9)	t = -2.21	0.041

Means and SE are given and sample sizes in brackets (non-parametrical Wilcoxon test (Z) or parametrical t-tests (t) were performed).

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