Table 3.

Spearman rank correlation coefficients (r_s) testing the relationship between the size of elytra and abdomens (= sample mass) and concentrations of 12 chemical elements measured in various Stag Beetle Lucanus cervus populations (see Fig. 1 and Table 1 for the origin of the populations) with sample sizes n > 10; the statistically significant relationships are in bold; * P ≤ 0.05, ** P < 0.01, *** P < 0.001.

Sample/population acronym	Number of samples	Ca	Mg	K	Na	Mn	Fe	Zn	Cu	As	Cd	Pb	Ni
ELYTRA
All populations	271	−0.299***	−0.251***	0.109	0.195***	0.071	−0.281***	−0.214***	−0.350***	−0.262***	−0.461***	−0.478***	−0.175**
BEL_Sol	12	0.091	0.112	0.322	0.196	0.189	−0.014	−0.259	−0.336	0.126	−0.427	−0.503	−0.706**
BEL_Spe	33	−0.218	−0.274	−0.122	−0.079	−0.115	0.080	−0.050	−0.417*	−0.130	−0.412*	−0.164	−0.156
GER_Ko	11	0.382	0.173	0.209	0.164	−0.282	−0.336	−0.364	−0.555	−0.709*	−0.636*	−0.436	−0.227
GER_Ta	18	−0.172	−0.459	−0.020	0.267	−0.115	−0.366	0.121	−0.441	−0.156	0.117	−0.232	−0.521*
ITA	11	0.345	0.345	−0.555	−0.700*	−0.055	0.564	−0.500	−0.645*	−0.055	−0.318	−0.409	0.436
POL_Łsz	12	−0.049	−0.042	0.483	0.000	0.594*	0.350	0.161	−0.035	−0.252	0.007	−0.734**	−0.636*
POL_Prz	30	−0.459*	0.041	0.055	0.223	0.334	0.131	−0.365*	−0.107	−0.001	−0.503**	−0.310	−0.458*
POL_Wł	10	−0.912***	−0.505	−0.255	0.097	−0.918***	−0.894***	−0.243	−0.322	−0.723*	−0.365	−0.705*	−0.274
Slo_MS3	10	0.024	0.644*	0.413	0.298	0.973***	−0.347	0.480	−0.030	−0.681*	−0.328	−0.681*	0.407
SPA_La	17	−0.735***	−0.554*	0.294	0.098	0.017	−0.400	0.529*	−0.664**	−0.289	−0.127	−0.483*	−0.228
UK_Col	14	−0.714**	−0.490	−0.789***	−0.244	−0.516	−0.811***	−0.644*	−0.587*	−0.719**	−0.484	−0.732**	−0.226
UK_Fet	12	0.350	0.007	0.699*	0.524	0.070	0.811**	0.196	−0.203	0.874***	0.105	−0.168	0.469
ABDOMENS
All populations	124	−0.312***	0.042	0.327***	0.295***	−0.004	−0.123	−0.355***	0.041	−0.127	−0.513***	−0.515***	−0.457***
BEL_Spe	19	−0.282	−0.212	0.226	0.116	0.142	0.516*	−0.075	−0.253	0.026	0.023	0.181	−0.325
POL_Prz	15	−0.425	0.129	0.232	0.407	−0.504	−0.429	−0.600*	0.454	0.604*	−0.357	−0.471	−0.404

Additional comment on the data inTable 3.

Given the apparent sexual dimorphism in body size in Stag Beetles, our findings suggest that sex-related differences in ETs for some of these metals can occur in this species. Sex-related differences in the contents of major nutrients and trace elements have been described in dimorphic insects, and it has been hypothesized that this can have certain consequences for their reproduction [15]. To date, given that female Stag Beetles are the smallest individuals [9; see Photo 1], we can speculate that they tend to accumulate relatively more Zn, As, Cd and Ni in both abdomens and elytra, and more Pb and Mg in their abdomens and elytra, respectively. At the same time, higher abdomen K concentrations may be indicative of larger males. These findings are therefore a clear incentive for further detailed assessments under controlled conditions of how ETs in different body parts of beetles and other insects vary with sex and body size heterogeneity – the rule in a population but often overlooked in the stoichiometry/elemental study of insects – and relating this to reproductive indices and landscape heterogeneity.