1. Effect of Mercury on Wall Lizard (Podarcis muralis) Populations: Cranial Morphology and Allometry – Preliminary Results
Aleksandar UROŠEVIĆ1, Milena CVIJANOVIĆ1, Tanja VUKOV1, Saša JANKOVIĆ2, Dragica NIKOLIĆ2, Maja SLIJEPČEVIĆ1, Marko ANĐELKOVIĆ1 and Nataša TOMAŠEVIĆ-KOLAROV1
University of Belgrade, Institute for Biological Research „Siniša Stanković“, Department of Evolutionary Biology, Belgrade, Serbia
Institute of Meat Hygiene and Technology, Department for Residue Examination, Kaćanskog 13, 11000, Belgrade, Serbia

2. Mercury is a liquid heavy metal,
mostly found as a mercuric sulfide.
Mercury and most of its compounds
are highly toxic and exceedingly
bioaccumulative.
Mercury can be released into
the environment in its inorganic and
organic forms.
Chronic exposure to mercury affects
early development and can lead to
defects and malformations.
Image from:

3. To estimate possible effect of chronic mercury exposure on the cranial morphology and post-natal development, we collected 45 specimens of juvenile and adult wall lizards from the Šuplja Stena mercury mine tailings (mt. Avala, Belgrade, Serbia).

4. As a control group, we collected 39 individuals from the nearby rock quarry in Ripanj, less than 2km away. 2 1

5. Mercury was present in both groups, but concentrations of mercury were significantly higher in the population from the Šuplja Stena mine tailings.

6. To test for morphological differences between two populations, we employed Procrustes-based geometric morphometrics on the dorsal and ventral cranium structures.
We used the standard landmark set we employed in the previous studies of the Lacertid cranial morphology.

7. Dorsal cranium PCA

8. Ventral cranium PCA

9. The results of ANOVA confirmed significant sexual dimorphism in both populations, for both size and shape (p<0.05).
Juveniles, females and males did not differ in size and shape between the populations (p>0.05).
The Sex × Population interaction was not statistically significant (p>0.05): the pattern of sexual dimorphism in size and shape is the same in both populations.
The total shape variance (from the PCA) was for the mines and for the quarry.

10. Procrustes distances between populations, and results of the permutation test
( rounds)
Dorsal cranium
Ventral cranium
Proc. Dist. p
Juv
0.0199
0.19
0.0155
0.2155
Female
0.0121
0.1339
0.1159
Male
0.0147
0.1907
0.0162
0.0164

11. In both populations, static and ontogenetic allometry were significant
In both populations, static and ontogenetic allometry were significant. However, static allometric and ontogenetic allometric trajectories did not differ between populations.
Allometry
Static
Ontogenetic
% explained p
Dorsal
Quary
30.07
<.0001
44.72
Mine
22.21
49.53
Ventral
34.93
56.36
26.5
65.72
Vector
comparison:
24.51
13.43
17.78
9.67
For angle comparison, permutation test was against the null hypothesis that
allometric vectors have random directions.

12. Regression scores, dorsal cranium

13. Regression scores, ventral cranium

14. Conclusions
Although both populations are exposed to mercury, the population from the mine tailings accumulated mercury multifold compared to the control group.
Patterns of general cranial morphology and allometry are apparently well conserved among the studied populations.
These traits remained stable regardless to the level of exposure to pollution.
The structures of cranium are morphologically complex and functionally important. The stabilizing selection most likely compensates for the effects of chronic exposure to mercury.
Further analyses should focus on subtler patterns of shape variation (FA), molecular response to environmental stress (stress enzymes) and test for the effects of various other pollutants (Lead, pesticides, etc.).

15. Thank you!