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

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: http://periodictable.com/Elements/080/

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).

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

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

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.

Dorsal cranium PCA

Ventral cranium PCA

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 0.0022 for the mines and 0.0018 for the quarry.

Procrustes distances between populations, and results of the permutation test (10 000 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

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.

Regression scores, dorsal cranium

Regression scores, ventral cranium

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.).

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