O. Gy. Dely szerk.: Vertebrata Hungarica 22. (Budapest, 1984)
Korsós, Z.: Comparative niche analysis of two sympatric lizard species (Lacerta viridis and Lacerta agilis) 5-14. o.
On the basis of a resource utilization function of the food size as a niche dimension we can obtain information about niche width of a species (ROUGHGARDEN 1974). From data on average prey sizes, their frequency distributions and variances, and on the snout-ear distances of adult sand and green lizards the following niche widths have been calculated: L. viridis L. agilis total niche width 60.0 67.8 within phenotype component 96.8 % 78.5 % between ph. comp. 3.2 % 21.5 % niche position 14.3 mm 11.8 mm In both species individual variability accounted for the greater part of total variance (see Discussion). That means that the animals are rather generalists with respect to food size. Fig. 6. Frequency distributions of discriminant scores of lizard head measurements DISCUSSION Differential adaptation to temperature and light conditions plays an Important role in the microdistribution of poikilotherm lizards. The populations with different tolerance aspects maintain different relationships with the environmental factors affecting them. This situation Is manifested in the geographical distribution of the two species as well. L. agilis is widespread through nearly the whole of the Palaearctic between the 40th and 60th degrees of latitude, but the other species shows greater preference for warmth. It occurs only south of the 52th degree of latitude. The other closely related species (L. trilineata, L. leplda, L. schrelberi) occur mostly in the Mediterranaeum (ARNOLD et al. 1978). Accordingly, L. viridis prefers higher soil temperature, as contrasted with L. agilis , which has a greater tolerance for variation in air temperature and light intensity. Since the two lizard populations have a common biotope In the study area, they cannot segregate by partitioning the given microclimatic conditions, but they can optimize their coexistence by utilizing different periods of the day and the whatever vegetational microheterogeneity there is. According to some authors (VASVÁRI 1927, ARNOLD et al. 1978) It Is presumable that the green lizards would prefer microhabitats with dense woody and bushy vegetation. A hypothesis that this microhabltat selection could be detected by examining the dispersion pattern of the green lizard population in comparison with that of the vegetation, had arisen previously (KORSOS 1982).The results clearly show that there Is no significant difference between the vegetation requirements of the two species. However, in Fig. 7 we can see another possible interpretation. In summer days the green lizards spend the dlsadvantageously sunny and warm hours of high noon In the shadow of bushes and shrubs. Thus the relative frequency of L. viridis specimens observed In dense woody vegetation increases and at the same time their occurrence decreases in the open microhabitats.
