Genetic variability in geographic populations of the natterjack toad (Bufo calamita).

Across altitudinal and latitudinal gradients, the proportion of suitable habitats varies, influencing the individual dispersal that ultimately can produce differentiation among populations. The natterjack toad (Bufo calamita) is distributed across a wide geographic range that qualifies the species as interesting for a geographic analysis of its genetic variability. Five populations of B. calamita in the Sierra de Gredos (Spain) were studied in an altitudinal gradient ranging from 750 to 2270 m using microsatellite markers. In addition, we analyzed the latitudinal genetic variation in B. calamita within a global European distribution using genetic diversity parameters (mean number of alleles per locus [M(a)] and expected heterozygosity [H(E)]) obtained from our results and those published in the literature. The low level of genetic differentiation found between populations of B. calamita (F(st) ranging from 0.0115 to 0.1018) and the decreases in genetic diversity with altitude (M(a) from 13.6 to 8.3, H(E) from 0.82 to 0.74) can be interpreted by the combined effects of discontinuous habitat, produced mainly by the high slopes barriers and geographic distance. In the latitudinal gradient, genetic diversity decreases from south to north as a consequence of the colonization of the species from the Pleistocene refugium. We conclude that the genetic variability in B. calamita along its wide altitudinal and latitudinal geographic distribution mainly reflects the colonization history of the species after the last glacial period.

A comparative study on the paths of five anura species.

The movements of five species of European toads were recorded in the daytime and at night in a 3×3 m area. The paths obtained were analyzed according to the first order correlated random walk model developed by Bovet and Benhamou with which it is possible to characterize each path with two independent indices: its sinuosity and its speed. The analysis showed that the day/night variable affected the sinuosity of the paths but not their mean speed. Significant differences between species were found to exist, however, in the case of both the sinuosity and the speed. It is worth noting that these interspecific behavioural differences did not match the classical phylogenetic classification, as shown by multiple comparison tests.