Phenotypic selection in common toad (Bufo bufo)

Abstract

One of the most important problems for evolutionary biologists is to investigate the patterns and strength of phenotypic selection acting on quantitative traits in natural populations. Measurement of selection is complicated by the presence of correlations between characters; selection on a particular trait produces not only a direct effect, but indirect effects as well. Despite the growing body of phenotypic selection studies in a variety of taxa, studies on amphibians are still sparse. The aim of this study was to estimate patterns and strength of selection acting on a set of correlated characters in a natural population of Bufo bufo from the vicinity of Belgrade, Serbia. Morphological traits (body length, fore- and hind leg length) were measured, while fitness was assayed as fecundity and gonad weight for females and males, respec?tively. The regression approach was used to estimate selection differentials and gradients. Selection patterns differed between the sexes - linear selection differentials showed significant total directional selection for body size in females, but not in males. In males, differentials were significant for both fore- and hind leg lengths. Sample size did not permit identification of significant nonlinear (quadratic) selection.Jedan od najvaznijih problema za evolucione biologe je procena obrazaca i intenziteta fenotipske selekcije koja deluje na kvantitativne osobine u prirodnim populacijama. Procenu selekcije komplikuje i prisustvo korelacije izmedju osobina; selekcija koja deluje na datu osobinu ima ne samo direktan efekat na tu osobinu, vec i indirektan na raspodelu korelisanih osobina. Uprkos rastucoj kolicini informacija o fenotipskoj selekciji kod razlicitih taksona, studije na vodozemcima su jos uvek vrlo retke. Cilj ovog rada bio je da se procene obrasci i intenzitet selekcije koja je delovala na skup korelisanih osobina u prirodnoj populaciji Bufo bufo iz okoline Beograda. Merene su morfoloske osobine(duzina tela, duzina prednjih i zadnjih ekstremiteta); fitnes je procenjen preko fekunditeta kod zenki, odnosno tezine gonada kod muzjaka. Regresioni metod je primenjen za procenu selekcionih diferencijala i gradijenata. Obrasci selekcije su se razlikovali medju polovima - linearni selekcionih Diferencijali ukazuju na znacajnu ukupnu direkcionu selekciju za velicinu tela kod zenki, ali ne i kod muzjaka. Kod muzjaka, diferencijali su bili znacajni i za prednje i za zadnje ekstremitete. Zbog velicine uzorka nije bilo moguce naci znacajnu nelinearnu(kvadratnu) selekciju.