Assessment of age and intersexual size differences in Bufo bufo

Abstract

Numerous studies have underlined the complex nature of relationship between age, size, and reproductive traits in anurans. One of the most intriguing problems for evolutionary biologists is intersexual difference in body size (SSD). For testing various hypotheses about SSD, we need reliable estimates of its extent (the important issue being the choice of trait for analysis) as well as the accurate determination of individual age. The measures of SSD may be subject to error if estimated from populations with unknown age distribution; amphibians continue to grow throughout their life and SSD is linked to sex differences in traits such as age at maturity and lifespan. In the present paper, we analyze problems involved in accurate determination of age structure and factors that may lead to under- or overestimation of individual age, as well as the problem of appropriate choice of traits, in the light of our experience and results of investigating populations of common toad (Bufo bufo) in the vicinity of Belgrade.Brojne studije istakle su složenu prirodu odnosa između starosti, veličine tela i reproduktivnih osobina kod bezrepih vodozemaca. Za evolucione biologe jedan od najintrigantnijih problema je interseksualna razlika u veličini tela (SSD). Za testiranje hipoteza koje se tiču SSD, neophodne su tačne procene njene veličine (izuzetno je važno pitanje izbora osobina koje se koriste u toj analizi), kao i precizno određivanje starosti. Procena SSD može biti pogrešna ako nije poznata uzrasna struktura date populacije; vodozemci nastavljaju da rastu tokom života, a SSD je povezana sa interseksualnim razlikama u osobinama kao što su vreme polnog sazrevanja i dužina života. U ovom radu analiziramo probleme vezane za tačnu procenu uzrasne strukture i činioce koji mogu da dovedu do precenjenih ili potcenjenih vrednosti, kao i probleme adekvatnog izbora osobina za analizu, s obzirom na naša iskustva i rezultate proučavanja populacija Bufo bufo iz okoline Beograda.Projekat ministarstva br. 172