Developmental and early life-history correlation patterns
We investigated the pattern of correlation between all recorded life-history traits, including recorded developmental stages of embryos at three checkpoints during embryonic development. We calculated a correlation matrix for all analysed traits (11 × 11) separately for each species (Table 2).
Even though the phenotypic correlation matrices for some species were calculated for a relatively small number of cohorts (N = 19 in T. cristatus), the estimated matrices were highly reproducible and reliable (Table 3).
We found no correlation between the time of egg deposition and the number of deposited eggs per cohort, with the exception of T. dobrogicus, which exhibited a significant positive correlation between oviposition time and the number of eggs laid per cohort (Table 2). There was no correlation between the number of deposited eggs and vitellus size in any of the four species. A significant negative correlation was found between the vitellus size (RV) and the duration of embryonic period in T. macedonicus, while there was no significant relation between these two traits for other species. However, there was a strong positive correlation between the duration of embryonic period and the size of hatched larvae, except in T. cristatus (Table 2).
We applied Mantel’s test to explore interspecific similarities in the correlation of life-history traits. Based on this analysis, the correlations of life-history traits in T. cristatus were concordant with the pattern observed in T. dobrogicus (R = 0.597, P < 0.05), but were not similar to the other two species. The life-history trait correlation of T. dobrogicus alsoshowed significant concordance with T. macedonicus (R = 0.688, P < 0.01), while the matrix correlation between T. dobrogicus and T. arntzeni was insignificant(R = 0.266, P > 0.05). Triturus arntzeni had a similar correlation pattern to T. macedonicus (R = 0.450, P < 0.05), but there were no similarities in the matrix correlation pattern compared to the other two species.