Sexual size and shape dimorphism of the Vipers at the Balkans - small, medium and large scale

Abstract

We examined the degree and direction of sexual size dimorphism (22 traits measured) and sexual shape dimorphism (14 traits measured) in three Viper species from the Balkan Peninsula (Vipera ammodytes, V. berus and V. ursinii). We used three populations of Vipers (one per species) with relatively large sample sizes: 94 adult nose-horned viper (44 females, 50 males), 38 adult adders (33 females, 5 males) and 138 adult meadow vipers (93 females, 45 males). Data from additional populations were also analysed: 733 adult nose-horned vipers (370 females, 363 males), 85 adult adders (56 females, 29 males) and 181 adult meadow vipers (120 females, 61 males). General trends were inconsistent across species and populations: males tended to be larger in V. ammodytes but not in V. ursinii for instance. One population of V berus contained larger males compared to females, but this pattern was not found in other populations. Such instability in many traits assessed seriously complicates any attempt to generalise the respective effects of proximate and ultimate factors. The good news is that careful long-term CMR field studies are more than ever essential for fundamental and conservation purposes.