Processes at the origin of similarities in dispersal behaviour among siblings

Abstract

Abstract Processes which generate natal dispersal are largely unknown. This is particularly the case for the sources of differences among families. Three types of processes can generate the variability among families: genetic, prenatal and postnatal. We first tested the family resemblance of dispersal behaviour in the common lizard (Lacerta vivipara). We then experimentally investigated the role of pre- and postnatal factors in the variability of dispersal among families. From 1989 to 1992, we studied dispersal of juveniles from pregnant females captured in the field and maintained in laboratory until parturition. We manipulated the conditions of gestation to test for prenatal effects on juvenile dispersal. We tested postnatal effects by releasing siblings of the same family in contrasted environments. We also examined covariances of natal dispersal with maternal and offspring traits. The results showed that: (1) dispersal behaviour was similar among siblings, (2) determinants of offspring dispersal differed between sexes and years, (3) offspring dispersal was related to litter sex-ratio and offspring corpulence at birth, (4) postnatal conditions influenced male dispersal, (5) short-term prenatal conditions (i.e. maternal conditions during gestation) influenced juvenile dispersal, varying per year, (6) long-term prenatal conditions (i.e. maternal conditions during gestation in the previous year) could also influence juvenile dispersal (marginally significant). Thus, several types of processes determine natal dispersal in the common lizard. Resemblance among siblings can partly be explained by both pre- and postnatal effects. The environment seems to be the major factor influencing juvenile dispersal in this species, i.e. dispersal essentially appears condition-dependent. The genetic basis of dispersal in vertebrates remains to be demonstrated by studies controlling for both prenatal and postnatal conditions.