Reproductive cycle of the sand lizard (Lacerta agilis) in its southwestern range

The reproductive cycle of Lacerta agilis was studied in the Pyrenees at the southwestern boundary of the species range. The activity period is short (about 4.5 months). Males attain sexual maturity at smaller sizes than females and show mixed type spermatogenesis and spring spermiogenesis. Vitellogenesis in females is rapid (45 days for the whole population) with a long period of oviductal retention. Clutches are laid at the beginning of summer. During the reproductive period males mobilise reserves during the mating activities. Females deplete more fat reserves but later in the season than males and they are at their lowest after egg production. In both sexes. energy resources are mobilised from the fat bodies and also from the liver and the proximal part of the tail. Clutch size increases with female size but also depends on other factors. The short activity period does not appear to affect the reproductive cycle of this species. The gonad cycles and clutch traits do not show substantial differences from other European populations, perhaps with the exception of slight variation in the timing of reproductive events and, to a lesser extent, clutch frequency. This evidence strongly suggests that the limited southwestern range of Lacerta agilis not due to environmental constraints but to very recent colonization.