Temporal and spatial variation in life history traits of the Japanese gecko, Gekko japonicus

Life-history variation has been widely reported for species with variable clutch size, but detailed data on reproductive strategies for species with invariant clutch sizes are scarce. We collected gravid female geckos (Gekko japonicus) from three geographically separate populations to examine geographic and annual variation in reproductive strategies. The majority of females produced a fixed number of eggs (n=2). Females from the southern population had larger body size, produced larger eggs, and had heavier clutches than females from two more northern populations, which was largely attributable to among-population differences in maternal body size. Within populations, female body mass varied between years; heavier females laid larger eggs and heavier clutches. The among-year difference in maternal body mass partly accounted for the annual variation in egg size and clutch mass. These results suggest that species with invariant clutch size can adjust egg size to increase or decrease per-clutch reproductive output.