Reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the subtropical Wet Chaco of Argentina: geographical variations in response to local environmental pressures

Herein we studied the reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the Wet Chaco region (northeastern Argentina) and compared the results with other populations from the Espinal (central Argentina) and the Atlantic Forest (southeastern Brazil), and with other Neotropical species of Mabuya to better understand the possible causes of its reproductive phenotype variation. Males and females of M. dorsivittata from the Wet Chaco exhibited associated, seasonal, and annual reproductive cycles. Spermatogenic activity related positively to a lengthening photoperiod reaching maximum activity in late spring (December). Females displayed an extended gestation period of 11 months, from mid-summer (February) to late spring or early summer (December) when births occur. Embryonic development was associated with temperature and historical rainfall. Litter size ranged from 3 to 8 (mean = 5.3 ± 1.3 SD) and increased with body size and body mass of females. Fat-body mass varied seasonally and was inversely correlated with spermatogenesis and to embryonic development. Females were larger in body size and interlimb length, and smaller in head length than males. We observed interpopulational differences in minimum body size, litter size, and timing of birth, probably as a result of phenotypic plasticity, genetic divergence or both.