The effects of breeding density, year, and laboratory vs. field environments on plasma and yolk steroids in green anole lizards ( Anolis carolinensis)

Scope and method of study. My objectives were to: (1) determine how breeding density and year affect plasma and yolk T and CORT concentrations in a laboratory environment; and (2) document female plasma and yolk T and CORT concentrations in a field environment. Breeding females were housed in cages with either one male (low density) or one male and three additional females (high density) to evaluate the effects of breeding density on reproductive effort and plasma and yolk testosterone (T) and corticosterone (CORT) concentrations. All laboratory animals were maintained under standard breeding conditions for ten weeks over the course of two breeding seasons. Nest boxes were checked daily for eggs which were frozen for subsequent yolk steroid analyses. At the end of the study, blood samples were collected from all laboratory animals. Blood samples and eggs were collected from wild-caught females. All blood and yolk samples were analyzed using radioimmunoassay.;Findings and conclusions. I found that breeding density did not affect male initial body condition, but did affect male final body condition and change in body condition. A significant year effect was seen in male initial, final, and change in body condition. Breeding density did not affect female body condition, but year effects were seen in female initial and change in body condition. Egg mass was affected by year, but not breeding density. Surprisingly, females in low density cages produced more eggs than females in high density cages and year also affected egg production. Female and male plasma CORT and T concentrations were unaffected by breeding density or year, except males in high breeding densities tended to have higher plasma T concentrations and females in 2008 had higher plasma CORT concentrations than females in 2007. Yolk T and CORT concentrations were affected by year and yolk CORT concentrations tended to be higher in eggs from high breeding densities, rather than low breeding densities. In comparison with field data, eggs from females in the laboratory were heavier, but had lower levels of yolk T and CORT. Wild-caught females tended to have greater mass and SVL than laboratory females, but laboratory females had higher concentrations of plasma CORT.