Lancaster used a combination of laboratory and field experiments to tease apart a complex set of interactions involving hormones, genetics, social interactions, behavioral strategies, and predators. Previous studies by Sinervo and his collaborators have described three different behavioral strategies that correlate with throat color in side-blotched lizards. Orange-throated males are highly aggressive and usurp territory from other lizards; yellow-throated males sneak into the territories of other males to mate with females; and blue-throated males form partnerships and cooperate to protect their territories. In females, throat color correlates with different reproductive strategies.
According to Lancaster, the maternal effect on back pattern is important because survival in these lizards depends on different combinations of traits in different circumstances. Females use social cues to predict the circumstances their progeny will encounter. Maternal influences like this probably occur in many species, but are very difficult to detect, Sinervo said.
"Maternal effects are a nebulous thing to study, because you know there are genes for these traits, and it's really hard to tell the maternal effects apart from the effects of the genes," he said.
Lancaster began by treating side-blotched lizard eggs with an array of different hormones. That revealed a striking influence of estradiol on back patterns. She also tested eggs from lizards captured in the wild and found a wide range of naturally occurring estradiol concentrations in the egg yolks.
The researchers then performed experiments in breeding enclosures, each holding one male lizard and three females. The numbers of orange- and yellow-throated females in each enclosure were experimentally varied, and throat colors of the males varied randomly. Lancaster tested eggs from each female's clutch for hormone levels and record
Source:University of California - Santa Cruz