Dominance and reproduction in a parthenogenetic lizard

Hazards inherent in interdisciplinary behavioral research

Many, if not all, questions in biology and psychology today were formulated and considered in depth, though typically in a different language, from the 1700's to the early 1900's. However, because of politics or fashion, some topics fell out of favor or failed to recruit new scientists and hence languished. Despite greatly expanded scholarship in the history of the life sciences in the twentieth century, many such topics have had to be rediscovered in recent years, while much of the wisdom already accrued stays in the older literature and not in active minds. This is particularly true today when scientific advances appear at breakneck speed. It would not be an exaggeration to say that many 'breakthroughs' turn out really to be rediscoveries of forgotten observations. Two areas of particular significance to the interdisciplinary study of behavior are the Norms of Reaction (from Biology) and the concept of Plasticity (from Psychology). These and related fields benefit from the perspective of epigenetics so long as rigorous operational definitions are implemented. It is also important to revive Hogben's admonition that the interaction of hereditary and environment cannot be understood outside of the context of development. Five examples of increasing complexity in phenotypic plasticity in brain and behavior are presented to illustrate this perspective.

Endocrine and behavioral responses to aggression and social dominance in the green anole lizard, Anolis carolinensis

Adult males of the small arboreal iguanid lizard, Anolis carolinensis, will fight and form social dominance hierarchies when placed in habitats with limited resources. The relationships between time since initial aggressive interaction, relative social dominance, reproductive activity, and corticosterone and androgen levels were determined for 34 pairs of lizards. A discriminant analysis established a "dominance index" which indicated that over 90% of the difference between individuals who had won or lost aggressive interactions (putative social dominants and subordinates) was attributable to a single discriminant function reflecting altered body color, perch site selection, and circulating androgen. Animals that had darker body color also selected lower perch sites and had depressed rates of courtship relative to winners of fights and were thus designated as social subordinates. These animals also had levels of circulating androgen significantly lower than that of dominants, but circulating corticosterone was not significantly affected. Winners of fights showed a dramatic surge in circulating androgen at 1 hr but returned to near control values by 1 week; losers, however, showed depressed circulating androgen levels at 1 week.

Ovarian and adrenal function in the parthenogenetic whiptail lizard Cnemidophorus uniparens in the field and laboratory

The purpose of this study was to document circulating concentrations of corticosterone in the plasma in relation to the ovarian follicular cycle in animals in the field and to examine the effects of captivity and laboratory manipulations on plasma corticosterone in the parthenogenetic whiptail lizard Cnemidophorus uniparens. In nature, circulating concentrations of corticosterone are highest in previtellogenic individuals when concentrations of progesterone are basal and estradiol-17 beta is undetectable. In vitellogenic lizards, circulating concentrations of corticosterone decline from previtellogenic levels while concentrations of progesterone and estradiol-17 beta increase. In preovulatory individuals, corticosterone concentrations are basal, while progesterone and estradiol-17 beta levels are maximal. Following ovulation, corticosterone and progesterone remain at preovulatory concentrations and estradiol-17 beta is undetectable. Ovariectomy elevates circulating concentrations of corticosterone, as does cold and handling. Individuals housed either in isolation or in groups of three per cage exhibit circulating concentrations of corticosterone similar to those measured in the plasma of animals immediately after being captured in the field. The effects of ovariectomy and cold/handling manipulations were additive. No nonadditive effect (statistical interaction) was revealed. These results document complementary and reciprocal effects of ovarian and adrenal gland function with respect to hormonal changes both in the field and as a result of experimental manipulations in the laboratory. However, relationships between ovarian and adrenal function appear to be complex. Several overlapping hypotheses are offered as possible explanations of the results and as potential avenues for further investigations.