Department of Ecology and Evolutionary Biology
My broad area of interest is in how organisms adjust growth and developmental in response to environmental variation. Specifically, I am focusing on the physiological mechanisms by which insects translate variation in diet quality and temperature, two environmental factors with strong effects on life histories, into phenotypic variation in body size and development time, two traits highly correlated with fitness. In my work I emphasize the regulation of these traits at the level of the whole organism. The complexity of the traits and the mechanisms that regulate them have led me to develop an integrative research program. Currently, I am employing techniques from quantitative genetics, physiology, endocrinology, ecology, evolutionary biology, behavior, and elemental stoichiometry, respirometry, combining lab, greenhouse and field work.
Here are some of the projects I am working on
The regulation of body size and its plasticity
(in collaboration with Fred Nijhout at Duke University)
In spite of the interest in the ecology and evolution of body size, remarkably little is known about the developmental and physiological mechanisms that determine body size, or how these developmental mechanisms change to result in plasticity of body size. The goal of our research is to understand these mechanisms. Our main findings so far show:
That there are three physiological factors that regulate body size and development time in the tobacco hornworm (Manduca sexta): (i) the timing of the cessation of juvenile hormone secretion in the last larval instar, (ii) the timing of ecdysone secretion and (iii) growth rate (Davidowitz and Nijhout, 2004).
These three factors can explain 95% of the variation in body size (D'Amico, Davidowitz and Nijhout, 2001).
These three factors also regulate development time (Davidowitz and Nijhout, 2004; Davidowitz, Roff and Nijhout, 2005).
The mechanism regulating phenotypic plasticity of size depends on the environmental signal: regulation of plasticity of size in response to diet differed from the mechanism regulating plasticity of size in response to temperature (Davidowitz, D'Amico and Nijhout, 2003; Davidowitz, D'Amico and Nijhout, 2004).
The same three factors that regulate plasticity in body size also regulate the evolution of body size (D'Amico, Davidowitz and Nijhout, 2001).
late last instar Manduca sexta
mechanism of body size regulation
(in collaboration with Derek Roff at UC Riverside and Fred Nijhout at Duke University)
Our understanding of the regulation of body size has led us to expand our research into a new area. The three factors that regulate body size are the same factors that regulate development time. Using simultaneous directional selection experiments, physiological and endocrine techniques as well as the analyses of the G and P matrices of the components of the mechanisms regulating size and development time, we are addressing a fundamental question in evolutionary biology: how do the underlying physiological mechanisms regulating growth and development constrain or enable the evolution of life history traits? Evolutionary biology has largely been restricted to the study of genetic correlation's between traits. We expect this study to reveal that the underlying causes of some genetic correlations, and their responses to selection may, in fact, be due to physiological coordinating mechanisms such as hormones (Davidowitz, Roff and Nijhout, 2005).
(In collaboration with Judith Bronstein and Travis Huxman, EEB, UofA)
of the mechanism regulating body size and development time comes from
work on a
lab colony of M. sexta
reared on artificial diet. We are now studying these mechanisms in an
ecological context in a natural population. M.
is both the major pollinator and major herbivore of Datura wrightii
Arizona. In collaboration with Judith
and Travis Huxman (EEB, UofA), we are quantifying the costs and
this interaction in the context of other herbivores and pollinators
the system. One focus is to study
how natural variation in the quality of host plants affects larval
growth of M.
caterpillars. By using our knowledge of
physiological and endocrine mechanisms regulating body size and
time in a natural ecological context, we have a unique opportunity to
at a mechanistic level, how two very important life history traits are
evolve in a natural setting.
Furthermore, we can bring this knowledge to bear on a wide range
timely questions regarding the ecological dynamics of alternating
and antagonistic plant/insect interactions.
pollen off proboscis of Eumorpha
||last instar Manduca sexta on Datura wrightii
||Datura wrightii in flower