Evolutionary Endocrinology: The Developing Synthesis between Endocrinology and Evolutionary Genetics

Abstract

A productive synthesis of endocrinology and evolutionary genetics has occurred during the past two decades, resulting in the first direct documentation of genetic variation and correlation for endocrine regulators in nondomesticated animals. In a number of insect genetic polymorphisms (dispersal polymorphism in crickets, butterfly wing-pattern polymorphism), blood levels of ecdysteroids and juvenile hormone covary with morphology, development, and life history. Genetic variation in insulin signaling may underlie life history trade-offs in Drosophila. Vertebrate studies identified variation in brain neurohormones, bone-regulating hormones, and hormone receptor gene sequences that underlie ecologically important genetic polymorphisms. Most work to date has focused on genetically variable titers (concentrations) of circulating hormones and the activities of titer regulators. Continued progress will require greater integration among (a) traditional comparative endocrine approaches (e.g., titer measures); (b) molecular studies of hormone receptors and intracellular signaling pathways; and (c) fitness studies of genetically variable endocrine traits in ecologically appropriate conditions. 794 Zera e t a

Tissue and stage-specific juvenile hormone esterase (JHE) and epoxide hydrolase (JHEH) enzyme activities and Jhe transcript abundance in lines of the cricket Gryllus assimilis artificially selected for plasma JHE activity: Implications for JHE microevolution

“…Characterizing genetically-based endocrine variation within populations of organisms is one of the most important tasks facing the nascent field of evolutionary endocrinology (Zera et al, 2007).…”

“…segregating within populations of species. However, relatively little is known about the characteristics of this intraspecific endocrine variation, which, in turn, limits our understanding of the mechanisms underlying endocrine microevolution (Zera, 2006;Zera et al, 2007).…”

“…Juvenile hormone esterase (JHE) activity in species of Gryllus crickets has been intensively studied from an evolutionary-genetic perspective (reviewed in Zera, 2006;and Zera et al, 2007). JHE hydrolyzes the key developmental and reproductive hormone, juvenile hormone (JH), and partially regulates its titer (Hammock, 1985;Roe and Venkatesh, 1990;Goodman and Granger, 2005).…”

“…In wing-polymorphic species, elevated plasma JHE activity during the last nymphal stadium is strongly associated genetically with the subsequent production of the flight-capable (long-winged) as opposed to the flightless (short-winged)/reproductive morph (Zera and Tiebel, 1989;Roff et al, 1997;Zera and Huang, 1999). This strong association implicates selection on genetic variation for JHE activity as an important component of the evolution of flightlessness in Gryllus (reviewed in Zera, 2004;Zera, 2006;Zera et al, 2007 Tissue and stage-specific juvenile hormone esterase (JHE) and epoxide hydrolase (JHEH) enzyme activities and Jhe transcript abundance in lines of the cricket Gryllus assimilis artificially selected for plasma JHE activity: Implications for JHE microevolution…”

“…Thus far, our functional-genetic studies of JHE variation have focused almost exclusively on the characteristics, correlations and functional consequences of JHE activity in the plasma of artificially-selected lines of three Gryllus species (reviewed in Zera, 2006;Zera et al, 2007;Crone et al, 2007;see Section 4). Results to date collectively indicate that genetic alterations in JHE activity in the plasma during the last nymphal stadium (1) give rise to altered JH metabolism and expression of JH-regulated traits, and (2) likely result from variation in some aspect of JHE gene regulation rather than JHE allozymes that differ kinetically due to variation in primary amino acid sequence or posttranslational modification.…”