Environmental sex determination ESD is an ideal trait for assessing the evolutionary potential of organisms to respond to rapid environmental change. Google Scholar. In other words, how have conspecific populations with TSD currently occupying vastly different environments solved the sex-ratio problem?
Species that are unable to respond to anthropogenically induced environmental change, likely because of the unprecedented rate at which such environmental changes are occurring, may face extinction Palumbi The low repeatability in individual timing of nesting across years Schwanz and Janzen suggests that this behavior is not canalized or synchronized overall.
Age and season impact resource allocation to eggs and nesting behavior in the painted turtle.
Demographic factors and genetic variation influence population persistence under environmental change. Spencer and Janzen found that hatchlings from mixed-sex nests were less energy efficient and grew less than their same-sex counterparts incubated in single-sex producing temperatures.
Researchers counted, collected, and incubated second generation eggs across all years, recording which females bore which eggs, and taking tissue samples from each offspring for paternity analyses. In species for which the development of sex organs depends on the temperature of the environment, it is difficult to produce both sexes at temperatures that would naturally only produce one sex.
We also quantify vegetation cover directly over each nest using a spherical densiometer with readings taken from each of the 4 cardinal directions Janzen b or, more recently, using hemispherical photography Doody et al.
Adams Heritable variation for sex ratio under environmental sex determination in the common temperature dependent sex determination evolution definition in Lancashire turtle Chelydra serpentina.
Reproducing lizards modify sex allocation in response to operational sex ratios. Can J Zool. While aromatase activity remains low for much of development in individuals that exhibit TSD, during the thermosensitive period, variations in temperature increase the activity of aromatase.
Laboratory incubation experiments designed to test the effects of temperature on offspring sex ratio have traditionally been conducted using constant incubation temperatures, which may not accurately replicate the incubation conditions in natural nests that experience daily and seasonal fluctuations.