However, in the presence of the climate variables, bare ground and large trees were no longer significant. The production of sex hormones can result solely from genetics or from genetics in combination with the influence of environmental factors. Oikos doi: Pincheira-Donoso D, Tregenza T Fecundity selection and the evolution of reproductive output and sex-specific body size in the Liolaemus lizard adaptive radiation.
Journal of Evolutionary Biology. Sinauer Associates: Massachusetts. Spencer and Janzen found further support for the Charnov-Bull model by incubating painted turtles Chrysemys picta at different temperatures and measuring various characteristics indicative of fitness. Although other environmental influences can have similar effects, temperature is the most wide-spread factor that alters aromatase activity and sex determination.
Scientists are still working to understand the evolution of TSD and the implications of climate change for species that exhibit this mechanism of sex determination. Warner, Daniel, and Richard Shine. Read Now.
Administering estradiol at male-producing temperatures generates females that are physiologically identical to temperature-produced females.
Charnier observed that temperature affected sex ratios, which are the number of females versus males in a population or a single clutch of eggs, of the rainbow Agama lizard, Agama agama. Hatchlings from single-sex producing temperatures also had higher first-year survivorship than the hatchlings from the temperature that produces both sexes.
One possible explanation that TSD is common in amniotes is phylogenetic inertia — TSD is the ancestral condition in this clade and is simply maintained in extant lineages because it is currently adaptively neutral or nearly so.
Bull, James, and Richard Vogt. The production of sex hormones can result solely from genetics or from genetics in combination with the influence of environmental factors. At this point, little evidence supported TSD as a possible mode of sex determination.
Furthermore, we found SVL decreased as the percent cover of bare ground increased Figure 4c , and female SVL increased relative to the increase in the density of mature trees Figure 4d. And I can think of several ways in which we are likely to become extinct long before we run out of Y chromosome.
We used a statistical modeling approach to study relationships between lizard SVL for both sexes separately and candidate explanatory variables from the four domains; geography, climate, habitat and management. Forsman A, Lindell LE Resource dependent growth and body condition dynamics in juvenile snakes: an experiment.
Pincheira-Donoso D, Tregenza T Fecundity selection and the evolution of reproductive output and sex-specific body size in the Liolaemus lizard adaptive radiation.