[amplexity (OP)]

If sex is determined by temperature in reptiles, wouldn't whole generations of a species be the same sex, at least at the local scale?  For example, lets imagine lizards living in a particular stretch of flat desert.  Presumably, this area will be experiencing the same temperatures, and the lizards will be choosing the same type of areas to lay their eggs.  Because these eggs are all incubating at the same temperature, wouldn't this entire generation be of the same sex?  This would seem to complicate the search for appropriate mates in the future, especially for short-lived species.

[RD]

If sex is determined by temperature in reptiles, wouldn't whole generations of a species be the same sex, at least at the local scale?

How big is "local" ?

There will be microclimate variation due to different microhabitats* , e.g  variations in shade from nest to nest, variations in the thermal conductivity of the ground the eggs are on, if eggs are buried variations in the depth eggs are buried in the same or different nests, will all vary the temperature an egg experiences, even if the macroclimate was constant. 

[* not furniture stores for short people [] ]

[amplexity (OP)]

But has anybody ever quantified this (looked at sex ratios per generation)?

I would think that these microclimates/microhabitats wouldn't have a large effect, because the animals have a very specific requirement for nesting sites.  Some aren't going to nest in the shade while others nest in the sun.  Furthermore, many reptiles will nest in burrows underground, where temperatures are remarkably stable. 

[Bored chemist]

A "whole generation" is just 1 year. If the animals expect to live much longer than that it doesn't matter much.

[amplexity (OP)]

A "whole generation" is just 1 year. If the animals expect to live much longer than that it doesn't matter much.

Yes, I know.  That is why I originally said "for short-lived species"

[CliffordK]

It would seem that temperature variations on the scale of a decade or so would not be uncommon, so short-lived species would have to be able to adapt.

Perhaps the temperature set-point is variable, so the surviving males or females would quickly reset the set-point for the whole species.  Or some females will lay their eggs in deeper, and others in more shallow nests. 

There would be benefits if an entire nest would be the same sex, so that there might be less inbreeding, but certainly a problem if all nests were the same sex.

Here was a recent topic about dinosaurs and the potential for same sex offspring.
http://www.thenakedscientists.com/forum/index.php?topic=44810.0