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Wolbachia and Sex Determination

By evolgen on April 19, 2007.

There are two cool articles on two related topics, but the articles themselves don't deal with the area in which these topic overlap. Confused? Here's a quick description of the two articles:

One article is on the change in fecundity cost of Wolbachia infections in a population of Drosophila simulans. Wolbachia are bacterial symbionts which can do all kinds of cool stuff to their hosts, including preventing infected males from mating with uninfected females (cytoplasmic incompatibility) and causing male zygotes to die before fully developing (male killing). Wolbachia can really do a number on sex ratios and can override chromosomal sex determination systems. Jonathan Eisen has more.

The other paper deals with sex determination in lizards (it's currently embargoed, but Nobel Intent has a summary). Different species of lizards use different mechanisms for sex determination (reviewed here), including XY, ZW, and temperature dependent. The authors of this study report that a species of lizard that uses a ZW system (males are ZZ and females are ZW) is also sensitive to temperature dependent sex determination. At high temperature (above 34°C) half of the ZZ individuals develop into females. This is a cool example of a mix between chromosomal and environmental sex determination.

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biology

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Interesting stuff. I think that Wolbachia is somewhat interesting in creation vs evolution debates as an example of how hybrid inviability is possible once the populations are independent, even tough I don't know whether cytoplasmic incompability is an usual reason of hybrid inviability or something else. Trying to join the topics myself, perhaps something Wolbachia-like could trigger a speciation into a unisexual species in some cases. Perhaps Wolbachia itself in their hosts, eventualy becoming a sort of endosymbiote.

On temperature dependent sex determination, I wonder if it may have sooner or later effects on extinction of species due to global warming. It was proposed a few times that the extinction of nonavian dinosaurs may have been at least partly due to that.

By Danniel Soares (not verified) on 20 Apr 2007 #permalink

Other people have proposed wolbachia induced reproductive isolation. I don't know if any of those studies have panned out.

Evolution is always ongoing. I think some people have observed uninfected populations become infected with Wolbachia. But I don't know when the first Wolbachia infected a Drosophila species.