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SUMMARY:Why is Wolbachia-induced cytoplasmic incompatibility so common? - 
 Professor Michael Turelli\, from Department of Evolution and Ecology\, UC 
 Davis College of Biological Sciences\, CA 
DTSTART:20220929T130000Z
DTEND:20220929T140000Z
UID:TALK177047@talks.cam.ac.uk
CONTACT:Caroline Newnham
DESCRIPTION:Cytoplasmic incompatibility (CI) is the most common reproducti
 ve manipulation produced by Wolbachia\, obligately intracellular alphaprot
 eobacteria that infect roughly half of all insect species. Once infection 
 frequencies within host populations approach 10%\, intense CI can drive Wo
 lbachia to near fixation within 10 generations. However\, natural selectio
 n among Wolbachia variants within individual host populations does not fav
 or enhanced CI. Indeed\, variants that do not cause CI\, but increase host
  fitness\, are expected to spread –– if infected females remain protec
 ted from CI (Turelli 1994). Nevertheless\, roughly half of analyzed Wolbac
 hia infections cause detectable CI. Why? The frequency and persistence of 
 CI is more plausibly explained by preferential spread to new host species 
 rather than preferential spread within host populations (i.e.\, classical 
 natural selection). CI-causing Wolbachia variants preferentially spread in
 to new host species because: 1) CI increases equilibrium Wolbachia frequen
 cies within populations\, and 2) CI-causing variants can remain at high fr
 equencies even when conditions change so that initially beneficial Wolbach
 ia infections become harmful. In contrast\, CI does little to help establi
 sh beneficial Wolbachia in new host species. An epidemiological model desc
 ribing Wolbachia acquisition and loss by host species and the loss of CI-i
 nduction within Wolbachia lineages yields simple expressions for the incid
 ence of Wolbachia infections and the fraction of those infections causing 
 CI. Supporting a determinative role for differential interspecific spread 
 in maintaining CI\, many Wolbachia infections were recently acquired by th
 eir host species\, many show evidence for contemporary spatial spread or r
 etreat\, and rapid evolution of CI-inducing loci\, especially degradation\
 , is common.
LOCATION:Zoom meeting
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