Evolution and Development
Shapiro MD, Bell MA, Kingsley DM. 2006. Parallel genetic origins of pelvic reduction in vertebrates. Proc Natl Acad Sci U S A. 103(37):13753-8.
Chan YF, Marks ME, Jones FC, Villarreal G Jr, Shapiro MD, Brady SD, Southwick AM, Absher DM, Grimwood J, Schmutz J, Myers RM, Petrov D, Jónsson B, Schluter D, Bell MA, Kingsley DM. 2010. Adaptive evolution of pelvic reduction in sticklebacks by recurrent deletion of a Pitx1 enhancer. Science. 327(5963):302-5.
Briefly tell us a bit about yourself, your career path over the years, and specifically what led you to begin working on Sticklebacks as a model system to study evolution and development.
How can you know if the pelvic region was in the common ancestor and diminished throughout evolution or if the pelvic region was “created” over evolution as an adaptation mechanism?
The area that controls pelvic development is only a 23-kb region. This zone seems very small and therefore mutations would be less likely to occur. Why has it been found to be the opposite?
Since the deletion mutation at Pitx1 has high prevalence and is evidence for adaptive evolution, do you consider it as natural selection or balancing selection?
To what extent are the genetic mechanisms originally found in the studies about sticklebacks a broad generality? How can these mechanisms be used and extrapolated to include other animals that also have been noted to have pelvic reduction?
There is strong evidence that the Pel enhancer region is responsible for the tissue-specific expression of Pitx1 in the pelvis, but did you also look at other phenotypes that are discordant between marine and freshwater populations? Pitx1 expression depends on the Pel enhancer, but it may also depend on other transcription factors and signaling pathways. Is it possible that these other differing phenotypes can also have an effect on the larger signaling pathway of Pitx1 expression, and therefore account for some of the changes in expression pattern?
Why would fish that do not have these pelvic spines have the pel enhancer region? Do they have a different pelvic structure? And is pel always located near the telomere across species?
Why haven’t similar changes occurred in Pitx2 if it also controls hind limb morphologies?
It seems that in both sticklebacks and Manatees the directional asymmetry favors a larger left-side of the pelvis. In a behavioral and survival perspective, directional asymmetry does not seem like it would be a favorable adaptation, because it may alter swimming abilities, however the phenotype is present in many vertebrate species. Is there a positive evolutionary adaption for this phenotype? With basic analysis one would assume that natural selection would favor a more even pelvis, with or without a pelvic reduction.
Currently in your opinion what are the most pressing questions in the field of evolution and development, and what steps is your lab taking to address these questions?
Michael J.F. Barresi