page_title: Leslie D. Gottlieb
section_title: Quantum speciation
hierarchical_section_title: Leslie D. Gottlieb / Research / Quantum speciation
caption_attribution_description: English: Layia glandulosa — Whitedaisy tidytips. On Cima Dome near Teutonia Peak, Mojave National Preserve, Mojave Desert, California.
context_page_description: Leslie D. Gottlieb was a US biologist described by the Botanical Society of America as "one of the most influential plant evolutionary biologists over the past several decades.". He was employed at the University of California, Davis for 34 years, and published widely. In addition to his primary work in plant genetics, Gottlieb was an advocate for rare and endangered plant conservation.
context_section_description: Gottlieb was occupied with new species formation via "quantum speciation" throughout his career.   As defined by Verne Grant, and cited by Gottlieb in his 2003 summary of the subject in plants "we can define quantum speciation as the budding off of a new and very different daughter species from a semi-isolated peripheral population of the ancestral species in a cross-fertilizing organism...as compared with geographical speciation, which is a gradual and conservative process, quantum speciation is rapid and radical in its phenotypic or genotypic effects or both." Grant thought that it would be accompanied by inbreeding in the founder population.  Therefore, "quantum speciation" would be related to, if not identical with, in Gottlieb's use of the term, sympatric speciation.  In fact Gottlieb's first publication on "sympatric speciation" in Stephanomeria', published in 1971, was summarised by him in the above 2003 paper on "quantum speciation."  Gottlieb did not believe that sympatric speciation required disruptive selection to form a reproductive isolating barrier, as defined by Grant, and in fact Gottlieb stated that requiring disruptive selection was "unnecessarily restrictive" in identifying cases of sympatric speciation.
  In terminology used by Gottlieb, "progenitor species " would be the parental or "ancestral" species and the newly formed daughter species was "derived."
  In his first study of progenitor-derivative pairs of species, Gottlieb examined the diploid, geographically limited, self-pollinating derived species Stephanomeria malheurensis with the  diploid, geographically widespread obligate outcrossing ancestral species Stephanomeria exicua ssp. coronaria. In this case the reproductive isolating barrier was probably a change from outcrossing to selfing, and was maintained by this and a high degree of inter-specific sterility with ssp. coronaria as a result of chromosomal structural differences.  Using what was then the most modern molecular technique, starch gel electrophoresis, to determine the genetics of populations Gottlieb found that S. malheurensis had a subset of the genetic variability of ssp. coronaria.  This, as well as its geographical close proximity, led Gottlieb to propose that S. malhurensis was a product of "quantum speciation." Additionally, S. malheurensis was found to be much less adapted to the local habitat than ssp. coronaria (hence the name malhurensis, which in French, "Malheur" means unhappiness or misfortune), indicating that it was probably not formed by disruptive selection.
  In his second study of progenitor-derivative pairs of species, Gottlieb looked at the putative progenitor diploid Clarkia rubicunda and its hypothesized derivative, diploid C. franciscana. In 1958 Lews and Raven hypothesized that C. franciscana, which was highly self-pollinating and geographically limited, was derived from the outcrossing and more widespread C. rubicunda by large chromosomal structural rearrangements.  Lewis and Raven hypothesized that C. franciscana had rapidly speciated from C. rubicunda by a mechanism Harlan Lewis called "catastrophic selection."  As with Stephanomeria, Gottlieb hypothesized that if C. franciscana was a derived species by "rapid speciation," then the derived species should have a genetic compliment that is similar to its progenitor, "i.e., possess few novel alleles." In fact, Gottlieb found that C. franciscana was genetically distinct from C. rubicunda; it did not, as expected, have a subset of the genes found in C. rubicunda. A subsequent analysis published in 1992 on another population of C. franciscana, unknown to Gottlieb 20 years earlier, led to similar conclusions.  Importantly Gottlieb ended his 1973 study of C. franciscana by stating: "To strengthen phylogenetic analyses of rapid speciation, the criterion is proposed that a species accepted as having had a rapid and recent origin by chromosomal reorganization be substantially similar to its progenitor upon electrophoretic examination." In this context Gottlieb equated "electrophoretic examination" with genetic examinati
caption: Layia glandulosa
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