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Abstract Detail



A Colloquium Honoring Leslie D. Gottlieb

Baldwin, Bruce [1].

Contributions of Leslie D. Gottlieb and colleagues to understanding modes, rates, and genetics of evolutionary divergence in Layia (Compositae).

Gottlieb’s elegant studies with Vera Ford and Suzanne Warwick on Layia and related genera of Madiinae (Compositae) focused on fundamental questions concerning evolutionary modes and rates that are of growing interest today. Earlier work on the n=7 Layia taxa by Clausen, Keck, and Hiesey revealed patterns of interfertility and meiotic chromosomal pairing that led Stebbins to champion those plants as textbook examples of geographic speciation, with sympatry reflecting recontact after ancient allopatric divergence and accompanying gradual decay of interfertility. Warwick and Gottlieb’s subsequent examination of pairwise genetic identities across the n=7 group, based on results of enzyme electrophoresis, provided congruent and compelling evidence of much more extensive divergence among the three major (and sometimes sympatric) hypothesized lineages than expected for annuals that had evolved recently, whereas taxa within each of the three lineages appeared to have evolved recently. Their interpretations are fully corroborated by phylogenetic analyses of DNA sequence data, which indicate additional evidence of allopatric divergence within currently recognized taxa. In the major n=8 group of Layia taxa, Ford and Gottlieb’s evolutionary and genetic studies of the widespread L. glandulosa and the serpentine-endemic L. discoidea provide a premier example of rapid evolutionary change on serpentine soils and of divergence of a peripheral isolate. Their Mendelian genetic and protein electrophoretic studies of that taxon pair greatly extended the earlier work of Clausen, Keck, and Hiesey and overturned Clausen et al.’s suggestion that the serpentine endemic L. discoidea was an evolutionary relict. Instead, Ford and Gottlieb showed that L. discoidea was an example of recent divergence, probably from an ancestor within L. glandulosa, as corroborated later with DNA sequence data. Their genetic dissection of major morphological differences between L. glandulosa and L. discoidea, including presence or absence of ray flowers and associated phyllaries, showed in detail that morphological character differences that originally led L. discoidea to be mistaken as a member of a different tribe of Compositae had fairly simple genetic bases, in line with recent evolution of the serpentine endemic. My lab’s subsequent work on the main n=8 Layia lineage using DNA sequence data indicates another example of accelerated divergence in a marginal edaphic setting, in the dune-endemic L. carnosa, but with evolution of intersterility barriers between it and related taxa, unlike in L. discoidea, where complete interfertility with various populations of L. glandulosa readily allows for further detailed studies of trait evolution associated with the transition to serpentine ecology.

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1 - University of California Berkeley, JEPSON HERB & DEPT INTEGR BIOL, 1001 Valley Life Sciences Building, MC 2465, Berkeley, CA, 94720-2465, USA

Keywords:
Gottlieb
Asteraceae
Compositae
speciation
Layia
Madiinae
diversification
evolutionary rates.

Presentation Type: Symposium or Colloquium Presentation
Session: C1
Location: Grand Ballroom A/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 10:00 AM
Number: C1007
Abstract ID:939
Candidate for Awards:None


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