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Abstract Detail

Population Genetics

Pembrook III, James W. [1], Bruederle, Leo P. [1].

Population genetic diversity and structure in the edaphic endemic Carex scirpoidea subsp. convoluta (Cyperaceae).

Soil properties are considered second only to climatic factors in determining the origin and distribution of plant taxa. Consequently, the study of edaphic endemics can provide valuable insight into the role of natural selection in plant speciation, with edaphic endemics expected to have low levels of genetic variation relative to their widespread progenitors.  Carex section Scirpinae Tuck. (Cyperaceae) comprises a small group of predominantly North American sedges, several of which differ by their edaphic tolerances. As such, this section provides a model by which to study the evolution of edaphic endemics. We surveyed variation at 19 allozyme loci in order to quantify population genetic diversity and structure in the narrowly distributed, alvar-restricted Carex scirpoidea subsp. convoluta relative to its widespread conspecific C. scirpoidea subsp. scirpoidea, thereby controlling for life history traits such as breeding system. Data were collected from eight populations of C. scirpoidea subsp. scirpoidea from Alaska, Colorado, Minnesota, and Michigan, and six populations of Carex scirpoidea subsp. convoluta from Michigan and Ontario. Our data reveal relatively high levels of genetic diversity for all parameters analyzed when comparing Carex scirpoidea subsp. convoluta (e.g., He= 0.090) to the widespread C. scirpoidea subsp. scirpoidea (e.g., He= 0.077), with no statistically significant differences between means for the two subspecies.  However, Alaskan populations of C. scirpoidea subsp. scirpoidea exhibited levels of diversity that were twice as high than those observed in C. scirpoidea subsp. convoluta. As expected for an obligately outcrossing dioecious species, most loci were in Hardy-Weinberg Equilibrium (HWE), though heterozygote deficiency was observed for all loci not in HWE. As expected, population differentiation was significantly higher in the widespread C. scirpoidea subsp. scirpoidea (FST = 0.468) than C. scirpoidea subsp. convoluta (FST = 0.185; Nm = 0.793), revealing that populations of the narrow endemic are genetically more similar. Our results combined with other systematic data (e.g., chromosome number, nr- and cpDNA sequence variation) support the hypothesis that C. scirpoidea subsp. convoluta is a morphologically distinct ecotype of C. scirpoidea that is currently diverging as a result of natural selection imparted by soil chemistry, with fixation of neutral loci lagging behind morphological differentiation.

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1 - University Of Colorado Denver, CB171, P.O. 173364, DENVER, CO, 80217-3364, USA

population genetics
Edaphic Endemic
Narrow vs. Widespread
Carex scirpoidea

Presentation Type: Oral Paper:Papers for Topics
Session: 6
Location: Pines South/Boise Centre
Date: Monday, July 28th, 2014
Time: 11:00 AM
Number: 6010
Abstract ID:730
Candidate for Awards:Margaret Menzel Award

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